TY - CONF TI - Role of micro-/nanocrystalline structure in oxidation of FE-CR alloys AU - Singh Raman Rajeev, R.K. AU - Gupta, K. AU - Atanacio, A.J. AU - Prince, K. AU - Koch, C.C. C2 - 2008/// C3 - 48th Annual Conference of the Australasian Corrosion Association 2008: Corrosion and Prevention 2008 DA - 2008/// SP - 603-609 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84867738362&partnerID=MN8TOARS ER - TY - CONF TI - Low temperature oxidation of nanocystalline vis-à-vis microcrystalline Fe-Cr alloys AU - Singh Raman, R.K. AU - Gupta, R.K. AU - Koch, C.C. C2 - 2008/// C3 - 17th International Corrosion Congress 2008: Corrosion Control in the Service of Society DA - 2008/// VL - 5 SP - 3262-3269 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84865012025&partnerID=MN8TOARS ER - TY - CONF TI - Grain growth behaviour and consolddation of ball milled nanocrystalline iron-chromium alloys AU - Gupta, R.Kr. AU - Raman, R.K.S. AU - Koch, C.C. C2 - 2008/// C3 - TMS Annual Meeting DA - 2008/// VL - 1 SP - 151-157 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-53949111826&partnerID=MN8TOARS ER - TY - CONF TI - SYNTHESIS OF CERAMIC EUTECTICS USING MICROWAVE PROCESSING AU - Polotai, AV AU - Cheng, J AU - Agrawal, DK AU - Dickey, EC AU - Cytron, S C2 - 2008/// C3 - Ceramic Engineering and Science Proceedings DA - 2008/// VL - 25 SP - 127-+ M1 - 5 ER - TY - CONF TI - Ceramic-electrode interfaces in cofired electroceramic multilayer components AU - Randall, CA AU - Polotai, AV AU - Yang, GY AU - Dickey, EC C2 - 2008/12/1/ C3 - A Global Road Map for Ceramic Materials and Technologies: Forecasting the Future of Ceramics, International Ceramic Federation - 2nd International Congress on Ceramics, ICC 2008, Final Programme DA - 2008/12/1/ ER - TY - CONF TI - Stability of Ni electrodes and Ni-BaTiO3 interface evolution in ultrathin BME MLCCs AU - Polotai, AV AU - Shay, DP AU - Yang, GY AU - Dickey, EC AU - Randall, CA AB - Microstructural control in thin-layer multilayer ceramic capacitors (MLCC) is one of the present day challenges for maintaining an increase in capacitive volumetric efficiency. It is observed that the continuity of the Ni electrodes increases with increasing heating rate but behaves non-linearly on sintering temperature. It is proposed that an interfacial liquid alloy layer initiates when the Ni electrodes are under tension. This accelerates a stress-induced diffusion which is the key cause of the severe electrode discontinuities during heating. Kinetic and thermodynamic approaches based on the control of sintering profiles or the control of Ni-BaTiO3 interface chemistry are proposed to prevent the Ni electrode discontinuity. C2 - 2008/12/1/ C3 - IEEE International Symposium on Applications of Ferroelectrics DA - 2008/12/1/ DO - 10.1109/ISAF.2008.4693884 VL - 1 SP - 3-4 UR - https://app.dimensions.ai/details/publication/pub.1095119126 ER - TY - CONF TI - 23b. Growth characteristics and properties of Si and Si1-xGex nanowires AU - Nimmatoori, P AU - Zhang, Q AU - Zhang, X AU - Dickey, EC AU - Redwing, JM C2 - 2008/1/1/ C3 - Nanoscale Science and Engineering Forum Conference, Presentations at the 2008 AIChE Spring National Meeting DA - 2008/1/1/ SP - 26-32 ER - TY - CONF TI - Analysis of Compositionally and Structurally Graded Si:H and Si1-xGex:H Thin Films by Real Time Spectroscopic Ellipsometry AU - Podraza, NJ AU - Li, J AU - Wronski, CR AU - Horn, MW AU - Dickey, EC AU - Collins, RW C2 - 2008/// C3 - MRS Online Proceedings Library DA - 2008/// DO - 10.1557/PROC-1066-A10-01 VL - 1066 SP - 253-+ UR - https://app.dimensions.ai/details/publication/pub.1067906026 ER - TY - CONF TI - 23b. Growth characteristics and properties of Si and Si 1-xGex nanowires AU - Nimmatoori, P AU - Zhang, Q AU - Zhang, X AU - Dickey, EC AU - Redwing, JM C2 - 2008/11/26/ C3 - AIChE Annual Meeting, Conference Proceedings DA - 2008/11/26/ ER - TY - CONF TI - "Pot-in-pot" reactions: Site-isolation of organometallic catalysts from each other for versatile cascade reactions and catalyst recycling AU - Mwangi, M.T. AU - Runge, M.B. AU - Bowden, N.B. T2 - 235th ACS National Meeting C2 - 2008/// C3 - 235th ACS National Meeting CY - New Orleans, LA, United States DA - 2008/// PY - 2008/4/6/ ER - TY - CONF TI - "Pot-in-pot" reactions: Polymers macro- fabrication for site-isolation of catalysts and reagents AU - Mwangi, M.T. AU - Runge, M.B. AU - Bowden, N.B. T2 - AIChE Spring National Meeting C2 - 2008/// C3 - AIChE Spring National Meeting CY - New Orleans, LA, United States DA - 2008/// PY - 2008/4/6/ ER - TY - JOUR TI - Repellent Properties of δ-Octalactone Against the Tsetse Fly, Glossina morsitans Morsitans AU - Mwangi, M. AU - Thuo, M. AU - Gikonyo, Nicholas K. AU - Ndiege, Isaiah O. T2 - Journal of Insect Science AB - δ-octalactone, produced by several Bovidae, has been suggested as a potential repellant of tsetse fly attack. Racemic δ-octalactone was synthesized via an abbreviated route. The product was assayed against 3-day old starved teneral female tsetse flies, Glossina morsitans morsitans Wiedemann (Diptera: Glossinidae), in a choice wind tunnel and found to be a potent tsetse repellent at doses ≥0.05 mg in 200 μl of paraffin oil (0.05 >p >0.01). DA - 2008/5// PY - 2008/5// DO - 10.1673/031.008.4301 VL - 8 IS - 1 SP - 43 SN - 1536-2442 UR - http://dx.doi.org/10.1673/031.008.4301 KW - allomone KW - bioassay KW - choice wind tunnel KW - olfaction KW - racemic delta-octalactone synthesis ER - TY - JOUR TI - Femtosecond laser induced coordination transformation and migration of ions in sodium borate glasses AU - Liu, Y. AU - Zhu, B. AU - Wang, L. AU - Qiu, J. AU - Dai, Y. AU - Ma, H. T2 - Applied Physics Letters AB - We report on the coordination transformation of B3+ ions and migration of Na+ and O2− ions in sodium borate glasses, induced by 250kHz, 800nm femtosecond laser irradiation. Micro-Raman spectra show that the ratio of the integrated intensity of the two peaks at 806 and 774cm−1 decreases at first and then increases with increasing distance from the center of the laser modified zone. Electron dispersive x-ray spectra show that a portion of Na+ and O2− ions migrate from the vicinity of focal point after the femtosecond laser irradiation. A possible mechanism is proposed to explain the observed phenomena. DA - 2008/// PY - 2008/// DO - 10.1063/1.2903710 VL - 92 SP - 121113 ER - TY - JOUR TI - Co-operative downconversion luminescence in Tm3+/Yb3+ : SiO2–Al2O3–LiF–GdF3 glasses AU - Lakeshiminarayana, G. AU - Yang, H. AU - Ye, S. AU - Liu, Y. AU - Qiu, J. T2 - Journal of Physics D: Applied Physics AB - Oxyfluoride aluminosilicate glasses in the composition of 50SiO2–20Al2O3–20LiF–10GdF3–0.5TmF3–xYbF3 (x = 0, 1.0, 2.5, 5, 7.5, 10, 15, 20, 25 and 30 mol%) have been prepared to study their thermal and optical properties. From the differential thermal analysis measurements, glass transition temperatures and onset crystallization temperatures have been evaluated and from them glass stability factors were calculated. Glass stabilities decreased gradually with fluoride content increment in all the studied glasses. The photoluminescence and decay measurements have also been carried out for all these glasses. In these glasses, an efficient near infrared quantum cutting with optimal quantum efficiency approaching 187% has been demonstrated, by exploring the co-operative downconversion mechanism from Tm3+ to Yb3+, with 467 nm (Tm3+ : 3H6 → 1G4) excitation wavelength. These glasses are promising materials to achieve high efficiency silicon based solar cells by means of downconversion in the visible part of the solar spectrum. DA - 2008/// PY - 2008/// DO - 10.1088/0022-3727/41/17/175111 VL - 41 IS - 17 SP - 175111 ER - TY - JOUR TI - Femtosecond laser direct writing of crystalline TiO2 patterns in glass AU - Liu, Y. AU - Zhu, B. AU - Wang, L. AU - Dai, Y. AU - Ma, H. AU - Lakshminarayana, G. AU - Qiu, J. T2 - Applied Physics. B: Lasers and Optics DA - 2008/// PY - 2008/// DO - 10.1007/s00340-008-3166-4 VL - 93 SP - 613-617 KW - 42 KW - 62 KW - -b KW - 78 KW - 30 KW - -j KW - 65 KW - 60 KW - +a ER - TY - JOUR TI - Cooperative downconversion luminescence in Pr3+/Yb3+:SiO2–Al2O3–BaF2–GdF3 glasses AU - Lakshminarayana, G. AU - Yang., H. AU - Ye., S. AU - Liu., Y. AU - Qiu, J. T2 - Journal of Materials Research DA - 2008/// PY - 2008/// DO - 10.1557/jmr.2008.0372 VL - 23 SP - 3090–3095 ER - TY - JOUR TI - Multiferroics and magnetoelectrics: thin films and nanostructures AU - Martin, L. W. AU - Crane, S. P. AU - Chu, Y. H. AU - Holcomb, M. B. AU - Gajek, M. AU - Huijben, M. AU - Yang, C. H. AU - Balke, N. AU - Ramesh, R. T2 - Journal of Physics-Condensed Matter AB - Multiferroic materials, or materials that simultaneously possess two or more ferroic order parameters, have returned to the forefront of materials research. Driven by the desire to achieve new functionalities—such as electrical control of ferromagnetism at room temperature—researchers have undertaken a concerted effort to identify and understand the complexities of multiferroic materials. The ability to create high quality thin film multiferroics stands as one of the single most important landmarks in this flurry of research activity. In this review we discuss the basics of multiferroics including the important order parameters and magnetoelectric coupling in materials. We then discuss in detail the growth of single phase, horizontal multilayer, and vertical heterostructure multiferroics. The review ends with a look to the future and how multiferroics can be used to create new functionalities in materials. DA - 2008/// PY - 2008/// DO - 10.1088/0953-8984/20/43/434220 VL - 20 IS - 43 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000259922600021&KeyUID=WOS:000259922600021 ER - TY - JOUR TI - Migration of Charged Defects in Local Depolarization Fields as a Mechanism of Aging in Ferroelectrics AU - Genenko, Y. A. AU - Balke, N. AU - Lupascu, D. C. T2 - Ferroelectrics AB - Quasistatic dielectric relaxation due to migration of charged point defects is considered as a mechanism of aging in ferroelectrics. A two-dimensional model is developed which includes the coupled potential problem and the field-driven diffusion problem. Numerical study reveals formation of space charge zones near the grain boundaries with the only characteristic time of several days being the Maxwell relaxation time defined by the charge carrier density and mobility. The clamping pressure due to charge segregation is about few MPa which corresponds to observed coercive stresses in perovskite ferroelectrics and is significantly stronger than in the mechanisms involving orientational reordering of defect dipoles. DA - 2008/// PY - 2008/// DO - 10.1080/00150190802381563 VL - 370 SP - 196-202 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000260641100025&KeyUID=WOS:000260641100025 ER - TY - CHAP TI - CH003: Stability of nanodots in ferroelectric thin films AU - Balke, N. AU - Yu, P. AU - Wang, L. P. AU - Ramesh, R. AU - Ieee T2 - 2008 17th Ieee International Symposium on the Applications of Ferroelectrics PY - 2008/// SP - 69-70 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000270584000022&KeyUID=WOS:000270584000022 ER - TY - JOUR TI - Electric-field control of local ferromagnetism using a magnetoelectric multiferroic (vol 7, pg 478, 2008) AU - Chu, Ying-Hao AU - Martin, Lane W. AU - Holcomb, Mikel B. AU - Gajek, Martin AU - Han, Shu-Jen AU - He, Qing AU - Balke, Nina AU - Yang, Chan-Ho AU - Lee, Donkoun AU - Hu, Wei AU - Zhan, Qian AU - Yang, Pei-Ling AU - Fraile-Rodriguez, Arantxa AU - Scholl, Andreas AU - Wang, Shan X. AU - Ramesh, R. T2 - Nature Materials AB - Nature Materials 7, 478–482 (2008) The authors wish to correct Fig. 6 of this article, where they had incorrectly depicted the incoming X-ray direction; this does not alter the interpretation of the data presented. The correct figure is shown below. DA - 2008/// PY - 2008/// DO - 10.1038/nmat2246 VL - 7 IS - 8 SP - 678 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000257892200029&KeyUID=WOS:000257892200029 ER - TY - JOUR TI - Current-voltage characteristics for lead zirconate titanate bulk ceramics AU - Balke, Nina AU - Granzow, Torsten AU - Roedel, Juergen T2 - Journal of Applied Physics AB - Current-voltage characteristics have been obtained on lead zirconate titanate bulk ceramics using robust measurement techniques separating polarization effects from actual charge transport. Measurement of the electrical conduction upon both increase and decrease in the electric field shows that long settling times are required to suppress polarization currents and obtain reliable data. The influence of additional field cycles and different electrode materials is also studied. The analysis reveals that an Ohmic conduction is dominant at low fields, while at high fields charge transport is most likely governed by space charge limited currents. DA - 2008/// PY - 2008/// DO - 10.1063/1.2976304 VL - 104 IS - 5 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000259853600106&KeyUID=WOS:000259853600106 ER - TY - JOUR TI - Electric-field control of local ferromagnetism using a magnetoelectric multiferroic AU - Chu, Ying-Hao AU - Martin, Lane W. AU - Holcomb, Mikel B. AU - Gajek, Martin AU - Han, Shu-Jen AU - He, Qing AU - Balke, Nina AU - Yang, Chan-Ho AU - Lee, Donkoun AU - Hu, Wei AU - Zhan, Qian AU - Yang, Pei-Ling AU - Fraile-Rodriguez, Arantxa AU - Scholl, Andreas AU - Wang, Shan X. AU - Ramesh, R. T2 - Nature Materials DA - 2008/// PY - 2008/// DO - 10.1038/nmat2184 VL - 7 IS - 6 SP - 478-482 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000256110200022&KeyUID=WOS:000256110200022 ER - TY - CHAP TI - CHO15: Current-voltage characteristics for PZT ceramics AU - Balke, N. AU - Granzow, T. AU - Roedel, J. AU - Ieee T2 - 2008 17th Ieee International Symposium on the Applications of Ferroelectrics PY - 2008/// SP - 91-92 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000270584000031&KeyUID=WOS:000270584000031 ER - TY - JOUR TI - Cascade reactions using LiAlH4 and Grignard reagents in the presence of water AU - Runge, M. Brett AU - Mwangi, Marin T. AU - Miller, A. Lee, II AU - Perring, Mathew AU - Bowden, Ned B. T2 - Angew. Chem., Int. Ed. AB - Divided we stand, together we fall: Incompatible reagents, such as water and LiAlH4, Grignard, or cuprate reagents, can be site-isolated on either side of a polydimethylsiloxane (PDMS) thimble (see scheme; SDS=sodium docecyl sulfate) for cascade reactions. The hydrophobic nature of the PDMS membrane prohibits polar molecules, such as water, from diffusing across the membrane. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z703002_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2008/// PY - 2008/// DO - 10.1002/anie.200703002 VL - 47 IS - 5 SP - 935-939 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000252651200024&KeyUID=WOS:000252651200024 KW - Grignard reagents KW - membranes KW - multicomponent reactions KW - site-isolation KW - synthetic methods ER - TY - JOUR TI - A materials approach to site-isolation of Grubbs catalysts from incompatible solvents and m-chloroperoxybenzoic acid AU - Mwangi, Martin T. AU - Runge, M. Brett AU - Hoak, Kevin M. AU - Schulz, Michael D. AU - Bowden, Ned B. T2 - Chem. - Eur. J. AB - Abstract The development of a method for site‐isolation of Grubbs second‐generation catalyst from MCPBA is described. In these reactions, Grubbs catalyst was dissolved in a solvent consisting of a mixture (1:1 v/v) of 1‐butyl‐3‐methylimidazolium hexafluorophosphate and methylene chloride and completely encapsulated within a thimble fabricated from polydimethylsiloxane (PDMS). A series of molecules that react by cross metathesis or ring‐closing metathesis were added to the interior of the thimble and allowed to react. In the last step, m‐ chloroperoxybenzoic acid (MCPBA) dissolved in MeOH/H 2 O (1:1 v/v) was added to the exterior of the PDMS thimble. Small organic molecules diffused through the PDMS to react with MCPBA to form epoxides, but the Grubbs catalyst remained encapsulated. This result is important because Grubbs catalyst catalytically decomposes MCPBA at ratios of MCPBA to Grubbs of 3000 to 1. The yields for this two‐step cascade sequence ranged from 67 to 83 %. The concept behind this sequence is that small organic molecules have high flux through PDMS but large molecules—such as Grubbs catalyst—and ionic reagents—such as MCPBA—have much lower flux through PDMS. Small molecules can thus react both outside and inside PDMS thimbles, whereas incompatible catalysts and reagents remain site‐isolated from each other. This method does not require alteration of structures of the catalysts or reagents, so it may be applied to a wide range of homogeneous catalysts and reagents. To demonstrate further that the catalyst was encapsulated, the Grubbs catalyst was successfully recycled within the cascade sequence. DA - 2008/// PY - 2008/// DO - 10.1002/chem.200800094 VL - 14 IS - 22 SP - 6780-6788 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000258217000025&KeyUID=WOS:000258217000025 KW - cascade reactions KW - epoxidation KW - metathesis KW - recycling ER - TY - JOUR TI - Ferroelastic domain switching fatigue in lead zirconate titanate ceramics AU - Pojprapai (Imlao), Soodkhet AU - Jones, Jacob L. AU - Studer, Andrew J. AU - Russell, Jennifer AU - Valanoor, Nagarajan AU - Hoffman, Mark T2 - Acta Materialia AB - The influence of the frequency and amplitude of cyclic mechanical loading on soft, tetragonal lead zirconate titanate (PZT) ceramics was investigated via neutron diffraction. Intensity change in the {2 0 0} reflections provided quantitative measurements of domain switching behavior, domain texture and the strain resulting from domain switching. The results are explained using a viscoelasticity model. It was found that the magnitude of applied stress affects the level of strain accumulated, while its frequency affects the time taken for the strain to reach saturation. Furthermore, markedly different behaviors are exhibited by poled and unpoled samples. For samples loaded under identical conditions, the frequency effect is more pronounced in unpoled samples and the accumulated ferroelastic strain is greater in poled samples. DA - 2008/4// PY - 2008/4// DO - 10.1016/j.actamat.2007.11.044 VL - 56 IS - 7 SP - 1577-1587 J2 - Acta Materialia LA - en OP - SN - 1359-6454 UR - http://dx.doi.org/10.1016/j.actamat.2007.11.044 DB - Crossref KW - electroceramics KW - piezoelectricity KW - neutron diffraction KW - fatigue test KW - ferroelastic ER - TY - JOUR TI - High-throughput evaluation of domain switching in piezoelectric ceramics and application to PbZr0.6Ti0.4O3 doped with La and Fe AU - Jones, Jacob L. AU - Pramanick, Abhijit AU - Daniels, John E. T2 - Applied Physics Letters AB - A combinatorial material synthesis and characterization technique is introduced and demonstrated wherein the ferroelectric behavior of a compositionally graded bulk ceramic is investigated during electrical loading. Using combined high-energy x-ray microdiffraction and fluorescence spectroscopy, non-180° domain wall motion of different compositions is measured and quantified as a function of composition across the gradation. The greatest amount of non-180° domain wall motion is found in samples containing the highest measured fraction of La dopant (2mol%). DA - 2008/10/13/ PY - 2008/10/13/ DO - 10.1063/1.2999623 VL - 93 IS - 15 SP - 152904 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2999623 DB - Crossref ER - TY - JOUR TI - Nanoporous materials for biomedical devices AU - Adiga, Shashishekar P. AU - Curtiss, Larry A. AU - Elam, Jeffrey W. AU - Pellin, Michael J. AU - Shih, Chun-Che AU - Shih, Chun-Ming AU - Lin, Shing-Jong AU - Su, Yea-Yang AU - Gittard, Shaun D. AU - Zhang, Junping AU - Narayan, Roger J. T2 - JOM DA - 2008/3// PY - 2008/3// DO - 10.1007/s11837-008-0028-9 VL - 60 IS - 3 SP - 26-32 J2 - JOM LA - en OP - SN - 1047-4838 1543-1851 UR - http://dx.doi.org/10.1007/s11837-008-0028-9 DB - Crossref ER - TY - JOUR TI - Growth-Temperature-Controlled Optical Properties of Textured Mg x Zn1−x O Thin Films AU - Wei, W. AU - Jin, C. AU - Narayan, R.J. T2 - Journal of Electronic Materials DA - 2008/12/30/ PY - 2008/12/30/ DO - 10.1007/s11664-008-0613-2 VL - 38 IS - 4 SP - 613-617 J2 - Journal of Elec Materi LA - en OP - SN - 0361-5235 1543-186X UR - http://dx.doi.org/10.1007/s11664-008-0613-2 DB - Crossref KW - Magnesium zinc oxide KW - pulsed laser deposition KW - thin films KW - optical properties ER - TY - JOUR TI - Foreword AU - Narayan, Roger Jagdish T2 - Materials Science and Engineering: C DA - 2008/1// PY - 2008/1// DO - 10.1016/S0928-4931(07)00262-7 VL - 28 IS - 1 SP - vii J2 - Materials Science and Engineering: C LA - en OP - SN - 0928-4931 UR - http://dx.doi.org/10.1016/S0928-4931(07)00262-7 DB - Crossref ER - TY - JOUR TI - Recent progress in CAD/CAM laser direct-writing of biomaterials AU - Harris, M.L. AU - Doraiswamy, A. AU - Narayan, R.J. AU - Patz, T.M. AU - Chrisey, D.B. T2 - Materials Science and Engineering: C AB - The matrix-assisted pulsed-laser evaporation direct-write (MAPLE DW) process allows for computer-controlled deposition and machining of mesoscopic voxels of material with a high degree of spatial resolution. This article provides a review of current biomedical research activities that involve patterning of three-dimensional structures using the MAPLE DW process. Recent developments in microfabrication of hydroxyapatite-osteoblast-like cell composites, laser micromachining of differentially adherent substrates, and the influence of processing parameters (e.g., laser energy density and spot size) are discussed. The MAPLE DW process may be used to fabricate free-standing cell-seeded networks with unique geometries for tissue engineering, drug discovery, and other biomedical applications. DA - 2008/4// PY - 2008/4// DO - 10.1016/j.msec.2007.04.013 VL - 28 IS - 3 SP - 359-365 J2 - Materials Science and Engineering: C LA - en OP - SN - 0928-4931 UR - http://dx.doi.org/10.1016/j.msec.2007.04.013 DB - Crossref KW - tissue microfabrication KW - matrix-assisted pulsed-laser evaporation direct-write KW - CAD/CAM laser micromachining KW - biomaterials ER - TY - JOUR TI - Preface AU - Zhu, Yuntian AU - Estrin, Yuri AU - Langdon, Terence G. AU - Liao, Xiaozhou AU - Lowe, Terry C. AU - Shan, Zhiwei AU - Valiev, Ruslan Z. T2 - Journal of Materials Science DA - 2008/12// PY - 2008/12// DO - 10.1007/s10853-008-2991-5 VL - 43 IS - 23-24 SP - 7255-7256 J2 - J Mater Sci LA - en OP - SN - 0022-2461 1573-4803 UR - http://dx.doi.org/10.1007/s10853-008-2991-5 DB - Crossref ER - TY - JOUR TI - Plasma plume dynamics in magnetically assisted pulsed laser deposition AU - Haverkamp, J D AU - Bourham, M A AU - Du, S AU - Narayan, J T2 - Journal of Physics D: Applied Physics AB - The expansion of a laser produced plasma perpendicular to a magnetic field is studied with a quadruple Langmuir probe and a B-dot probe. In regions where the kinetic beta is less than one, we find plume deceleration and weak displacement of the magnetic field. As the plume expands into regions of weak magnetic field, plume deceleration stops and the displacement of the magnetic field is large. The diffusion time of the magnetic field lines was consistent with anomalously large resistivity driven by the presence of an instability. Electron temperatures are larger than in the field-free case due to Ohmic heating mediated by the anomalously large resistivity. DA - 2008/12/18/ PY - 2008/12/18/ DO - 10.1088/0022-3727/42/2/025201 VL - 42 IS - 2 SP - 025201 J2 - J. Phys. D: Appl. Phys. OP - SN - 0022-3727 1361-6463 UR - http://dx.doi.org/10.1088/0022-3727/42/2/025201 DB - Crossref ER - TY - JOUR TI - A novel technique for synthesizing MgB2thin films with high upper critical fields AU - Shen, Y AU - Gandikota, R AU - Singh, R K AU - Hunte, F L AU - Jaroszynski, J AU - Larbalestier, D C AU - Rowell, J M AU - Newman, N T2 - Superconductor Science and Technology AB - We report a new method for synthesizing magnesium diboride (MgB2) thin films which exhibit a steep increase in the slope of the upper critical field Hc2 versus decreasing temperature (i.e. |dHc2/dT|Tc|≈2.5 T K−1). An Hc2 of 38.4 T at 4.2 K and an extrapolated value of Hc2(0) above 43 T at 0 K are reported. Films of magnesium plus boron were deposited on unheated c-plane sapphire substrates by co-evaporation, and were subsequently annealed in a reducing atmosphere at temperatures below 600 °C. The use of a combination of a magnesium-rich stoichiometry (Mg/B>1/2) for the as-deposited film and a two-step annealing process was found to be critical in obtaining these high values of Hc2 and |dHc2/dT|Tc|. DA - 2008/5/30/ PY - 2008/5/30/ DO - 10.1088/0953-2048/21/8/085009 VL - 21 IS - 8 SP - 085009 J2 - Supercond. Sci. Technol. OP - SN - 0953-2048 1361-6668 UR - http://dx.doi.org/10.1088/0953-2048/21/8/085009 DB - Crossref ER - TY - JOUR TI - Development and prospects of nitride materials and devices with nonpolar surfaces AU - Paskova, Tanya T2 - physica status solidi (b) AB - Abstract The quest to use nonpolar surfaces of nitride materials and devices started a few years ago with the aim to avoid the strong internal electric fields in active regions of optoelec‐tronic devices and to improve their efficiency. Starting with the growth optimizations, the progression via thorough understanding of new physical properties of the materials has led to significant improvement of device performance and to novel device concepts. In this review a historical survey of nonpolar nitride growth achievements is made. Along the way new challenges in material growth and characterization have been encountered and more sophisticated methods have been developed, which are briefly summarized. The main properties of the nitride materials grown in nonpolar directions are discussed with emphasis on the deviations from those of nitrides grown along the polar direction. Physical phenomena such as inherently present anisotropic in‐plane strain and optical polarization anisotropy have been proposed for the realization of novel polarized light‐emitting diodes, polarization‐sensitive detectors and modulators. The present status of the nitride devices with nonpolar and semipolar surfaces is discussed, and an outlook of the future trends is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2008/6// PY - 2008/6// DO - 10.1002/pssb.200743274 VL - 245 IS - 6 SP - 1011-1025 J2 - phys. stat. sol. (b) LA - en OP - SN - 0370-1972 1521-3951 UR - http://dx.doi.org/10.1002/pssb.200743274 DB - Crossref ER - TY - JOUR TI - Coupled molecular dynamics/continuum simulations of Joule heating and melting of isolated copper–aluminum asperity contacts AU - Irving, D L AU - Padgett, C W AU - Brenner, D W T2 - Modelling and Simulation in Materials Science and Engineering AB - Atomic-level dynamics of Joule heating, melting and plastic dynamics at loaded nanometer-scale Cu and Al asperity contacts are modeled using an ad hoc coupling between a numerical solution to a heat transport equation, a virtual resistor network for describing electric current flow and a molecular dynamics simulation using the embedded atom method. Under constant voltage conditions the simulations demonstrate the formation of an Al melt that removes faceting from a Cu asperity via surface disordering at the melt–solid interface. Constant current simulations demonstrate initial disordering of both copper and aluminum at the interface. Flow from the aluminum melt increases the contact area, which lowers the resistance and drops the voltage to below that needed for melting. For the system with a loaded copper asperity, the interface recrystallizes and the dynamics transition from molten flow to plastic damage via dislocation emission. For an aluminum asperity, the asperity remains disordered after the voltage drop and no dislocation emission occurs into the copper or aluminum substrate. DA - 2008/11/18/ PY - 2008/11/18/ DO - 10.1088/0965-0393/17/1/015004 VL - 17 IS - 1 SP - 015004 J2 - Modelling Simul. Mater. Sci. Eng. OP - SN - 0965-0393 1361-651X UR - http://dx.doi.org/10.1088/0965-0393/17/1/015004 DB - Crossref ER - TY - JOUR TI - Magnetotransport of One-Dimensional Chains of CoFe2O4 Nanoparticles Ordered along DNA AU - Kinsella, Joseph M. AU - Ivanisevic, Albena T2 - The Journal of Physical Chemistry C AB - We have investigated the magnetotransport properties of 5 nm CoFe2O4 nanoparticles aligned into one-dimensional chains using a DNA guide. The chemically synthesized particles were capped with a positively charged ligand molecule that drives the electrostatic assembly when incubated in solutions containing DNA. To test the transport, these nanoparticle-coated DNA strands were adsorbed onto microfabricated devices. Large room-temperature magnetoresistance is observed at high fields in these samples. DA - 2008/3// PY - 2008/3// DO - 10.1021/jp712002a VL - 112 IS - 9 SP - 3191–3193 SN - 1932-7447 1932-7455 UR - http://dx.doi.org/10.1021/jp712002a ER - TY - JOUR TI - High efficiency blue phosphorescent organic light-emitting device AU - Chopra, Neetu AU - Lee, Jaewon AU - Zheng, Ying AU - Eom, Sang-Hyun AU - Xue, Jiangeng AU - So, Franky T2 - Applied Physics Letters AB - We have demonstrated a substantial enhancement in the efficiency of iridium (III) bis[(4,6-di-fluorophenyl)-pyridinate-N,C2′]picolinate based blue phosphorescent organic light-emitting devices (PHOLEDs). The efficiencies of PHOLEDs with conventional electron transport materials are low due to their low electron mobilities as well low triplet energies. High triplet energy electron transporting material with high electron mobility was used as a hole blocker to achieve efficient exciton confinement and good charge balance in the device thereby achieving a high current efficiency of 49cd∕A and an external quantum efficiency of 23%. DA - 2008/10/6/ PY - 2008/10/6/ DO - 10.1063/1.3000382 VL - 93 IS - 14 SP - 143307 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3000382 DB - Crossref ER - TY - JOUR TI - Low voltage and very high efficiency deep-blue phosphorescent organic light-emitting devices AU - Eom, Sang-Hyun AU - Zheng, Ying AU - Chopra, Neetu AU - Lee, Jaewon AU - So, Franky AU - Xue, Jiangeng T2 - Applied Physics Letters AB - We report on very high efficiency deep-blue phosphorescent organic light-emitting devices (PHOLEDs) based on iridium(III) bis(4′,6′-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6). Dual emissive layers consisting of an N,N′-dicarbazolyl-3,5-benzene layer doped with 4wt% FIr6 and a p-bis(triphenylsilyly)benzene layer doped with 25wt% FIr6 were employed to maximize exciton generation on FIr6 molecules. Combined with the p-i-n device structure, we achieved a low turn-on voltage of 3.2V and very high power efficiencies of 25±2lm∕W at 100cd∕m2 and 20±2lm∕W at 1000cd∕m2 for such deep-blue PHOLEDs with peak emission at a wavelength of 458nm. DA - 2008/9/29/ PY - 2008/9/29/ DO - 10.1063/1.2996274 VL - 93 IS - 13 SP - 133309 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2996274 DB - Crossref ER - TY - JOUR TI - Effects of triplet energies and transporting properties of carrier transporting materials on blue phosphorescent organic light emitting devices AU - Lee, Jaewon AU - Chopra, Neetu AU - Eom, Sang-Hyun AU - Zheng, Ying AU - Xue, Jiangeng AU - So, Franky AU - Shi, Jianmin T2 - Applied Physics Letters AB - We have studied the effects of the hole transporting layers and electron transporting layers on the device efficiencies of iridium(III) bis[(4,6-di-fluorophenyl)-pyridinato-N,C2′] picolinate (FIrpic) doped 3,5′−N,N′-dicarbazole-benzene (mCP) host blue phosphorescent organic light emitting diodes. We found that the device efficiency is very sensitive to the hole transporting materials used and both the triplet energy and carrier transport properties affect the device efficiency. On the other hand, there is no apparent correlation between the device efficiency and the triplet energy of the electron transporting material used. Instead, the device efficiency is affected by the electron mobility of the electron transporting layer only. DA - 2008/9/22/ PY - 2008/9/22/ DO - 10.1063/1.2978235 VL - 93 IS - 12 SP - 123306 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2978235 DB - Crossref ER - TY - JOUR TI - Organic/inorganic nanocomposites for high-dielectric-constant materials AU - Sarasqueta, Galileo AU - Roy Choudhury, Kaushik AU - Kim, Do Young AU - So, Franky T2 - Applied Physics Letters AB - A different approach to fabricate metallic nanostructures in an insulating organic matrix in situ using thermal coevaporation is demonstrated. The method is used to fabricate metal-organic percolative nanocomposite capacitors. Thermal annealing of the nanocomposite films results in a dramatic enhancement (&gt;50 times at 10kHz) of the dielectric constant accompanied by significant lowering (approximately four times) of conductivity and dissipation loss, especially at low frequencies. The improved performance is attributed to structural modifications in the films resulting from enhanced phase segregation of constituents, induced by annealing at optimized temperatures. DA - 2008/9/22/ PY - 2008/9/22/ DO - 10.1063/1.2963193 VL - 93 IS - 12 SP - 123305 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2963193 DB - Crossref ER - TY - JOUR TI - Efficient deep-blue phosphorescent organic light-emitting device with improved electron and exciton confinement AU - Zheng, Ying AU - Eom, Sang-Hyun AU - Chopra, Neetu AU - Lee, Jaewon AU - So, Franky AU - Xue, Jiangeng T2 - Applied Physics Letters AB - We report a significant improvement in the efficiency of deep-blue phosphorescent organic light-emitting devices based on the electrophosphorescent dye bis(4′,6′-difluorophenylpyridinato)tetrakis (1-pyrazolyl) borate (FIr6). Using 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) as the hole transport layer (HTL), we achieved a maximum external quantum efficiency of ηEQE=(18±1)%, which is approximately 50% higher than ηEQE=12% in a previously reported device with bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl as the HTL. The maximum luminous power efficiency was also improved from (14±1)lm∕W to (18±1)lm∕W. We attribute this efficiency improvement to the enhanced electron and exciton confinement provided by TAPC. DA - 2008/6/2/ PY - 2008/6/2/ DO - 10.1063/1.2937403 VL - 92 IS - 22 SP - 223301 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2937403 DB - Crossref ER - TY - JOUR TI - Cavity effects on light extraction in organic light emitting devices AU - Lee, Jaewon AU - Chopra, Neetu AU - So, Franky T2 - Applied Physics Letters AB - We have demonstrated that the light extraction efficiency of an organic light emitting device is a strong function of device geometry. Specifically, we have found that the ratio of the extracted mode to the substrate-guided mode varies from 22% to 55% depending on the location of the recombination zone. Our simulation results also indicate that more light is trapped in the substrate as the optical length of device increases. We further show that the light intensity profile varies from a Lambertian shape to a non-Lambertian shape depending on the device geometry due to the cavity effect. DA - 2008/1/21/ PY - 2008/1/21/ DO - 10.1063/1.2830820 VL - 92 IS - 3 SP - 033303 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2830820 DB - Crossref ER - TY - JOUR TI - Effects of solution-processed polymer interlayers on hole injection and device performance of polymer light-emitting diodes AU - Harding, M. James AU - Poplavskyy, Dmitry AU - Choong, V.-E. AU - Campbell, Alasdair J. AU - So, Franky T2 - Organic Electronics AB - We present studies of current density and photometric efficiency using three well known, commercially available polyphenylenevinylene and polyfluorene based light-emitting polymers (LEPs) with different interlayers. The thin, spin-coated interlayers of poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB) and poly[9,9-dioctyl-fluorene-co-(bis-N,N′-(3-carboxyphenyl)-bis-N,N′-phenylbenzidine)] (BFA) are placed between the poly(3,4-ethylenedioxythiophene)/polystyrenesulphonic acid (PEDOT:PSS) anode and the LEP. It is found that despite having very similar HOMO levels (±0.1 eV) to the LEPs, the interlayers alter both the hole injection efficiency and the photometric efficiency of PLED devices. The increase or decrease of these depends on the particular interlayer-LEP combination involved, but there is a strong, general correlation between poorer hole injection resulting in a higher photometric efficiency. We attribute the variation in hole injection to the altered morphology and contact area at the anode interfaces, with the possible involvement of mobility-dependant space-charge effects or charge trapping. The dominant process in improving the photometric efficiency must be better electron-hole current balance, and/or the shift of the recombination zone to a more favourable position with less exciton quenching. The interlayers do not act as electron blocking layers, but hole injection enhancement by electron injection does seem to occur. These results show that interlayers can both increase and decrease device performance, depending on the interlayer-LEP combination involved. DA - 2008/4// PY - 2008/4// DO - 10.1016/j.orgel.2007.09.003 VL - 9 IS - 2 SP - 183-190 J2 - Organic Electronics LA - en OP - SN - 1566-1199 UR - http://dx.doi.org/10.1016/j.orgel.2007.09.003 DB - Crossref KW - polymer KW - light-emitting diode KW - interlayer KW - injection ER - TY - JOUR TI - Carbon-Nanotube-Enabled Vertical Field Effect and Light-Emitting Transistors AU - Liu, Bo AU - McCarthy, Mitchell A. AU - Yoon, Youngki AU - Kim, Do Young AU - Wu, Zhuangchun AU - So, Franky AU - Holloway, Paul H. AU - Reynolds, John R. AU - Guo, Jing AU - Rinzler, Andrew G. T2 - Advanced Materials AB - In contrast to typical metals, carbon nanotubes are shown to form a unique Schottky barrier contact with semiconductors wherein a gate field can modulate not only the band bending in the semiconductor but also the height of the barrier. These phenomena are exploited to enable two new device architectures: a vertical field-effect transistor (figure) and a vertical light-emitting transistor. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2089/2008/adma200800601_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2008/10/2/ PY - 2008/10/2/ DO - 10.1002/adma.200800601 VL - 20 IS - 19 SP - 3605-3609 J2 - Adv. Mater. LA - en OP - SN - 0935-9648 1521-4095 UR - http://dx.doi.org/10.1002/adma.200800601 DB - Crossref ER - TY - JOUR TI - LiF as an n-Dopant in Tris(8-hydroxyquinoline) Aluminum Thin Films AU - Choudhury, Kaushik Roy AU - Yoon, Jong-hyuk AU - So, Franky T2 - Advanced Materials AB - Facile non-alkaline n-doping of Alq3with LiF is achieved by co-evaporation. Optimal doping not only leads to enhanced device currents and conductivity, but also changes the very nature of carrier injection and transport. Using this scheme, efficient electron injection is achieved without using low-work-function cathodes. A doped transport layer (see figure) inOL EDs leads to balanced injection andtransport of charge carriers and resultsin excellent device performance. DA - 2008/4/21/ PY - 2008/4/21/ DO - 10.1002/adma.200701657 VL - 20 IS - 8 SP - 1456-1461 J2 - Adv. Mater. LA - en OP - SN - 0935-9648 1521-4095 UR - http://dx.doi.org/10.1002/adma.200701657 DB - Crossref ER - TY - JOUR TI - Microstructural and Interface Analysis of Ceramic Eutectic Composites AU - Dickey, EC AU - Philips, C AU - Polotai, AV T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/S1431927608088119 VL - 14 IS - S2 SP - 142-143 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927608088119 DB - Crossref ER - TY - JOUR TI - Microstructural and Radial Distribution Function Analysis of Hydrogenated Silicon, Germanium, and Silicon-Germanium Alloy Thin Films AU - John, DB Saint AU - Podraza, NJ AU - Gauntt, BD AU - Li, J AU - Dickey, EC T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/S1431927608087631 VL - 14 IS - S2 SP - 406-407 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927608087631 DB - Crossref ER - TY - JOUR TI - TEM Characterization of Microtwins in VOx thin films AU - Li, J AU - Gauntt, BD AU - Dickey, EC T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/S1431927608086790 VL - 14 IS - S2 SP - 226-227 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927608086790 DB - Crossref ER - TY - JOUR TI - Disordered Vanadium Oxide Thin Films for Use in Infrared Detection AU - Gauntt, BD AU - Li, J AU - Kulik, J AU - Dickey, EC T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/S1431927608086650 VL - 14 IS - S2 SP - 236-237 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927608086650 DB - Crossref ER - TY - JOUR TI - TEM Characterization of Nanometer-Scale Spinel /Rocksalt Phase Decomposition in Nickel Magnanite Thin Film AU - Li, J AU - Schulze, H AU - Bharadwaja, SSN AU - Dickey, EC AU - Trolier-McKinstry, S T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/S1431927608086170 VL - 14 IS - S2 SP - 228-229 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927608086170 DB - Crossref ER - TY - JOUR TI - EDX Analysis of Grain Boundary Segregation in 1 at% Nd Doped Polycrystalline YAG AU - Li, X AU - Stevenson, A AU - Messing, G AU - Dickey, EC T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/S1431927608084134 VL - 14 IS - S2 SP - 1420-1421 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927608084134 DB - Crossref ER - TY - JOUR TI - Anodic Tantalum Pentoxide: Chemical and Structural Characterization of a Bi-Layer Oxide AU - Sloppy, J Ray AU - Li, J AU - Dickey, EC T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/S143192760808392X VL - 14 IS - S2 SP - 328-329 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S143192760808392X DB - Crossref ER - TY - JOUR TI - Site-Specific Studies of Electrical Heterogeneities in Ni-BaTiO3 Multilayer Ceramic Capacitors Using FIB and AEM AU - Yang, GY AU - Moses, PJ AU - Dickey, EC AU - Randall, CA T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/S1431927608082895 VL - 14 IS - S2 SP - 992-993 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927608082895 DB - Crossref ER - TY - JOUR TI - Atomic Investigation of Al2O3/GaN Heterostructures Interfaces using Aberration-Corrected STEM Combined with First-Principles Methods AU - Idrobo, JC AU - Pant, P AU - Narayan, J AU - Pennycook, SJ AU - Pantelides, ST T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/S1431927608087187 VL - 14 IS - S2 SP - 1402-1403 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927608087187 DB - Crossref ER - TY - JOUR TI - Investigation of heteroepitaxy on nanoscopically roughened (001)Si by real-time spectroscopic polarimetry AU - Liu, X. AU - Kim, I.-K. AU - Aspnes, D. E. T2 - physica status solidi (c) AB - We use a real-time spectroscopic polarimeter integrated with an organometallic chemical vapor deposition system to investigate growth of GaP on Si, and particularly nanoscopically roughened (nr-)Si. We find nanoroughening is necessary to increase the density of nucleation sites and decrease reactant mobility and thereby grow continuous films instead of widely spaced islands. The nrSi surfaces are more highly reactive to the trimethylgallium precursor than III-V growth surfaces, leading to the appearance of metallic Ga if standard growth conditions are used in the initial phase of heteroepitaxy. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2008/5// PY - 2008/5// DO - 10.1002/pssc.200777896 VL - 5 IS - 5 SP - 1312-1315 J2 - phys. stat. sol. (c) LA - en OP - SN - 1610-1634 1610-1642 UR - http://dx.doi.org/10.1002/pssc.200777896 DB - Crossref ER - TY - JOUR TI - Single-electron transistors made by chemical patterning of silicon dioxide substrates and selective deposition of gold nanoparticles AU - Coskun, Ulas C. AU - Mebrahtu, Henok AU - Huang, Paul B. AU - Huang, Jeremy AU - Sebba, David AU - Biasco, Adriana AU - Makarovski, Alex AU - Lazarides, Anne AU - LaBean, Thom H. AU - Finkelstein, Gleb T2 - Applied Physics Letters AB - We describe a method to pattern SiO2 surfaces with colloidal gold nanoparticles by e-beam lithography and selective nanoparticle deposition. The simple technique allows us to deposit nanoparticles in continuous straight lines, just one nanoparticle wide and many nanoparticles long. We contact the prepositioned nanoparticles with metal leads to form single electron transistors. The Coulomb blockade pattern surprisingly does not show the parasitic “offset charges” at low temperatures, indicating relatively little surface contamination. DA - 2008/9/22/ PY - 2008/9/22/ DO - 10.1063/1.2981705 VL - 93 IS - 12 SP - 123101 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2981705 DB - Crossref ER - TY - JOUR TI - A DNA Nanotransport Device Powered by Polymerase ϕ29 AU - Sahu, Sudheer AU - LaBean, Thomas H. AU - Reif, John H. T2 - Nano Letters AB - Polymerases are a family of enzymes responsible for copying or replication of nucleic acids (DNA or RNA) templates and hence sustenance of life processes. In this paper, we present a method to exploit a strand-displacing polymerase phi29 as a driving force for nanoscale transportation devices. The principal idea behind the device is strong strand displacement ability of phi29, which can displace any DNA strand from its template while extending a primer hybridized to the template. This capability of phi29 is used to power the movement of a target nanostructure on a DNA track. The major advantage of using a polymerase driven nanotransportation device as compared to other existing nanorobotical devices is its speed. phi29 polymerase can travel at the rate of 2000 nucleotides per minute at room temperature, which translates to approximately 680 nm min(-1) on a nanostructure. We also demonstrate transportation of a DNA cargo on a DNA track with the help of fluorescence resonance electron transfer data. DA - 2008/11/12/ PY - 2008/11/12/ DO - 10.1021/nl802294d VL - 8 IS - 11 SP - 3870-3878 J2 - Nano Lett. LA - en OP - SN - 1530-6984 1530-6992 UR - http://dx.doi.org/10.1021/nl802294d DB - Crossref ER - TY - JOUR TI - Reconfigurable Core−Satellite Nanoassemblies as Molecularly-Driven Plasmonic Switches AU - Sebba, David S. AU - Mock, Jack J. AU - Smith, David R. AU - LaBean, Thomas H. AU - Lazarides, Anne A. T2 - Nano Letters AB - Molecular control of plasmon coupling is investigated in sub-100 nm assemblies composed of 13 nm gold "satellite" particles tethered by reconfigurable DNA nanostructures to a 50 nm gold "core" particle. Reconfiguration of the DNA nanostructures from a compact to an extended state results in blue shifting of the assembly plasmon resonance, indicating reduced interparticle coupling and lengthening of the core-satellite tether. Scattering spectra of the core-satellite assemblies before and after reconfiguration are compared with spectra calculated using a structural model that incorporates the core/satellite ratio determined by TEM imaging and estimates of tether length based upon prior measurements of interparticle separation in DNA linked nanoparticle networks. A strong correspondence between measured and simulated difference spectra validates the structural models that link the observed plasmon modulation with DNA nanostructure reconfiguration. DA - 2008/7// PY - 2008/7// DO - 10.1021/nl080029h VL - 8 IS - 7 SP - 1803-1808 J2 - Nano Lett. LA - en OP - SN - 1530-6984 1530-6992 UR - http://dx.doi.org/10.1021/nl080029h DB - Crossref ER - TY - JOUR TI - Stepwise Self-Assembly of DNA Tile Lattices Using dsDNA Bridges AU - Park, Sung Ha AU - Finkelstein, Gleb AU - LaBean, Thomas H. T2 - Journal of the American Chemical Society AB - The simple helical motif of double-strand DNA (dsDNA) has typically been judged to be uninteresting for assembly in DNA-based nanotechnology applications. In this letter, we demonstrate construction of superstructures consisting of heterogeneous DNA motifs using dsDNA in conjunction with more complex, cross-tile building blocks. Incorporation of dsDNA bridges in stepwise assembly processes can be used for controlling length and directionality of superstructures and is analogous to the "reprogramming" of sticky-ends displayed on the DNA tiles. Two distinct self-assembled DNA lattices, fixed-size nanoarrays, and extended 2D crystals of nanotracks with nanobridges, are constructed and visualized by high-resolution, liquid-phase atomic force microscopy. DA - 2008/1// PY - 2008/1// DO - 10.1021/ja078122f VL - 130 IS - 1 SP - 40-41 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja078122f DB - Crossref ER - TY - JOUR TI - Plasmon coupling in binary metal core–satellite assemblies AU - Sebba, D. S. AU - LaBean, T. H. AU - Lazarides, A. A. T2 - Applied Physics B DA - 2008/9/13/ PY - 2008/9/13/ DO - 10.1007/s00340-008-3212-2 VL - 93 IS - 1 SP - 69-78 J2 - Appl. Phys. B LA - en OP - SN - 0946-2171 1432-0649 UR - http://dx.doi.org/10.1007/s00340-008-3212-2 DB - Crossref ER - TY - CHAP TI - Activatable Tiles: Compact, Robust Programmable Assembly and Other Applications AU - Majumder, Urmi AU - LaBean, Thomas H. AU - Reif, John H. T2 - DNA Computing AB - While algorithmic DNA self-assembly is, in theory, capable of forming complex patterns, its experimental demonstration has been limited by significant assembly errors. In this paper we describe a novel protection/deprotection strategy to strictly enforce the direction of tiling assembly growth to ensure the robustness of the assembly process. Tiles are initially inactive, meaning that each tile’s output pads are protected and cannot bind with other tiles. After other tiles bind to the tile’s input pads, the tile transitions to an active state and its output pads are exposed, allowing further growth. We prove that an activatable tile set is an instance of a compact, error-resilient and self-healing tile-set. We also describe a DNA design for activatable tiles and a deprotection mechanism using DNA polymerase enzymes and strand displacement. We conclude with a discussion on some applications of activatable tiles beyond computational tiling. PY - 2008/2/8/ DO - 10.1007/978-3-540-77962-9_2 SP - 15-25 OP - PB - Springer Berlin Heidelberg SN - 9783540779612 9783540779629 UR - http://dx.doi.org/10.1007/978-3-540-77962-9_2 DB - Crossref ER - TY - JOUR TI - Heterostructured DNA templates: A combined magnetic force microscopy and circular dichroism study AU - Jaganathan, Hamsa AU - Ivanisevic, Albena T2 - Applied Physics Letters AB - The effect of nanoparticle (NP) concentration was examined on the formation of heterostructured nanowires fabricated using DNA as a template. At mass ratios of 1:1 DNA:NP, the circular dichroism (CD) data showed a distinct characteristic, a plateau at 260 nm. The magnetic force microscopy (MFM) data revealed segments that showed variable interaction with the magnetized tip. At high NP concentrations both the CD and MFM data confirmed that the DNA template denatures and the control over the assembly process is poor. DA - 2008/12/29/ PY - 2008/12/29/ DO - 10.1063/1.3058711 VL - 93 IS - 26 SP - 263104 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3058711 DB - Crossref KW - biological techniques KW - biomagnetism KW - bio-optics KW - dichroism KW - DNA KW - magnetic force microscopy KW - molecular biophysics KW - nanobiotechnology KW - nanoparticles KW - nanowires ER - TY - JOUR TI - Electrical detection of the biological interaction of a charged peptide via gallium arsenide junction-field-effect transistors AU - Lee, Kangho AU - Nair, Pradeep R. AU - Alam, Muhammad A. AU - Janes, David B. AU - Wampler, Heeyeon P. AU - Zemlyanov, Dmitry Y. AU - Ivanisevic, Albena T2 - Journal of Applied Physics AB - GaAs junction-field-effect transistors (JFETs) are utilized to achieve label-free detection of biological interaction between a probe transactivating transcriptional activator (TAT) peptide and the target trans-activation-responsive (TAR) RNA. The TAT peptide is a short sequence derived from the human immunodeficiency virus-type 1 TAT protein. The GaAs JFETs are modified with a mixed adlayer of 1-octadecanethiol (ODT) and TAT peptide, with the ODT passivating the GaAs surface from polar ions in physiological solutions and the TAT peptide providing selective binding sites for TAR RNA. The devices modified with the mixed adlayer exhibit a negative pinch-off voltage (VP) shift, which is attributed to the fixed positive charges from the arginine-rich regions in the TAT peptide. Immersing the modified devices into a TAR RNA solution results in a large positive VP shift (&gt;1 V) and a steeper subthreshold slope (∼80 mV/decade), whereas “dummy” RNA induced a small positive VP shift (∼0.3 V) without a significant change in subthreshold slopes (∼330 mV/decade). The observed modulation of device characteristics is analyzed with analytical modeling and two-dimensional numerical device simulations to investigate the electronic interactions between the GaAs JFETs and biological molecules. DA - 2008/6// PY - 2008/6// DO - 10.1063/1.2936853 VL - 103 IS - 11 SP - 114510 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.2936853 DB - Crossref ER - TY - JOUR TI - Collagen-Binding Peptide Interaction with Retinal Tissue Surfaces AU - Sistiabudi, Rizaldi AU - Ivanisevic, Albena T2 - Langmuir AB - One of the current challenges in treating age-related macular degeneration (AMD) is the surface modification of the retinal Bruch membrane. In this study, the collagen fibers of the inner collagenous zone of the Bruch membrane were identified as type I and type III. Subsequently, the adsorption of a collagen-binding peptide onto the inner collagenous zone surface was investigated. The collagen-binding peptide was able to bind specifically to the collagen fibers while maintaining the biological activity of the N-terminus biotin tag. These results indicate that the collagen-binding peptide may be used as an anchor to immobilize bioactive molecules on the inner collagenous zone surface of the Bruch membrane. DA - 2008/3// PY - 2008/3// DO - 10.1021/la703561d VL - 24 IS - 5 SP - 1591-1594 J2 - Langmuir LA - en OP - SN - 0743-7463 1520-5827 UR - http://dx.doi.org/10.1021/la703561d DB - Crossref ER - TY - JOUR TI - Mixed Adlayer of Alkanethiol and Peptide on GaAs(100):  Quantitative Characterization by X-ray Photoelectron Spectroscopy AU - Wampler, Heeyeon P. AU - Zemlyanov, Dmitry Y. AU - Lee, Kangho AU - Janes, David B. AU - Ivanisevic, Albena T2 - Langmuir AB - Homogeneous and mixed adlayers composed of an alkanethiol (1-octadecanethiol, ODT) and a peptide (CGISYGRKKRRQRRR) on GaAs(100) were formed in two different solvent systems: phosphate-buffered saline (PBS) and N,N-dimethylformamide (DMF). The chemical composition of each adlayer was characterized by X-ray photoelectron spectroscopy (XPS). The data showed that the makeup of the adlayer and its stability largely depends on the solvent used. Angle-resolved XPS also revealed that the adlayer thickness and tilt angles were different from values obtained from ellipsometry measurements and vastly varied between the two solvents used. The coverage data extracted from the XPS measurements indicated that homogeneous adlayers of peptide in PBS buffer form a multilayered film. Homogeneous alkanethiol adlayers exhibited monolayer coverage under all solvent treatments. Coadsorbed layers containing both alkanethiol and peptide have fractional monolayer coverage in both solvents. DA - 2008/4// PY - 2008/4// DO - 10.1021/la703543g VL - 24 IS - 7 SP - 3164-3170 J2 - Langmuir LA - en OP - SN - 0743-7463 1520-5827 UR - http://dx.doi.org/10.1021/la703543g DB - Crossref ER - TY - JOUR TI - Quantitative Evaluation of Covalently Bound Molecules on GaP (100) Surfaces AU - Flores-Perez, Rosangelly AU - Zemlyanov, Dmitry Y. AU - Ivanisevic, Albena T2 - The Journal of Physical Chemistry C AB - The study utilizes surface sensitive techniques in order to quantitatively characterize the nature of organization and bonding of alkanethiol adsorbates on GaP (100) surfaces. The evaluation was performed using water contact angle, atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The hydrophobicity and consistency of surface roughness were studied via water contact angle and AFM. The FT-IR experimental protocol permitted the identification of characteristic functional groups on the surface and enabled insight into the organization within the adlayers on the GaP surface. XPS data showed evidence for the formation of a covalent bond between the sulfur and the surface and was used to calculate the adlayer thicknesses, tilt angles, and molecular coverages for different adsorbates. The thickness and tilt angles values were comparable to other modified semiconductor materials. High coverages were observed for all alkanethiols on GaP (100). The quantitative XPS protocol reported can be applied to the evaluation of other adsorbates on semiconductor materials. DA - 2008/2// PY - 2008/2// DO - 10.1021/jp710437v VL - 112 IS - 6 SP - 2147-2155 J2 - J. Phys. Chem. C LA - en OP - SN - 1932-7447 1932-7455 UR - http://dx.doi.org/10.1021/jp710437v DB - Crossref ER - TY - JOUR TI - Lithography on GaP(100) surfaces AU - Flores-Perez, Rosangelly AU - Zemlyanov, Dmitry Y. AU - Ivanisevic, Albena T2 - Surface Science AB - Abstract Two types of lithographic methods were used to modify GaP(1 0 0) surfaces with commercially available alkanethiol molecules: microcontact printing (μCP) and “dip-pen” nanolithography (DPN). The patterned surfaces were characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS). The characterization was done in order to understand the quality of each type of pattern, its chemical composition, and the organization of the molecules on the surface. Differences between the two lithographic methods used to do lithography on the GaP(1 0 0) in this study were dependent on the chosen molecular “ink”. DA - 2008/6// PY - 2008/6// DO - 10.1016/j.susc.2008.04.002 VL - 602 IS - 11 SP - 1993-1998 J2 - Surface Science LA - en OP - SN - 0039-6028 UR - http://dx.doi.org/10.1016/j.susc.2008.04.002 DB - Crossref KW - gallium phosphide KW - atomic force microscopy KW - X-ray photoelectron spectroscopy KW - infrared spectroscopy KW - microcontact printing (mu CP) KW - dip-pen nanolithography (DPN) ER - TY - JOUR TI - Circular dichroism study of enzymatic manipulation on magnetic and metallic DNA template nanowires AU - Jaganathan, Hamsa AU - Ivanisevic, Albena T2 - Colloids and Surfaces B: Biointerfaces AB - Circular dichroism spectroscopy (CD) was used to examine the mechanism of endonuclease clipping and ligation of the DNA template nanowires. The biomolecular manipulation of the DNA template is compared for both metallic (Au) and magnetic (Fe2O3 and CoFe2O4) nanowires. The dependence of nanoparticle (NP) concentration on enzymatic clipping and DNA ligation was studied, in addition to performing absorbance and thermal melting experiments. Low-NP concentration preserved and digested the DNA template structure. Yet, at higher NP concentrations, the DNA template began to denature before enzyme addition. It was also observed that ligation of the digested DNA occurred more efficiently at low-NP concentrations. These results provide significant information on structural alteration and biorecognition effectiveness of the DNA template after enzymatic manipulation. DA - 2008/12// PY - 2008/12// DO - 10.1016/j.colsurfb.2008.08.024 VL - 67 IS - 2 SP - 279-283 J2 - Colloids and Surfaces B: Biointerfaces LA - en OP - SN - 0927-7765 UR - http://dx.doi.org/10.1016/j.colsurfb.2008.08.024 DB - Crossref KW - DNA templates KW - Ligation KW - Restriction enzymes KW - Circular dichroism KW - Nanoparticles ER - TY - JOUR TI - Fabrication of ordered metallic and magnetic heterostructured DNA—Nanoparticle hybrids AU - Kinsella, Joseph M. AU - Ivanisevic, Albena T2 - Colloids and Surfaces B: Biointerfaces AB - Here we provide a method based on enzymatically catalyzed reactions to cleave and ligate DNA molecules coated with nanoparticles to fabricate multi-component structures. This is done by simultaneously digesting two solutions of nanoparticle coated DNA, one with iron oxide particles the other gold particles, which yields short DNA fragments with complementary single stranded overhangs. When added together and re-attached using ligase enzymes multi-component nanoparticle coated structures are formed providing a novel method to fabricate complicated nanoparticle arrangements from the bottom up. We evaluated the fabrication by characterizing the samples with gel electrophoresis and magnetic force microscopy (MFM). The electrophoresis provides proof that the coated DNA molecules were digested with restriction enzymes and ligated by the T4 ligase enzymes. MFM experiments allow us to visualize the multi-component strands and analyze the magnetic versus metallic segments. DA - 2008/6// PY - 2008/6// DO - 10.1016/j.colsurfb.2007.12.004 VL - 63 IS - 2 SP - 296-300 J2 - Colloids and Surfaces B: Biointerfaces LA - en OP - SN - 0927-7765 UR - http://dx.doi.org/10.1016/j.colsurfb.2007.12.004 DB - Crossref KW - hybrid materials KW - data storage KW - magnetic nanoparticles KW - scanning probe microscopy ER - TY - JOUR TI - Repairing the Damaged Spinal Cord and Brain with Nanomedicine AU - Cho, Youngnam AU - Shi, Riyi AU - Borgens, Richard AU - Ivanisevic, Albena T2 - Small AB - Polyethylene glycol (PEG)-coated silica colloids circulating in the bloodstream target only injured tissues, particularly a spinal-cord injury (see picture). The PEG coating both seals and induces repair of damaged cells, leading to a recovery of physiological function. These PEG-coated colloids have been characterized, tested in ex vivo spinal cord and in living adult Guinea pig spinal-cord injury. DA - 2008/10// PY - 2008/10// DO - 10.1002/smll.200800838 VL - 4 IS - 10 SP - 1676-1681 J2 - Small LA - en OP - SN - 1613-6810 1613-6829 UR - http://dx.doi.org/10.1002/smll.200800838 DB - Crossref ER - TY - JOUR TI - Circular Dichroism Study of the Mechanism of Formation of DNA Templated Nanowires AU - Jaganathan, Hamsa AU - Kinsella, Joseph M. AU - Ivanisevic, Albena T2 - ChemPhysChem AB - Abstract In order to control the fabrication method, the mechanism used in the formation of DNA templated nanowires is investigated through circular dichroism (CD) spectroscopy. Metallic (Au) and magnetic (Fe 2 O 3 and CoFe 2 O 4 ) nanoparticles (NP) are aligned along the DNA strand at various mass ratios. The DNA templated nanowires are compared to the structure of B‐form dsDNA through CD experiments. Absorbance and thermal melting tests are performed to verify the structural changes of DNA templated nanowires. Low concentrations of nanoparticles preserve the DNA B‐form through electrostatic interactions. Conversely, at higher concentrations of nanoparticles aligned along the DNA strand, the template is denatured. Information on the mode of nanoparticle binding and DNA helix alterations are explored for metallic and magnetic nanowires based upon the results. DA - 2008/10/24/ PY - 2008/10/24/ DO - 10.1002/cphc.200800509 VL - 9 IS - 15 SP - 2203-2206 J2 - ChemPhysChem LA - en OP - SN - 1439-4235 1439-7641 UR - http://dx.doi.org/10.1002/cphc.200800509 DB - Crossref KW - circular dichroism KW - DNA KW - nanoparticles KW - templates ER - TY - JOUR TI - DNA Molecules on GaP (100) Surfaces: Spectroscopic Characterization and Biospecificity Assessment AU - Flores-Perez, Rosangelly AU - Zemlyanov, Dmitry Y. AU - Ivanisevic, Albena T2 - ChemPhysChem AB - Mind the bioactive GaP: Carboxylic acid-terminated GaP(100) surfaces are used to capture DNA molecules. The well-packed mixed biotin-modified DNA and alkyl-chains self-assemble onto the substrate (see figure) and exhibit good reproducibility, specificity and bioactivity confirmed by the use of nanoparticles and Cy3 fluorophore conjugates with streptavidin. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2267/2008/z800166_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2008/8/4/ PY - 2008/8/4/ DO - 10.1002/cphc.200800166 VL - 9 IS - 11 SP - 1528-1530 J2 - ChemPhysChem LA - en OP - SN - 1439-4235 1439-7641 UR - http://dx.doi.org/10.1002/cphc.200800166 DB - Crossref KW - atomic force microscopy KW - biosensors KW - DNA KW - gallium phosphide KW - surface chemistry ER - TY - JOUR TI - Dip-Pen Nanolithography of Bioactive Peptides on Collagen-Terminated Retinal Membrane AU - Sistiabudi, Rizaldi AU - Ivanisevic, Albena T2 - Advanced Materials AB - Dip-pen nanolithography is used to directly modify freshly dissected eye tissues with biologically active collagen-binding peptide molecules. The results address the challenge of surface heterogeneity and utilize dip-pen nanolithography to control the localization and concentration of molecules on a collagen-terminated tissue-derived surface. This method can allow the development of scaffolds for treatment of age-related macular degeneration. DA - 2008/10/2/ PY - 2008/10/2/ DO - 10.1002/adma.200800950 VL - 20 IS - 19 SP - 3678-3681 J2 - Adv. Mater. LA - en OP - SN - 0935-9648 1521-4095 UR - http://dx.doi.org/10.1002/adma.200800950 DB - Crossref ER - TY - JOUR TI - Atomic structure of postgrowth annealed epitaxial Fe/(001)GaAs interfaces AU - LeBeau, James M. AU - Hu, Qi O. AU - Palmstrøm, Christopher J. AU - Stemmer, Susanne T2 - Applied Physics Letters AB - The interfacial atomic structure of epitaxial Fe films grown by molecular beam epitaxy on c(4×4) reconstructed (001) GaAs was investigated using high-angle annular dark-field imaging in scanning transmission electron microscopy. No extended interfacial reaction phase is observed and the image contrast is discussed in terms of the interface atomic configuration. The images show an As-terminated semiconductor. The interface consists of a single partially occupied plane inserted between the Fe film and the GaAs, which most likely is occupied by Fe. This interface structure provides strong evidence for preferential Fe–As bonding across the interface. DA - 2008/9/22/ PY - 2008/9/22/ DO - 10.1063/1.2990622 VL - 93 IS - 12 SP - 121909 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2990622 DB - Crossref ER - TY - JOUR TI - Near-infrared absorption and semimetal-semiconductor transition in 2nm ErAs nanoparticles embedded in GaAs and AlAs AU - Scarpulla, Michael A. AU - Zide, Joshua M. O. AU - LeBeau, James M. AU - Van de Walle, Chris G. AU - Gossard, Arthur C. AU - Delaney, Kris T. T2 - Applied Physics Letters AB - We report strong near-infrared absorption peaks in epitaxial films of GaAs and AlAs containing approximately 0.5–5% of the semimetal ErAs. The energy of the resonant absorption peak can be changed from 0.62to1.0eV (2.2–1.4μm) by variation of the ErAs volume fraction and the substrate temperature. We interpret the infrared absorption in terms of transitions across an energy gap caused by a confinement-induced semimetal-semiconductor transition. An effective mass model relates the changes in nanoparticle diameter observed in transmission electron microscopy to the energy gap. DA - 2008/4/28/ PY - 2008/4/28/ DO - 10.1063/1.2908213 VL - 92 IS - 17 SP - 173116 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2908213 DB - Crossref ER - TY - JOUR TI - Quantitative HAADF-STEM and EELS AU - LeBeau, JM AU - Findlay, SD AU - Allen, LJ AU - Stemmer, S T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/S1431927608082263 VL - 14 IS - S2 SP - 1352-1353 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927608082263 DB - Crossref ER - TY - JOUR TI - Simulation of Atomic Resolution Images in STEM AU - Allen, LJ AU - D'Alfonso, AJ AU - Bosman, M AU - Findlay, SD AU - Oxley, MP AU - Keast, VJ AU - LeBeau, JM AU - Stemmer, S T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/S1431927608082019 VL - 14 IS - S2 SP - 922-923 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927608082019 DB - Crossref ER - TY - JOUR TI - Experimental quantification of annular dark-field images in scanning transmission electron microscopy AU - LeBeau, James M. AU - Stemmer, Susanne T2 - Ultramicroscopy AB - This paper reports on a method to obtain atomic resolution Z-contrast (high-angle annular dark-field) images with intensities normalized to the incident beam. The procedure bypasses the built-in signal processing hardware of the microscope to obtain the large dynamic range necessary for consecutive measurements of the incident beam and the intensities in the Z-contrast image. The method is also used to characterize the response of the annular dark-field detector output, including conditions that avoid saturation and result in a linear relationship between the electron flux reaching the detector and its output. We also characterize the uniformity of the detector response across its entire area and determine its size and shape, which are needed as input for image simulations. We present normalized intensity images of a SrTiO3 single crystal as a function of thickness. Averaged, normalized atom column intensities and the background intensity are extracted from these images. The results from the approach developed here can be used for direct, quantitative comparisons with image simulations without any need for scaling. DA - 2008/11// PY - 2008/11// DO - 10.1016/j.ultramic.2008.07.001 VL - 108 IS - 12 SP - 1653-1658 J2 - Ultramicroscopy LA - en OP - SN - 0304-3991 UR - http://dx.doi.org/10.1016/j.ultramic.2008.07.001 DB - Crossref KW - Z-contrast KW - HAADF KW - STEM ER - TY - JOUR TI - Excitation of Local Field Enhancement on Silicon Nanowires AU - Cao, Linyou AU - Garipcan, Bora AU - Gallo, Eric M. AU - Nonnenmann, Stephen S. AU - Nabet, Bahram AU - Spanier, Jonathan E. T2 - Nano Letters AB - The interaction between light and reduced-dimensionality silicon attracts significant interest due to the possibilities of designing nanoscaled optical devices, highly cost-efficient solar cells, and ultracompact optoelectronic systems that are integrated with standard microelectronic technology. We demonstrate that Si nanowires (SiNWs) possessing metal-nanocluster coatings support a multiplicatively enhanced near-field light-matter interaction. Raman scattering from chemisorbed probing molecules provides a quantitative measure of the strength of this enhanced coupling. An enhancement factor of 2 orders of magnitude larger than that for the surface plasmon resonance alone (without the SiNWs) along with the attractive properties of SiNWs, including synthetic controllability of shape, indicates that these nanostructures may be an attractive and versatile material platform for the design of nanoscaled optical and optoelectronic circuits. DA - 2008/2// PY - 2008/2// DO - 10.1021/nl0729983 VL - 8 IS - 2 SP - 601-605 J2 - Nano Lett. LA - en OP - SN - 1530-6984 1530-6992 UR - http://dx.doi.org/10.1021/nl0729983 DB - Crossref ER - TY - JOUR TI - Evidence for two distinct scales of current flow in polycrystalline Sm and Nd iron oxypnictides AU - Yamamoto, A AU - Polyanskii, A A AU - Jiang, J AU - Kametani, F AU - Tarantini, C AU - Hunte, F AU - Jaroszynski, J AU - Hellstrom, E E AU - Lee, P J AU - Gurevich, A AU - Larbalestier, D C AU - Ren, Z A AU - Yang, J AU - Dong, X L AU - Lu, W AU - Zhao, Z X T2 - Superconductor Science and Technology AB - Early studies have found quasi-reversible magnetization curves in polycrystalline bulk rare-earth iron oxypnictides that suggest either wide-spread obstacles to intergranular current or very weak vortex pinning. In the present study of polycrystalline samarium and neodymium rare-earth iron oxypnictide samples made by high pressure synthesis, the hysteretic magnetization is significantly enhanced. Magneto optical imaging and study of the field dependence of the remanent magnetization as a function of particle size both show that global currents over the whole sample do exist but that the intergranular and intragranular current densities have distinctively different temperature dependences and differ in magnitude by about 1000. Assuming that the highest current density loops are restricted to circulation only within grains leads to values of ~5 MA/cm2 at 5 K and self field, while whole-sample current densities, though two orders of magnitude lower are 1000-10000 A/cm2, some two orders of magnitude higher than in random polycrystalline cuprates. We cannot yet be certain whether this large difference in global and intragrain current density is intrinsic to the oxypnictides or due to extrinsic barriers to current flow, because the samples contain significant second phase, some of which wets the grain boundaries and produces evidences of SNS proximity effect in the whole sample critical current. DA - 2008/7/4/ PY - 2008/7/4/ DO - 10.1088/0953-2048/21/9/095008 VL - 21 IS - 9 SP - 095008 J2 - Supercond. Sci. Technol. OP - SN - 0953-2048 1361-6668 UR - http://dx.doi.org/10.1088/0953-2048/21/9/095008 DB - Crossref ER - TY - JOUR TI - Evidence for electromagnetic granularity in the polycrystalline iron-based superconductor LaO0.89F0.11FeAs AU - Yamamoto, A. AU - Jiang, J. AU - Tarantini, C. AU - Craig, N. AU - Polyanskii, A. A. AU - Kametani, F. AU - Hunte, F. AU - Jaroszynski, J. AU - Hellstrom, E. E. AU - Larbalestier, D. C. AU - Jin, R. AU - Sefat, A. S. AU - McGuire, M. A. AU - Sales, B. C. AU - Christen, D. K. AU - Mandrus, D. T2 - Applied Physics Letters AB - The recently discovered oxypnictide superconductors are layered, low carrier density compounds with many similarities to the high-Tc cuprates. An important question is whether they also exhibit weak-coupling across randomly oriented grain boundaries. In this work we show considerable evidence for such weak coupling by study of the dependence of magnetization in bulk and powdered samples. Bulk sample magnetization curves show very little hysteresis while remanent magnetization shows almost no sample size dependence, even after powdering. We conclude that these samples exhibit substantial electromagnetic granularity on a scale approximating the grain size, though we cannot yet determine whether this is intrinsic or extrinsic. DA - 2008/6/23/ PY - 2008/6/23/ DO - 10.1063/1.2952195 VL - 92 IS - 25 SP - 252501 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2952195 DB - Crossref ER - TY - JOUR TI - Two-band superconductivity in LaFeAsO0.89F0.11 at very high magnetic fields AU - Hunte, F. AU - Jaroszynski, J. AU - Gurevich, A. AU - Larbalestier, D. C. AU - Jin, R. AU - Sefat, A. S. AU - McGuire, M. A. AU - Sales, B. C. AU - Christen, D. K. AU - Mandrus, D. T2 - Nature AB - The recent synthesis of the superconductor LaFeAsO(0.89)F(0.11) with transition temperature T(c) approximately 26 K (refs 1-4) has been quickly followed by reports of even higher transition temperatures in related compounds: 41 K in CeFeAsO(0.84)F(0.16) (ref. 5), 43 K in SmFeAsO(0.9)F(0.1) (ref. 6), and 52 K in NdFeAsO(0.89)F(0.11) and PrFeAsO(0.89)F(0.11) (refs 7, 8). These discoveries have generated much interest in the mechanisms and manifestations of unconventional superconductivity in the family of doped quaternary layered oxypnictides LnOTMPn (Ln: La, Pr, Ce, Sm; TM: Mn, Fe, Co, Ni; Pn: P, As), because many features of these materials set them apart from other known superconductors. Here we report resistance measurements of LaFeAsO(0.89)F(0.11) at high magnetic fields, up to 45 T, that show a remarkable enhancement of the upper critical field B(c2) compared to values expected from the slopes dB(c2)/dT approximately 2 T K(-1) near T(c), particularly at low temperatures where the deduced B(c2)(0) approximately 63-65 T exceeds the paramagnetic limit. We argue that oxypnictides represent a new class of high-field superconductors with B(c2) values surpassing those of Nb(3)Sn, MgB(2) and the Chevrel phases, and perhaps exceeding the 100 T magnetic field benchmark of the high-T(c) copper oxides. DA - 2008/5/28/ PY - 2008/5/28/ DO - 10.1038/nature07058 VL - 453 IS - 7197 SP - 903-905 J2 - Nature LA - en OP - SN - 0028-0836 1476-4687 UR - http://dx.doi.org/10.1038/nature07058 DB - Crossref ER - TY - JOUR TI - Green light emitting diodes on a-plane GaN bulk substrates AU - Detchprohm, Theeradetch AU - Zhu, Mingwei AU - Li, Yufeng AU - Xia, Yong AU - Wetzel, Christian AU - Preble, Edward A. AU - Liu, Lianghong AU - Paskova, Tanya AU - Hanser, Drew T2 - Applied Physics Letters AB - We report the development of 520–540nm green light emitting diodes (LEDs) grown along the nonpolar a axis of GaN. GaInN∕GaN-based quantum well structures were grown in homoepitaxy on both, a-plane bulk GaN and a-plane GaN on r-plane sapphire. LEDs on GaN show higher, virtually dislocation-free crystalline quality and three times higher light output power when compared to those on r-plane sapphire. Both structures show a much smaller wavelength blue shift for increasing current density (&lt;10nm for 0.1to12.7A∕cm2) than conventional LEDs grown along the polar c axis. DA - 2008/6/16/ PY - 2008/6/16/ DO - 10.1063/1.2945664 VL - 92 IS - 24 SP - 241109 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2945664 DB - Crossref ER - TY - JOUR TI - Fabrication and characterization of native non-polar GaN substrates AU - Hanser, D. AU - Liu, L. AU - Preble, E.A. AU - Udwary, K. AU - Paskova, T. AU - Evans, K.R. T2 - Journal of Crystal Growth AB - Thick c-plane (0 0 0 1)-oriented native GaN boules that have been produced by hydride vapor phase epitaxy and non-polar native m-plane (1 1 0 0) and a-plane (1 1 2 0) GaN substrates have been sliced from these crystals using a multiwire saw. An optimized polishing procedure was used to achieve a smooth epi-ready surface morphology on the finished substrates, with an RMS roughness of 0.43 nm. The non-polar substrates had two types of structural characteristics in appearance : one group was uniform, transparent and nearly colorless; while the second group had regions of varying coloration resulting from transecting V-shape pitting defects in the bulk GaN crystal. These regions had different cathodoluminescence properties but similar dislocation densities of <106 cm−2. The native non-polar GaN substrates had orders of magnitude lower defect densities, including stacking faults, in comparison to heteroepitaxially grown quasi-substrates in non-polar direction on foreign substrates and subsequently delaminated. The structural characteristics demonstrated the current state-of-the-art in non-polar GaN substrate quality and additionally point at remaining improvement opportunities in substrate size and uniformity. DA - 2008/8// PY - 2008/8// DO - 10.1016/j.jcrysgro.2008.06.029 VL - 310 IS - 17 SP - 3953-3956 J2 - Journal of Crystal Growth LA - en OP - SN - 0022-0248 UR - http://dx.doi.org/10.1016/j.jcrysgro.2008.06.029 DB - Crossref KW - growth from vapor KW - single-crystal growth KW - nitrides ER - TY - JOUR TI - Enlargement of bulk non-polar GaN substrates by HVPE regrowth AU - Lai, K. Y. AU - Wheeler, V. D. AU - Grenko, J. A. AU - Johnson, M. A. L. AU - Hanser, A. D. AU - Preble, E. A. AU - Liu, L. AU - Paskova, T. AU - Evans, K. R. T2 - physica status solidi (c) AB - Abstract M‐plane non‐polar bulk GaN substrates were regrown by hydride vapour phase epitaxy (HVPE), aiming to enlarge their lateral size. The non‐polar GaN substrates were synthesized by growing thick GaN boules by HVPE along the c‐axis, and wafering transversely to expose non‐polar (m‐ or a‐plane) surfaces. Non‐polar GaN substrates obtained in this manner contains lower defect density comparing to those produced by heteroepitaxial growth. After the regrowth, substantial lateral expansion in [0001], [11 2 0] and [ 11 20] was observed. Threading dislocation densities were estimated by cathodoluminescence measured at the cross‐section areas. The dislocation densities in the substrate and the regrown areas were approximately 5×10 6 cm –2 and 1×10 6 cm –2 , respectively, indicating a comparable structural quality achieved by the regrowth. Non‐polar GaN substrates prepared by this process provide a promising method to fabricate devices for next generation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2008/5// PY - 2008/5// DO - 10.1002/pssc.200778743 VL - 5 IS - 6 SP - 1886-1888 J2 - phys. stat. sol. (c) LA - en OP - SN - 1610-1634 1610-1642 UR - http://dx.doi.org/10.1002/pssc.200778743 DB - Crossref ER - TY - JOUR TI - Thermal Stability of Hf-Based Gate Dielectric Stacks with Rare-Earth Oxide Capping Layers AU - LeBeau, JM AU - Jur, JS AU - Lichtenwalner, DJ AU - Kingon, AI AU - Klenov, DO AU - Stemmer, S T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/S1431927608084109 VL - 14 IS - S2 SP - 418-419 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927608084109 DB - Crossref ER - TY - JOUR TI - Fabrication of a GaN p/n lateral polarity junction by polar doping selectivity AU - Collazo, Ramón AU - Mita, Seiji AU - Rice, Anthony AU - Dalmau, Rafael AU - Wellenius, Patrick AU - Muth, John AU - Sitar, Zlatko T2 - physica status solidi (c) AB - Abstract The difference in surface energy between the Ga‐polar orientation and the N‐polar orientation of GaN translates into a completely different behavior for the incorporation of intentional and unintentional impurities. Oxygen is found to be an impurity with higher concentration in N‐polar films than in Ga‐polar films and is the cause for the high carrier concentration observed in N‐polar films. We fabricated a lateral p/n junction in GaN by the simultaneous growth of p‐ and n‐type regions, utilizing the doping selectivity of the two different polar domains, which resulted in an n‐type carrier concentration of 1.7x10 19 cm –3 with an electron hall mobility of 99 cm 2 /Vs in the N‐polar domains, and a p‐type carrier concentration of 1.1x10 17 cm –3 with a hole hall mobility of 12 cm 2 /Vs in the Ga‐polar domains. These junctions showed the characteristics that define a p/n junction: current rectification, electroluminescence, and photo‐effect. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2008/5// PY - 2008/5// DO - 10.1002/pssc.200778624 VL - 5 IS - 6 SP - 1977-1979 J2 - phys. stat. sol. (c) LA - en OP - SN - 1610-1634 1610-1642 UR - http://dx.doi.org/10.1002/pssc.200778624 DB - Crossref ER - TY - JOUR TI - The 3' proximal translational enhancer of Turnip crinkle virus binds to 60S ribosomal subunits AU - Stupina, V. A. AU - Meskauskas, A. AU - McCormack, J. C. AU - Yingling, Y. G. AU - Shapiro, B. A. AU - Dinman, J. D. AU - Simon, A. E. T2 - RNA AB - During cap-dependent translation of eukaryotic mRNAs, initiation factors interact with the 5′ cap to attract ribosomes. When animal viruses translate in a cap-independent fashion, ribosomes assemble upstream of initiation codons at internal ribosome entry sites (IRES). In contrast, many plant viral genomes do not contain 5′ ends with substantial IRES activity but instead have 3′ translational enhancers that function by an unknown mechanism. A 393-nucleotide (nt) region that includes the entire 3′ UTR of the Turnip crinkle virus (TCV) synergistically enhances translation of a reporter gene when associated with the TCV 5′ UTR. The major enhancer activity was mapped to an internal region of ∼140 nt that partially overlaps with a 100-nt structural domain previously predicted to adopt a form with some resemblance to a tRNA, according to a recent study by J.C. McCormack and colleagues. The T-shaped structure binds to 80S ribosomes and 60S ribosomal subunits, and binding is more efficient in the absence of surrounding sequences and in the presence of a pseudoknot that mimics the tRNA-acceptor stem. Untranslated TCV satellite RNA satC, which contains the TCV 3′ end and 6-nt differences in the region corresponding to the T-shaped element, does not detectably bind to 80S ribosomes and is not predicted to form a comparable structure. Binding of the TCV T-shaped element by 80S ribosomes was unaffected by salt-washing, reduced in the presence of AcPhe-tRNA, which binds to the P-site, and enhanced binding of Phe-tRNA to the ribosome A site. Mutations that reduced translation in vivo had similar effects on ribosome binding in vitro. This strong correlation suggests that ribosome entry in the 3′ UTR is a key function of the 3′ translational enhancer of TCV and that the T-shaped element contains some tRNA-like properties. DA - 2008/9/16/ PY - 2008/9/16/ DO - 10.1261/RNA.1227808 VL - 14 IS - 11 SP - 2379-2393 J2 - RNA LA - en OP - SN - 1355-8382 UR - http://dx.doi.org/10.1261/rna.1227808 DB - Crossref KW - cap-independent translation KW - internal ribosome entry site KW - Turnip crinkle virus KW - translational enhancer ER - TY - JOUR TI - Structural Domains within the 3' Untranslated Region of Turnip Crinkle Virus AU - McCormack, J. C. AU - Yuan, X. AU - Yingling, Y. G. AU - Kasprzak, W. AU - Zamora, R. E. AU - Shapiro, B. A. AU - Simon, A. E. T2 - Journal of Virology AB - ABSTRACT The genomes of positive-strand RNA viruses undergo conformational shifts that complicate efforts to equate structures with function. We have initiated a detailed analysis of secondary and tertiary elements within the 3′ end of Turnip crinkle virus (TCV) that are required for viral accumulation in vivo. MPGAfold, a massively parallel genetic algorithm, suggested the presence of five hairpins (H4a, H4b, and previously identified hairpins H4, H5, and Pr) and one H-type pseudoknot (Ψ 3 ) within the 3′-terminal 194 nucleotides (nt). In vivo compensatory mutagenesis analyses confirmed the existence of H4a, H4b, Ψ 3 and a second pseudoknot (Ψ 2 ) previously identified in a TCV satellite RNA. In-line structure probing of the 194-nt fragment supported the coexistence of H4, H4a, H4b, Ψ 3 and a pseudoknot that connects H5 and the 3′ end (Ψ 1 ). Stepwise replacements of TCV elements with the comparable elements from Cardamine chlorotic fleck virus indicated that the complete 142-nt 3′ end, and subsets containing Ψ 3 , H4a, and H4b or Ψ 3 , H4a, H4b, H5, and Ψ 2 , form functional domains for virus accumulation in vivo. A new 3-D molecular modeling protocol (RNA2D3D) predicted that H4a, H4b, H5, Ψ 3 , and Ψ 2 are capable of simultaneous existence and bears some resemblance to a tRNA. The related Japanese iris necrotic ring virus does not have comparable domains. These results provide a framework for determining how interconnected elements participate in processes that require 3′ untranslated region sequences such as translation and replication. DA - 2008/6/25/ PY - 2008/6/25/ DO - 10.1128/JVI.00416-08 VL - 82 IS - 17 SP - 8706-8720 J2 - Journal of Virology LA - en OP - SN - 0022-538X UR - http://dx.doi.org/10.1128/jvi.00416-08 DB - Crossref ER - TY - JOUR TI - RNAJunction: a database of RNA junctions and kissing loops for three-dimensional structural analysis and nanodesign T2 - Nucleic Acids Research AB - We developed a database called RNAJunction that contains structure and sequence information for RNA structural elements such as helical junctions, internal loops, bulges and loop-loop interactions. Our database provides a user-friendly way of searching structural elements by PDB code, structural classification, sequence, keyword or inter-helix angles. In addition, the structural data was subjected to energy minimization. This database is useful for analyzing RNA structures as well as for designing novel RNA structures on a nanoscale. The database can be accessed at: http://rnajunction.abcc.ncifcrf.gov/ DA - 2008/// PY - 2008/// DO - 10.1093/NAR/GKM842 UR - https://publons.com/publon/11561878/ ER - TY - JOUR TI - COMP 215-Explicit molecular dynamics simulations of kissing loop motif formed between TAR-RNA element of HIV-1 and aptamer T2 - Abstracts of Papers of the American Chemical Society DA - 2008/// PY - 2008/// UR - https://publons.com/publon/28057500/ ER - TY - CHAP TI - Protocols for the In Silico Design of RNA Nanostructures AU - Shapiro, Bruce A. AU - Bindewald, Eckart AU - Kasprzak, Wojciech AU - Yingling, Yaroslava T2 - Methods in Molecular Biology™ AB - Recent developments in the field of nanobiology have significantly expanded the possibilities for new modalities in the treatment of many diseases, including cancer. Ribonucleic acid (RNA) represents a relatively new molecular material for the development of these biologically oriented nanodevices. In addition, RNA nanobiology presents a relatively new approach for the development of RNA-based nanoparticles that can be used as crystallization substrates and scaffolds for RNA-based nanoarrays. Presented in this chapter are some methodological shaped-based protocols for the design of such RNA nanostructures. Included are descriptions and background materials describing protocols that use a database of three-dimensional RNA structure motifs; designed RNA secondary structure motifs; and a combination of the two approaches. An example is also given illustrating one of the protocols. PY - 2008/// DO - 10.1007/978-1-59745-480-3_7 SP - 93-115 OP - PB - Humana Press SN - 9781934115350 9781597454803 UR - http://dx.doi.org/10.1007/978-1-59745-480-3_7 DB - Crossref ER - TY - JOUR TI - Comparing Ion Distributions around RNA and DNA Helical and Loop-loop Motifs AU - Semichaevsky, Andrey V AU - Marlowe, Ashley E AU - Yingling, Yaroslava G T2 - MRS Proceedings DA - 2008/// PY - 2008/// DO - 10.1557/proc-1130-w05-05 VL - 1130 J2 - MRS Proc. LA - en OP - SN - 0272-9172 1946-4274 UR - http://dx.doi.org/10.1557/proc-1130-w05-05 DB - Crossref ER - TY - JOUR TI - Size Effects in the Vapor-Liquid Solid (VLS) Growth of Semiconductor Nanowires AU - Dickey, EC AU - Clark, TE AU - Zhang, X AU - Redwing, JM T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008 DA - 2008/8// PY - 2008/8// DO - 10.1017/s1431927608087382 VL - 14 IS - S2 SP - 6-7 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/s1431927608087382 DB - Crossref ER - TY - CONF TI - Modeling the Effect of Varying Electrical Voltage on the Plastic Deformation of a Single Asperity in Hot-Switched RF MEMS Contacts AU - Crill, John Wesley. AU - Irving, Douglas AU - Padgett, Cliff AU - Zikry, Mohommed AU - Brenner, Don T2 - 2008 MRS Fall Meetin C2 - 2008/// C3 - Materials Research Society Symposium Proceedings DA - 2008/// DO - 10.1557/proc-1137-ee10-15 PB - Materials Research Society UR - http://dx.doi.org/10.1557/proc-1137-ee10-15 DB - Crossref ER - TY - CONF TI - Atomic scale simulations of orientation of loading axis on the growth of voids at the onset of ductile failure in single crystal Cu AU - Dongare, Avinash M. AU - Rajendran, Arunachalam AU - LaMattina, Bruce AU - Zikry, Mohammed AU - Brenner, Donald W. T2 - 2008 MRS Fall Meetin C2 - 2008/// C3 - Materials Research Society Symposium Proceedings DA - 2008/// DO - 10.1557/proc-1137-ee08-09-w10-09 PB - Materials Research Society UR - http://dx.doi.org/10.1557/proc-1137-ee08-09-w10-09 DB - Crossref ER - TY - JOUR TI - Vertically aligned pearl-like carbon nanotube arrays for fiber spinning AU - PENG, HS AU - JAIN, M AU - LI, QW AU - al., T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - This work reports the first synthesis of highly aligned, pearl-like carbon nanotube arrays through a chemical vapor deposition process. The unique morphology of these carbon nanotubes makes it possible to spin them into macroscopic fibers with excellent mechanical and electrical properties. In addition, the interesting hollow structure of these nanotubes opens new applications such as nanoreactors. DA - 2008/// PY - 2008/// DO - 10.1021/ja077767c VL - 130 IS - 4 SP - 1130-+ ER - TY - JOUR TI - Tougher ultrafine grain Cu via high-angle grain boundaries and low dislocation density AU - ZHAO, YH AU - BINGERT, JF AU - ZHU, YT AU - al., T2 - APPLIED PHYSICS LETTERS AB - Although there are a few isolated examples of excellent strength and ductility in single-phase metals with ultrafine grained (UFG) structures, the precise role of different microstructural features responsible for these results is not fully understood. Here, we demonstrate that a large fraction of high-angle grain boundaries and a low dislocation density may significantly improve the toughness and uniform elongation of UFG Cu by increasing its strain-hardening rate without any concomitant sacrifice in its yield strength. Our study provides a strategy for synthesizing tough UFG materials. DA - 2008/// PY - 2008/// DO - 10.1063/1.2870014 VL - 92 IS - 8 ER - TY - JOUR TI - New deformation twinning mechanism generates zero macroscopic strain in nanocrystalline metals AU - WU, XL AU - LIAO, XZ AU - SRINIVASAN, SG AU - al., T2 - PHYSICAL REVIEW LETTERS AB - Macroscopic strain was hitherto considered a necessary corollary of deformation twinning in coarse-grained metals. Recently, twinning has been found to be a preeminent deformation mechanism in nanocrystalline face-centered-cubic (fcc) metals with medium-to-high stacking fault energies. Here we report a surprising discovery that the vast majority of deformation twins in nanocrystalline Al, Ni, and Cu, contrary to popular belief, yield zero net macroscopic strain. We propose a new twinning mechanism, random activation of partials, to explain this unusual phenomenon. The random activation of partials mechanism appears to be the most plausible mechanism and may be unique to nanocrystalline fcc metals with implications for their deformation behavior and mechanical properties. DA - 2008/// PY - 2008/// DO - 10.1103/PhysRevLett.100.095701 VL - 1 IS - 9 ER - TY - JOUR TI - Nanolayeired carbon/silica superstructures via organosilane assembly AU - PENG, HS AU - ZHU, YT AU - PETERSON, DE AU - al., T2 - ADVANCED MATERIALS AB - Advanced MaterialsVolume 20, Issue 6 p. 1199-1204 Communication Nanolayered Carbon/Silica Superstructures via Organosilane Assembly Huisheng Peng, Corresponding Author Huisheng Peng hpeng@lanl.gov Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118 (USA) Los Alamos National Laboratory, Los Alamos, NM 87545 (USA) Huisheng Peng, Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118 (USA). Yunfeng Lu, Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA 90095 (USA).Search for more papers by this authorYuntian Zhu, Yuntian Zhu Los Alamos National Laboratory, Los Alamos, NM 87545 (USA)Search for more papers by this authorDean E. Peterson, Dean E. Peterson Los Alamos National Laboratory, Los Alamos, NM 87545 (USA)Search for more papers by this authorYunfeng Lu, Corresponding Author Yunfeng Lu luucla@ucla.edu Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA 90095 (USA) Huisheng Peng, Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118 (USA). Yunfeng Lu, Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA 90095 (USA).Search for more papers by this author Huisheng Peng, Corresponding Author Huisheng Peng hpeng@lanl.gov Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118 (USA) Los Alamos National Laboratory, Los Alamos, NM 87545 (USA) Huisheng Peng, Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118 (USA). Yunfeng Lu, Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA 90095 (USA).Search for more papers by this authorYuntian Zhu, Yuntian Zhu Los Alamos National Laboratory, Los Alamos, NM 87545 (USA)Search for more papers by this authorDean E. Peterson, Dean E. Peterson Los Alamos National Laboratory, Los Alamos, NM 87545 (USA)Search for more papers by this authorYunfeng Lu, Corresponding Author Yunfeng Lu luucla@ucla.edu Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA 90095 (USA) Huisheng Peng, Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118 (USA). Yunfeng Lu, Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA 90095 (USA).Search for more papers by this author First published: 19 March 2008 https://doi.org/10.1002/adma.200701303Citations: 25AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Nanolayered carbon/silica superstructures with tunable morphologies (tubes, fibers, or spheres) and sizes (micro-sized or macroscopic) were synthesized by self-assembly of perylenedidimide-bridged silsesquioxane through an easy sol-gel process followed by carbonization. The derived nanocomposite materials show interesting electrical properties, i.e., the conductivity increases exponentially with temperature. Citing Literature Volume20, Issue6March 18, 2008Pages 1199-1204 RelatedInformation DA - 2008/// PY - 2008/// DO - 10.1002/adma.200701303 VL - 20 IS - 6 SP - 1199-+ ER - TY - CHAP TI - Long-length ultrafine-grained titanium rods produced by ECAP-Conform AU - Raaba, GI AU - Valiev, RZ AU - Gunderov, DV AU - Lowe, TC AU - Misra, A AU - Zhu, YT T2 - Nanomaterials By Severe Plastic Deformation Iv, Pts 1 and 2 PY - 2008/// VL - 584-586 SP - 80-85 PB - SE - ER - TY - JOUR TI - Influence of stacking-fault energy on microstructural characteristics of ultrafine-grain copper and copper-zinc alloys AU - BALOGH, L AU - UNGAR, T AU - ZHAO, Y AU - al., T2 - ACTA MATERIALIA AB - Experiments were conducted on samples of pure Cu and two Cu–Zn alloys to evaluate the influence of the stacking-fault energy (SFE) on microstructural development when processing using high-pressure torsion (HPT). Transmission electron microscopy, X-ray diffraction and hardness measurements were used for microstructural evaluation and the results show consistency between these techniques. Grain sizes in the nanometer range were formed at the edges of the HPT disks, larger submicrometer grains were formed in the disk centers and the measured grain sizes decreased with decreasing SFE. There was negligible twinning in pure Cu but the densities of dislocations and twins increased with increasing Zn content and thus with decreasing SFE. The values of the Vickers microhardness were lower in the centers of the disks for the two Cu–Zn alloy and this is consistent with the low SFE and slow rates of recovery. DA - 2008/// PY - 2008/// DO - 10.1016/j.actamat.2007.10.053 VL - 56 IS - 4 SP - 809-820 KW - copper alloys KW - high-pressure torsion KW - severe plastic deformation KW - stacking-fault energy KW - X-ray diffraction ER - TY - JOUR TI - High tensile ductility and strength in bulk nanostructured nickel AU - ZHAO, YH AU - TOPPING, T AU - BINGERT, JF AU - al., T2 - ADVANCED MATERIALS DA - 2008/// PY - 2008/// VL - 20 IS - 16 SP - 3028-3033 ER - TY - JOUR TI - High ductility of ultrafine-grained steel via phase transformation AU - CHENG, S AU - CHOO, H AU - ZHAO, YH AU - al., T2 - JOURNAL OF MATERIALS RESEARCH DA - 2008/// PY - 2008/// DO - 10.1557/JMR.2008.0213 VL - 23 IS - 6 SP - 1578-1586 ER - TY - JOUR TI - Evolution of defect structures during cold rolling of ultrafine-grained Cu and Cu-Zn alloys: Influence of stacking fault energy AU - ZHAO, YH AU - HORITA, Z AU - LANGDON, TG AU - al., T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Samples of pure Cu, bronze (Cu–10 wt.% Zn) and brass (Cu–30 wt.% Zn) with stacking fault energies (SFE) of 78, 35, and 14 mJ/m2, respectively, were processed by high-pressure torsion (HPT) and by a combination of HPT followed by cold-rolling (CR). X-ray diffraction measurements indicate that a decrease in SFE leads both to a decrease in crystallite size and to increases in microstrain, dislocation and twin densities for the HPT and HPT + CR processed ultrafine-grained (UFG) samples. Compared with processing by HPT, subsequent processing by CR refines the crystallite size of all samples, increases the twin densities of UFG bronze and brass, and increases the dislocation density in UFG bronze. It also decreases the dislocation density in UFG brass and leads to an unchanged dislocation density in UFG copper. The results suggest there may be an optimum stacking fault energy for dislocation accumulation in UFG Cu–Zn alloys and this has important implications in the production of materials having reasonable strain hardening and good tensile ductility. DA - 2008/// PY - 2008/// DO - 10.1016/j.msea.2007.06.014 VL - 474 IS - 1-2 SP - 342-347 KW - copper KW - copper-zinc alloys KW - high-pressure torsion KW - severe plastic deformation KW - stacking fault energy KW - ultrafine-grained materials ER - TY - JOUR TI - Determining the optimal stacking fault energy for achieving high ductility in ultrafine-grained Cu-Zn alloys AU - ZHAO, YH AU - LIAO, XZ AU - HORITA, Z AU - al., T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Bulk ultrafine-grained (UFG) materials produced by severe plastic deformation (SPD) often have low ductility. A previous study demonstrated the possibility of lowering the stacking fault energy to simultaneously increase the strength and ductility. This paper demonstrates, there exists an optimal stacking fault energy for the best ductility in UFG Cu–Zn alloys processed by the same SPD processing. When the stacking fault energy is too low, the grain size lies below 15 nm after SPD processing and the stacking faults are saturated so that it is difficult to accumulate dislocations and deformation twins during the subsequent tensile testing. These results provide significant guidance for the future design of UFG and nanocrystalline alloys for achieving high ductilities. DA - 2008/// PY - 2008/// DO - 10.1016/j.msea.2007.11.074 VL - 493 IS - 1-2 SP - 123-129 KW - copper alloys KW - ductility KW - high-pressure torsion KW - severe plastic deformation KW - stacking fault energy ER - TY - CHAP TI - SYNTHESIS OF CERAMIC EUTECTICS USING MICROWAVE PROCESSING AU - Polotai, AV AU - Cheng, JP AU - Agrawal, DK AU - Dickey, EC AU - Cytron, S T2 - Advances in Ceramic Armor Iii PY - 2008/// VL - 28 SP - 127-133 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000284980300011&KeyUID=WOS:000284980300011 ER - TY - CHAP TI - Stability of Ni Electrodes and Ni-BaTiO3 Interface Evolution in Ultrathin BME MLCCs AU - Polotai, AV AU - Shay, DP AU - Yang, GY AU - Dickey, EC AU - Randall, CA T2 - 2008 17th Ieee International Symposium on the Applications of Ferroelectrics PY - 2008/// SP - 3-4 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000270584000002&KeyUID=WOS:000270584000002 ER - TY - JOUR TI - Raman scattering from Si1-xGex alloy nanowires AU - Lu, QJ AU - Adu, KW AU - Gutierrez, HR AU - Chen, GG AU - Lew, KK AU - Nimmatoori, P AU - Zhang, X AU - Dickey, EC AU - Redwing, JM AU - Eklund, PC T2 - Journal of Physical Chemistry C AB - We present Raman scattering results on crystalline Si1-xGex nanowires (0 < x < 1) grown by the vapor−liquid−solid growth mechanism using chemical vapor deposition. Typical nanowire diameters and lengths were in the range 80−110 nm and 15−40 μm, respectively. Three strong Raman bands were observed and identified as perturbed Si−Si (∼500 cm-1) modes, perturbed Ge−Ge (∼280 cm-1) modes, and intermediate frequency (∼400 cm-1) modes assigned to Si−Ge clusters. A broad band is observed in the range ∼75−110 cm-1 that is assigned to transverse acoustic modes. The compositional dependence of these Raman bands is similar to what is observed in bulk material and is also found to be in very good agreement with the recently calculated vibrational density of states for Si1-xGex nanoparticles. DA - 2008/// PY - 2008/// DO - 10.1021/jp074764d VL - 112 IS - 9 SP - 3209-3215 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000253512400011&KeyUID=WOS:000253512400011 ER - TY - JOUR TI - Laser Surface Processing of B4C-TiB2 Eutectic AU - Polotai, AV AU - Foreman, JF AU - Dickey, EC AU - Meinert, K T2 - International Journal of Applied Ceramic Technology AB - The formation of a directionally solidified non‐oxide eutectic surface layer based on the 75 mol% B 4 C and 25 mol% TiB 2 eutectic composition has been developed using a continuous‐wave, high‐power, CO 2 laser. To prevent the oxidation of nonoxide compounds and to reduce thermal stress formation, an atmospherically controlled furnace capable of back‐heating samples up to 1100°C during the laser processing has been employed. The effect of the laser scan rate on the eutectic microstructure formation is investigated. It is found that at relatively slow laser scan rates, ∼2–4 mm/s, the formation of a colony‐type eutectic microstructure with submicrometer scale features is observed. At higher heating rates up to 42 mm/s, disordered eutectic grains with nanometer‐scale TiB 2 lamellae form. The dependence of the TiB 2 interlamellar spacing on the crystallization rate in the laser solidified B 4 C–TiB 2 eutectic has the same general trend as in the eutectic produced by a floating zone method. However, this method allows the production of much smaller microstructural length scales, on the order of 100 nm, as a consequence of the high crystallization velocity. DA - 2008/// PY - 2008/// DO - 10.1111/j.1744-7402.2008.02229.x VL - 5 IS - 6 SP - 610-617 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000260544200009&KeyUID=WOS:000260544200009 ER - TY - JOUR TI - Interface Stoichiometry and Structure in Anodic Niobium Pentoxide AU - Olszta, Matthew J. AU - Dickey, Elizabeth C. T2 - Microscopy and Microanalysis AB - High-resolution transmission electron microscopy and electron energy loss spectroscopy (EELS) were performed on electrochemically anodized niobium and niobium oxide. Sintered anodes of Nb and NbO powders were anodized in 0.1 wt% H3PO4 at 10, 20, and 65 V to form surface Nb2O5 layers with an average anodization constant of 3.6+/-0.2 nm/V. The anode/dielectric interfaces were continuous and the dielectric layers were amorphous except for occurrences of plate-like, orthorhombic pentoxide crystallites in both anodes formed at 65 V. Using EELS stoichiometry quantification and relative chemical shifts of the Nb M4,5 ionization edge, a suboxide transition layer at the amorphous pentoxide interface on the order of 5 nm was detected in the Nb anodes, whereas no interfacial suboxide layers were detected in the NbO anodes. DA - 2008/9/16/ PY - 2008/9/16/ DO - 10.1017/S1431927608080756 VL - 14 IS - 5 SP - 451-458 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927608080756 DB - Crossref KW - electrolytic capacitor KW - niobium KW - niobium oxide KW - amorphous oxide KW - dielectric KW - HRTEM KW - EELS ER - TY - JOUR TI - Equilibrium strain-energy analysis of coherently strained core-shell nanowires AU - Trammell, TE AU - Zhang, X AU - Li, YL AU - Chen, LQ AU - Dickey, EC T2 - Journal of Crystal Growth AB - In order to continue the performance enhancement of Si-based semiconductor devices, the number of devices on a chip as well as the performance of those devices must continue to improve. One method for improving device functionality is the incorporation of strained Si–Ge heterostructures. While such heterostructures have been the focus of much research in planar Si processing, only recently has the fabrication of such heterostructures in nanoscale semiconductors been addressed. In particular, the fabrication of a Si–Ge radial nanowire heterostructure requires a consideration of the epitaxial stability of the shell on the underlying core nanowire. This work develops a model for the strain state of a radial nanowire heterostructure, focusing on the particular example of Si–Ge. The behavior of the radial nanowire heterostructure is compared to that of a planar heterostructure, and we find that much higher strains can be achieved in the nanowire geometry. DA - 2008/// PY - 2008/// DO - 10.1016/j.jcrysgro.2008.02.037 VL - 310 IS - 12 SP - 3084-3092 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000257006800024&KeyUID=WOS:000257006800024 KW - stresses KW - solid phase epitaxial KW - semiconductor materials KW - field effect transistors ER - TY - JOUR TI - Effects of a compositionally graded buffer layer on stress evolution during GaN and AlxGa1-xN MOCVD on SiC substrates AU - Acord, JD AU - Weng, XJ AU - Dickey, EC AU - Snyder, DW AU - Redwing, JM T2 - Journal of Crystal Growth AB - In situ substrate curvature measurements were used to monitor stress evolution during metal organic chemical vapor deposition (MOCVD) of AlxGa1−xN epilayers (x=0, 0.5, 0.7) on 6H-SiC (0 0 0 1) substrates that were grown using compositionally graded AlN to AlxGa1−xN buffer layers. The results were compared to identical growths carried out using thin (∼80 nm) AlN buffer layers in order to assess the impact of the graded layer on the mean film stress and structural properties of AlxGa1−xN. Compositionally graded (AlN–GaN) layers effectively increased the mean compressive stress in GaN epilayers grown on SiC compared to samples grown on AlN buffer layers, with the mean stress in the GaN layer increasing with buffer layer thickness. Increasing buffer thickness correlated with a decrease in the threading dislocation density measured by plan-view-TEM. In contrast, the mean stress in high Al-fraction AlxGa1−xN epilayers (x=0.5 and 0.7) was not significantly altered by the use of AlN to AlxGa1−xN graded buffer layers and in some cases, the graded layer leads to a decrease in mean compressive stress in the films. The differences in stress evolution are explained in terms of the available compressive strain energy, which is suggested to be responsible for dislocation bending observed in the GaN graded layer samples. DA - 2008/// PY - 2008/// DO - 10.1016/j.jcrysgro.2007.11.153 VL - 310 IS - 7-9 SP - 2314-2319 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000255843200185&KeyUID=WOS:000255843200185 KW - stresses KW - metalorganic vapor phase epitaxy KW - nitrides KW - semiconducting III-V materials ER - TY - JOUR TI - Effect of Heating Rates during Sintering on the Electrical Properties of Ultra-Thin NiBaTiO3 Multilayer Ceramic Capacitors AU - Polotai, Anton V. AU - Fujii, Ichiro AU - Shay, Dennis P. AU - Yang, Gai-Ying AU - Dickey, Elizabeth C. AU - Randall, Clive A. T2 - Journal of the American Ceramic Society AB - Microstructural control in thin‐layer multilayer ceramic capacitors (MLCCs) is one of the present day challenges for increasing capacitive volumetric efficiency and high voltage dielectric properties. The present paper continues a series of investigations aimed at engineering the stability of ultra‐thin Ni layers in base‐metal electrode MLCCs. A kinetic approach based on the control of sintering profiles is found to not only prevent Ni electrode discontinuities, but also to significantly improve the interfacial electrical properties. Increasing sintering heating rates from 200 to 3000°C/h leads to a decrease in its temperature dependence of capacitance. Faster heating rates also reduce the BaTiO 3 grain size, which is beneficial to the reliability of multilayer capacitors. A direct correlation between heating rates, the thickness of an interfacial (Ni, Ba, and Ti) alloy reaction layer and the interfacial contact resistance has been observed. The decrease in the alloy layer thickness at high heating rates leads to an increased effective Schottky barrier height between the dielectric and electrode toward its theoretical value of 1.25 eV for pure Ni–BaTiO 3 interfaces. DA - 2008/6// PY - 2008/6// DO - 10.1111/j.1551-2916.2008.02517.x VL - 91 IS - 8 SP - 2540-2544 SN - 0002-7820 1551-2916 UR - http://dx.doi.org/10.1111/j.1551-2916.2008.02517.x ER - TY - JOUR TI - Diameter Dependent Growth Rate and Interfacial Abruptness in Vapor–Liquid–Solid Si/Si1−xGex Heterostructure Nanowires AU - Clark, Trevor E. AU - Nimmatoori, Pramod AU - Lew, Kok-Keong AU - Pan, Ling AU - Redwing, Joan M. AU - Dickey, Elizabeth C. T2 - Nano Letters AB - A strong diameter dependence is observed in the interfacial abruptness and growth rates in Si/Si 1- x Ge x axial heterostructure nanowires grown via Au-mediated low pressure CVD using silane and germane precursors. The growth of these nanowires has similarities to that of heterostructure thin films with similar compositional interfacial broadening, which increases with and is on the order with diameter. This broadening may reveal a fundamental challenge to fabrication of abrupt heterostructures via VLS growth. DA - 2008/4// PY - 2008/4// DO - 10.1021/nl072849k VL - 8 IS - 4 SP - 1246–1252 SN - 1530-6984 1530-6992 UR - http://dx.doi.org/10.1021/nl072849k ER - TY - JOUR TI - Analysis of Si1-xGex : H thin films with graded composition and structure by real time spectroscopic ellipsometry AU - Podraza, NJ AU - Li, J AU - Wronski, CR AU - Dickey, EC AU - Horn, MW AU - Collins, RW T2 - Physica Status Solidi a-Applications and Materials Science AB - Abstract Silicon‐germanium (Si 1− x Ge x :H) thin films have been prepared by plasma enhanced chemical vapor deposition of SiH 4 and GeH 4 and measured during growth using real time spectroscopic ellipsometry. A two‐layer virtual interface analysis has been applied to study the structural evolution of Si 1− x Ge x :H films that initially nucleate in the amorphous (a) phase, but evolve to the microcrystalline (μc) phase with accumulated thickness. The compositional evolution of alloy‐graded a‐Si 1− x Ge x :H has been studied as well using similar methods. Both types of films are of interest for Si‐based photovoltaic devices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2008/// PY - 2008/// DO - 10.1002/pssa.200777876 VL - 205 IS - 4 SP - 892-895 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000255702600041&KeyUID=WOS:000255702600041 ER - TY - CHAP TI - Analysis of Compositionally and Structurally Graded Si:H and Si1-xGex:H Thin Films by Real Time Spectroscopic Ellipsometry AU - Podraza, NJ AU - Li, J AU - Wronski, CR AU - Horn, MW AU - Dickey, EC AU - Collins, RW T2 - Amorphous and Polycrystalline Thin-Film Silicon Science and Technology-2008 PY - 2008/// VL - 1066 SP - 253-258 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000261398700036&KeyUID=WOS:000261398700036 ER - TY - JOUR TI - Theoretical studies of defects states in GaSe and GaTe AU - Rak, Zsolt AU - Mahanti, S. D. AU - Mandal, Krishna C. AU - Fernelius, N. C. AU - Burger, A AU - Franks, LA AU - James, RB T2 - Hard X-Ray, Gamma-Ray, and Neutron Detector Physics X AB - We have investigated the electronic structures of bulk GaSe and GaTe as well as the nature of defect states associated with substitutional impurities and vacancies in GaSe and GaTe. These calculations were done using <i>ab initio</i> density functional theory and supercell models. We find that the Ga-Ga dimers play an important role in the formation of defect states. Analysis of the charge densities and the band structures associated with the defect states indicates that they are strongly localized. Theoretical results are in good agreement with experiment for CdGa and VGa in GaSe and for VGa in GaTe. The effect of spin-orbit interaction on the band structure of GaTe has been investigated; it is found that the top valence bands at the Γ-point shift up in energy by ~ 0.1 eV due to the mixing of Te px-py and pz bands. DA - 2008/// PY - 2008/// DO - 10.1117/12.796229 VL - 7079 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-57549108317&partnerID=MN8TOARS KW - defects KW - wide gap semiconductors KW - ab initio calculations KW - electronic structure ER - TY - JOUR TI - Size limitations for the formation of ordered striped nanoparticles AU - CARNEY, RP AU - DEVRIES, GA AU - DUBOIS, C AU - KIM, H AU - KIM, JY AU - SINGH, C AU - GHORAI, PK AU - TRACY, JB AU - STILES, RL AU - MURRAY, RW AU - GLOTZER, SC AU - STELLACCI, F T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - A combination of immiscible molecules in the ligand shell of a gold nanoparticle (NP) has been shown to phase separate into a rippled structure; this phase separation can be used to direct the assembly of the NPs into chains. Here we demonstrate that only NPs within a certain size range can form chains, and we conclude that the rippled morphology of the ligand shell also exists only within that given size range. We corroborate this result with simulations of the ligand arrangement on NPs of various sizes. DA - 2008/// PY - 2008/// DO - 10.1021/ja077383m VL - 130 IS - 3 SP - 798-+ UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000252426300010&KeyUID=WOS:000252426300010 ER - TY - JOUR TI - Nanoparticle MALDI-TOF mass spectrometry without fragmentation: Au-25(SCH2CH2Ph)(18) and mixed monolayer Au-25(SCH2CH2Ph)(18-x)(L)(x) AU - DASS, A AU - STEVENSON, A AU - DUBAY, GR AU - TRACY, JB AU - MURRAY, RW T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Intact molecular ions of the organothiolate-protected nanoparticle Au25(SCH2CH2Ph)18, including their isotopic resolution, can be observed at 7391 Da as 1- and 1+ ions in negative and positive mode, respectively, by MALDI-TOF mass spectrometry when using a tactic of threshold laser pulse intensities and trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) as matrix. Previous MALDI-TOF studies of Au nanoparticles using other matrices have encountered extensive fragmentation of nanoparticle as well as thiolate ligands. Absence of fragmentation enables precise determination of the distribution of mixed monolayer compositions on nanoparticles prepared by ligand exchange reactions and by synthesis using thiol mixtures. Reaction conditions producing mixed monolayers containing only one or a small number of usefully functional ligands can be readily identified. At increased laser pulse intensity, the first fragmentation step(s) for the Au25(SCH 2CH2Ph)18 nanoparticle results in losses of AuL units and, in particular, loss of Au4(SCH2CH2Ph)4. DA - 2008/// PY - 2008/// DO - 10.1021/ja710323t VL - 130 IS - 18 SP - 5940-5946 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000255629400033&KeyUID=WOS:000255629400033 ER - TY - JOUR TI - NUCL 27-Magnetic and metallic monolayer-protected nanoparticles AU - TRACY, JB T2 - ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY DA - 2008/// PY - 2008/// VL - 236 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000270256305758&KeyUID=WOS:000270256305758 ER - TY - JOUR TI - Incorporation of iron oxide nanoplarticles and quantum dots into silica microspheres AU - INSIN, N AU - TRACY, JB AU - LEE, H AU - ZIMMER, JP AU - WESTERVELT, RM AU - BAWENDI, MG T2 - ACS NANO AB - We describe the synthesis of magnetic and fluorescent silica microspheres fabricated by incorporating maghemite (γ-Fe2O3) nanoparticles (MPs) and CdSe/CdZnS core/shell quantum dots (QDs) into a silica shell around preformed silica microspheres. The resultant ∼500 nm microspheres have a narrow size distribution and show uniform incorporation of QDs and MPs into the shell. We have demonstrated manipulation of these microspheres using an external magnetic field with real-time fluorescence microscopy imaging. DA - 2008/// PY - 2008/// DO - 10.1021/nn700344x VL - 2 IS - 2 SP - 197-202 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000253503300008&KeyUID=WOS:000253503300008 KW - silica microspheres KW - superparamagnetic KW - fluorescent KW - iron oxide nanoparticles KW - quantum dots KW - magnetic manipulation KW - multifunctional microspheres ER - TY - JOUR TI - INOR 620-Exchange bias and the magnetic properties of oxidized nickel nanoparticles AU - WANG, JW AU - JOHNSTON-PECK, AC AU - TRACY, JB T2 - ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY DA - 2008/// PY - 2008/// VL - 236 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000270256306531&KeyUID=WOS:000270256306531 ER - TY - JOUR TI - Gold nanoparticles with perfluorothiolate ligands AU - DASS, A AU - GUO, R AU - TRACY, JB AU - BALASUBRAMANIAN, R AU - DOUGLAS, AD AU - MURRAY, RW T2 - LANGMUIR AB - Two syntheses of gold nanoparticles with fluorinated alkyl and aryl thiolate ligands are reported. The fluorous Au nanoparticles are smaller than previous gold fluor-capped examples, and are in the 44−75 Au atom size range. Fluoroalkyl thiolate-protected (1H,1H,2H,2H-perfluorodecanethiolate) nanoparticles synthesized by a Brust reaction are a mixture of (mainly) ∼8.5 kDa (ca. 44 core atoms) and ∼14 kDa (ca. 75 core atoms) species, by MALDI-mass spectrometry. This composition is consistent with thermogravimetric analysis (TGA) results of the ligand shell composition. 19F NMR spectra display a progressive line broadening of resonances for fluorine sites closer to the Au core. A second synthetic route used a (ligand replacement) reaction of pentafluorobenzenethiol with Au55(PPh3)12Cl6. The exchange is (as previously observed for nonfluorinated thiols) accompanied by nanoparticle core size changes to produce a polydisperse mixture within which a Au75 core species could be electrochemically discerned by its characteristic 0.74 V electrochemical energy gap. Further characterization of the polydisperse nanoparticle product was done by HPLC, TEM, TGA, optical spectroscopy, and NMR data. Both varieties of fluorous nanoparticles exhibit solubilities typical of perfluorinated materials, as opposed to proteo versions. DA - 2008/// PY - 2008/// DO - 10.1021/la702651y VL - 24 IS - 1 SP - 310-315 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000251916100046&KeyUID=WOS:000251916100046 ER - TY - BOOK TI - Finite plastic deformation of crystalline solids (paperback re-issue) AU - Havner, K. S. DA - 2008/// PY - 2008/// PB - Cambridge: Cambridge University Press ER - TY - JOUR TI - Prediction of Energies of <100> Tilt Boundaries in Al-Pb Alloy AU - Purohit, Y. AU - Irving, D. L. AU - Scattergood, R. O. AU - Brenner, D. W. T2 - Materials Research Society Symposium Proceedings DA - 2008/// PY - 2008/// VL - 1056E SP - 1056-HH01-105610 ER - TY - JOUR TI - MEMS Lubrication: An atomistic perspective of a bound+ mobile lubricant' AU - Irving, D. L. AU - Brenner, D. W. T2 - Materials Research Society Symposium Proceedings DA - 2008/// PY - 2008/// VL - 1052 SP - 29-34 ER - TY - JOUR TI - Quantification in dynamic SIMS: Current status and future needs AU - Stevie, F. A. AU - Griffis, D. P. T2 - APPLIED SURFACE SCIENCE AB - Dynamic SIMS has made great strides in quantification. The use of ion-implanted standards has made quantification routine for any element in a wide range of matrices. Both contaminant and matrix measurements can be reliably quantified in the same depth profile for selected multi-element substrates, such as SiGe and AlGaN. Dose measurements with less than 1% reproducibility have been demonstrated for magnetic sector, quadrupole, and time-of-flight instruments. Progress has been made in quantification at the surface, at interfaces, in thin layers, in insulators, within small areas, and for two and three dimensions. Current challenges include quantification in a proliferation of layers, interfaces, and elements, and obtaining quantitative information from the smallest possible area. Analyses using complementary techniques will be useful for these difficult SIMS measurements. Focused ion beam specimen preparation has shown promise for small area and three-dimensional analyses. Developments in ion sources show potential for small area analysis using focused ion beam SIMS. DA - 2008/12/15/ PY - 2008/12/15/ DO - 10.1016/j.apsusc.2008.05.041 VL - 255 IS - 4 SP - 1364-1367 SN - 0169-4332 KW - Quantification KW - Ion implantation KW - Complementary methods KW - Focused ion beam (FIB) ER - TY - JOUR TI - Influence of pulse plating parameters on the synthesis and preferred orientation of nanocrystalline zinc from zinc sulfate electrolytes AU - Youssef, K. M. AU - Koch, C. C. AU - Fedkiw, P. S. T2 - ELECTROCHIMICA ACTA AB - The influence of pulse electrodeposition parameters (current on-time Ton, current off-time Toff, and pulse current density Jp) was investigated on the surface morphology and grain size of zinc electrodeposited from a sulfate bath containing polyacrylamide and thiourea additives. The grain size and surface morphology of zinc deposits were studied by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), and the preferred orientation of the deposits was studied by X-ray diffraction. At constant current off-time and pulse current density, the grain size decreased asymptotically with increasing current on-time. In contrast, increase in the current off-time at constant current on-time and pulse current density resulted in grain growth. A progressive decrease of the grain size was observed with increasing pulse current density at constant current on-time and off-time. Nanocrystalline zinc with an average grain size of 38 nm was obtained at a pulse current density of 1200 mA/cm2. The crystallographic orientations developed were correlated with the change in the cathodic overpotential, the angle between the preferred oriented plane and the lowest energy of formation plane (0 0 0 2), and the pulse electrodeposition parameters. DA - 2008/12/30/ PY - 2008/12/30/ DO - 10.1016/j.electacta.2008.07.048 VL - 54 IS - 2 SP - 677-683 SN - 1873-3859 KW - Pulse electrodeposition KW - Nanocrystalline KW - zinc KW - Preferred orientation ER - TY - JOUR TI - Carrier lifetime limitation defects in polycrystalline silicon ribbons grown on substrate (RGS) AU - Lu, Jinggang AU - Rozgonyi, George A. AU - Schonecker, Axel T2 - MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING AB - Carrier lifetime limitation defects in polycrystalline silicon ribbons have been examined in samples with high oxygen and carbon content. Infrared spectroscopy showed that essentially all supersaturated oxygen impurities precipitated within 1 h annealing at over 800 °C. Preferential defect etching revealed that a much higher density of oxygen precipitates were generated in dislocation-free grains than in those highly dislocated (105–107 cm−2) ones. Correlated with electron-beam-induced current imaging, we found that oxygen precipitates are the dominant carrier recombination defects in dislocation-free grains, while dislocations are the lifetime killer for highly dislocated grains. It is suggested that eliminating dislocations alone will not improve the carrier lifetime, considering that a higher density of oxygen precipitates formed in the absence of dislocation-related heterogeneous nucleation sites will significantly degrade the carrier lifetime. DA - 2008/2// PY - 2008/2// DO - 10.1016/j.mssp.2008.07.001 VL - 11 IS - 1 SP - 20-24 SN - 1873-4081 KW - Polycrystalline silicon KW - Dislocations KW - Oxygen precipitation KW - EBIC KW - Carrier lifetime ER - TY - JOUR TI - Review of structured thin films in wide bandgap semiconductors: pendeo-epitaxy of GaN and AlGaN AU - Gehrke, T. T2 - Journal of Nanophotonics DA - 2008/// PY - 2008/// VL - 2 ER - TY - JOUR TI - Nanoencapsulation and Stabilization of Single-Molecule/Particle Electronic Nanoassemblies Using Low-Temperature Atomic Layer Deposition AU - Na, Jeong-Seok AU - Ayres, Jennifer A. AU - Chandra, Kusum L. AU - Gorman, Christopher B. AU - Parsons, Gregory N. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - This work addresses a significant challenge in engineered molecular systems regarding both understanding and controlling the stability of molecule/nanoparticle nanostructures under ambient exposure. Results deal specifically with molecular electronic junctions, where electronic contacts and transport are known to be sensitive to sample history and ambient exposure. We demonstrate that low-temperature atomic layer deposition can gently encapsulate and stabilize molecular electronic junctions, making it feasible to handle and transport junctions in air for many days with minimal change in electronic conduction. These findings indicate the potential for long-term stability of advanced synthetic nanoparticle/molecule nanoconstructs. For this study, conductivity through nanoparticle/molecule/nanoparticle junctions is analyzed and found to be consistent with nonresonant charge tunneling through a single or a small number of oligomeric phenylene ethynylene molecules in the electrical junction. The conductivity was stable in vacuum and inert gas, but under ambient exposure, the current initially decreased, then increased rapidly, followed by a slower rise, reaching a value exceeding 10 times larger than initially measured. After encapsulating functional devices using atomic layer deposition of aluminum oxide thin films at 30−50 °C, the junction showed conductance similar to the precoated values, and the current remained unchanged after more than 15 days under ambient exposure. The presence of the molecule junction after encapsulation was confirmed by the observed transition to Fowler−Nordheim tunneling and analysis of junction breakdown at high fields. The high conformality, precise thickness control, and low-temperature compatibility of the atomic layer deposition method make it uniquely qualified to stabilize and protect molecular junctions and systems. DA - 2008/12/25/ PY - 2008/12/25/ DO - 10.1021/jp8066298 VL - 112 IS - 51 SP - 20510-20517 SN - 1932-7447 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000261835000061&KeyUID=WOS:000261835000061 ER - TY - JOUR TI - Structural materials for Gen-IV nuclear reactors: Challenges and opportunities AU - Murty, K. L. AU - Charit, I. T2 - JOURNAL OF NUCLEAR MATERIALS AB - Generation-IV reactor design concepts envisioned thus far cater toward a common goal of providing safer, longer lasting, proliferation-resistant and economically viable nuclear power plants. The foremost consideration in the successful development and deployment of Gen-IV reactor systems is the performance and reliability issues involving structural materials for both in-core and out-of-core applications. The structural materials need to endure much higher temperatures, higher neutron doses and extremely corrosive environment, which are beyond the experience of the current nuclear power plants. Materials under active consideration for use in different reactor components include various ferritic/martensitic steels, austenitic stainless steels, nickel-base superalloys, ceramics, composites, etc. This paper presents a summary of various Gen-IV reactor concepts, with emphasis on the structural materials issues depending on the specific application areas. This paper also discusses the challenges involved in using the existing materials under both service and off-normal conditions. Tasks become increasingly complex due to the operation of various fundamental phenomena like radiation-induced segregation, radiation-enhanced diffusion, precipitation, interactions between impurity elements and radiation-produced defects, swelling, helium generation and so forth. Further, high temperature capability (e.g. creep properties) of these materials is a critical, performance-limiting factor. It is demonstrated that novel alloy and microstructural design approaches coupled with new materials processing and fabrication techniques may mitigate the challenges, and the optimum system performance may be achieved under much demanding conditions. DA - 2008/12/15/ PY - 2008/12/15/ DO - 10.1016/j.jnucmat.2008.08.044 VL - 383 IS - 1-2 SP - 189-195 SN - 0022-3115 ER - TY - JOUR TI - Static strain aging and dislocation-impurity interactions in irradiated mild steel AU - Murty, K. L. AU - Charit, I. T2 - JOURNAL OF NUCLEAR MATERIALS AB - Interactions between dislocations and interstitial impurity atoms lead to strain aging phenomenon in ferritic steels that are affected by the defects produced during neutron radiation exposure. We present here results on static strain aging in a silicon-killed mild steel before and after neutron irradiation. It is noted that the degree of strain aging (as measured by the yield point following restraining) decreased with increasing neutron dose resulting in essentially non-aging type at the highest dose (∼1019 n/cm2). The strain aging kinetics were investigated using data at various aging temperatures and were found to be unaffected by the neutron radiation exposure. These experimental results are compared to those observed in dry hydrogen treated (partially denitrided) samples and are correlated with models on Cottrell locking. DA - 2008/12/1/ PY - 2008/12/1/ DO - 10.1016/j.jnucmat.2008.08.008 VL - 382 IS - 2-3 SP - 217-222 SN - 0022-3115 ER - TY - JOUR TI - Stabilization of nanocrystalline grain sizes by solute additions AU - Koch, C. C. AU - Scattergood, R. O. AU - Darling, K. A. AU - Semones, J. E. T2 - JOURNAL OF MATERIALS SCIENCE DA - 2008/12// PY - 2008/12// DO - 10.1007/s10853-008-2870-0 VL - 43 IS - 23-24 SP - 7264-7272 SN - 1573-4803 ER - TY - JOUR TI - Special issue: Ultrafine-grained materials preface AU - Zhu, Y. T. AU - Estrin, Y. AU - Langdon, T. G. AU - Liao, X. Z. AU - Lowe, T. C. AU - Shan, Z. W. AU - Valiev, R. Z. T2 - Journal of Materials Science DA - 2008/// PY - 2008/// VL - 43 IS - 23-24 SP - 7255-7256 ER - TY - JOUR TI - In situ Growth of Pd Nanoparticles in Crosslinked Polymer Matrices AU - Aberg, Christopher M. AU - Seyam, Mohamed A. AU - Lassell, Scott A. AU - Bronstein, Lyudmila M. AU - Spontak, Richard J. T2 - MACROMOLECULAR RAPID COMMUNICATIONS AB - Abstract Polymer nanocomposites continue to receive considerable attention as multifunctional hybrid materials, with most nanocomposites fabricated by physical dispersion of surface‐functionalized nanoscale objects. In this study, we explore the viability of growing Pd‐containing nanoparticles from Na 2 PdCl 4 in two different polymers: hypercrosslinked polystyrene (HPS) and an aromatic polyimide (PIm). In HPS, single Pd‐containing nanoparticles possessing a relatively narrow size distribution (ca. 1–4 nm) form upon reduction of the divalent PdCl ions. Single nanoparticles with a broad size distribution ranging from ≈2 to 16 nm develop in PIm, which simultaneously undergoes chemical crosslinking during ion reduction. Such hybrid materials hold promise in molecular catalysis and gas separation. magnified image DA - 2008/12/16/ PY - 2008/12/16/ DO - 10.1002/marc.200800505 VL - 29 IS - 24 SP - 1926-1931 SN - 1521-3927 KW - crosslinking KW - electron microscopy KW - membranes KW - nanoparticles KW - networks ER - TY - JOUR TI - Growth of biepitaxial zinc oxide thin films on silicon (100) using yttria-stabilized zirconia buffer layer AU - Aggarwal, Ravi AU - Jin, Chunming AU - Pant, Punam AU - Narayan, Jagdish AU - Narayan, Roger J. T2 - Applied Physics Letters AB - In this work, an approach for integrating zinc oxide thin films with Si(100) substrates using an epitaxial tetragonal yttria-stabilized zirconia buffer layer is reported. Selected area electron diffraction measurements revealed the following epitaxial relationship: [110]YSZ∥[100]Si and (001)YSZ∥(001)Si. X-ray diffraction studies demonstrated that subsequent growth of the zinc oxide thin film on the yttria-stabilized zirconia buffer layer occurred with the following epitaxial relationship: (0002)ZnO∥(001)YSZ. The full width at half maximum value for the (0002) peak of zinc oxide was small (∼0.16°), which indicated good crystalline quality. Transmission electron microscopy revealed that the zinc oxide thin film grew epitaxially on an yttria-stabilized zirconia buffer layer in two different orientations, where one orientation was rotated by 30° from the other. The orientation relationship in this case was [101¯0]ZnO∥[100]YSZ or [21¯1¯0]ZnO∥[100]YSZ and (0002)ZnO∥(001)YSZ. The biepitaxial growth of the zinc oxide thin film has been explained in the framework of domain matching epitaxy. Optical emission measurements showed a strong excitonic emission peak from the zinc oxide thin film at ∼377 nm. Minimal green band emission in the photoluminescence spectrum indicated that the concentration of point defects was low. Integration of epitaxial zinc oxide thin films with Si(100) substrates is an important step toward developing practical applications of zinc oxide in a variety of optoelectronic devices. DA - 2008/12/22/ PY - 2008/12/22/ DO - 10.1063/1.3050529 VL - 93 IS - 25 SP - 251905 SN - 0003-6951 KW - electron diffraction KW - II-VI semiconductors KW - photoluminescence KW - point defects KW - pulsed laser deposition KW - semiconductor epitaxial layers KW - transmission electron microscopy KW - wide band gap semiconductors KW - X-ray diffraction KW - yttrium compounds KW - zinc compounds KW - zirconium compounds ER - TY - JOUR TI - Epitaxial growth and Ohmic contacts in MgxZn1-xO/TiN/Si(111) heterostructures AU - Jin, Chunming AU - Wei, Wei AU - Zhou, Honghui AU - Yang, Tsung-Han AU - Narayan, Roger J. T2 - APPLIED PHYSICS LETTERS AB - In this work, the electronic properties of Mg0.1Zn0.9O∕TiN∕Si(111) heterostructures processed using pulsed laser deposition were examined. X-ray diffraction and transmission electron microscopy studies demonstrated epitaxial growth of the titanium nitride buffer layer and the Mg0.1Zn0.9O thin film. Transmission electron microscopy demonstrated a thin (∼5nm) spinel layer along the magnesium zinc oxide/titanium nitride interface. Current-voltage measurements revealed Ohmic contact behavior through the magnesium zinc oxide/titanium nitride interface. These results suggest that the titanium nitride buffer layer in the MgxZn1−xO∕TiN∕Si(111) heterostructure provides a buffer layer for integrating magnesium zinc oxide thin films with silicon substrates, which both enable epitaxial growth and serve as an Ohmic electrode for the magnesium zinc oxide thin film. DA - 2008/12/22/ PY - 2008/12/22/ DO - 10.1063/1.3054347 VL - 93 IS - 25 SP - SN - 1077-3118 KW - buffer layers KW - electrodes KW - elemental semiconductors KW - II-VI semiconductors KW - magnesium compounds KW - ohmic contacts KW - pulsed laser deposition KW - semiconductor epitaxial layers KW - semiconductor growth KW - semiconductor heterojunctions KW - semiconductor-insulator-semiconductor structures KW - silicon KW - titanium compounds KW - transmission electron microscopy KW - vapour phase epitaxial growth KW - wide band gap semiconductors KW - X-ray diffraction KW - zinc compounds ER - TY - JOUR TI - Sublimation growth of an in-situ-deposited layer in SiC chemical vapor deposition on 4H-SiC(1 1 (2)over-bar 0) AU - Bishop, S. M. AU - Reynolds, C. L., Jr. AU - Liliental-Weber, Z. AU - Uprety, Y. AU - Ebert, C. W. AU - Stevie, F. A. AU - Park, J. -S. AU - Davis, R. F. T2 - JOURNAL OF CRYSTAL GROWTH AB - Homoepitaxial growths of 4H-SiC(1 1 2¯ 0) epitaxial layers have been achieved using chemical vapor deposition from 1250 to 1600 °C and two process routes: (1) with and (2) without the addition of SiH4 and C2H4 to the growth ambient. An activation energy of 3.72 eV/atom (359 kJ/mol) was determined for the former route and associated with either reactions in the gas phase or the potential barrier associated with the temperature-dependent sticking coefficient. The activation energy for the latter route was 5.64 eV/atom (544 kJ/mol), which is consistent with published values for SiC sublimation epitaxy. Sublimation dominated the growth process at temperature ⩾1600 °C. The same effect resulted in the in-situ deposition of a thin film during the heating stage of route (1). At 1450 °C this layer was ∼100 nm thick and exhibited a specular surface microstructure with a roughness of 0.31 nm RMS. The in-situ-deposited layer was thus employed as an intermediate layer prior to epitaxial layer growth using route (1) at ∼1450 °C. Regions free of one- and two-dimensional defects were observed using cross-sectional transmission electron microscopy. Distinct interfaces were not observed between the substrate and the epitaxial layers. DA - 2008/12/15/ PY - 2008/12/15/ DO - 10.1016/j.jcrysgro.2008.09.200 VL - 311 IS - 1 SP - 72-78 SN - 1873-5002 KW - Characterization KW - Chemical vapor deposition processes KW - Hot-wall epitaxy KW - Silicon carbide KW - Semiconducting materials ER - TY - JOUR TI - Impact of Cu contamination on the electrical properties of a direct silicon bonded (110)/(100) interfacial grain boundary AU - Yu, X. G. AU - Lu, J. G. AU - Rozgonyi, G. T2 - Journal of Applied Physics DA - 2008/// PY - 2008/// VL - 104 IS - 11 ER - TY - JOUR TI - Barrier layer mechanism engineering in calcium copper titanate thin film capacitors through microstructure control AU - Paisley, E. A. AU - Losego, M. D. AU - Aygun, S. M. AU - Craft, H. S. AU - Maria, J. -P. T2 - JOURNAL OF APPLIED PHYSICS AB - A peak permittivity greater than 10 000 has been achieved for calcium copper titanate (CCT) thin films by engineering a thin film microstructure that maximizes space charge contributions to polarizability. This permittivity is an order of magnitude greater than previous polycrystalline thin film efforts. This unique microstructure control is accomplished using a chemical solution deposition process flow that produces highly dense parallel layers ∼100 nm in thickness. We observe a thickness dependent permittivity where the entire film thickness constitutes the conducting region of a barrier layer capacitor despite the presence of multiple grain boundaries within that thickness. The model predictions are in good agreement with experimental data and are consistent with existing literature reports. These trends in permittivity with dielectric thickness raise new questions regarding the nature of barrier layers in CCT—and specifically, these results suggest that grain boundaries may not always participate as high resistance interlayers. DA - 2008/12/1/ PY - 2008/12/1/ DO - 10.1063/1.3033166 VL - 104 IS - 11 SP - SN - 1089-7550 ER - TY - JOUR TI - Abnormal domain switching in Pb(Zr,Ti)O-3 thin film capacitors AU - Wu, A. Y. AU - Vilarinho, P. M. AU - Wu, D. AU - Gruverman, A. T2 - Applied Physics Letters DA - 2008/// PY - 2008/// VL - 93 IS - 26 ER - TY - JOUR TI - Surface water reactivity of polycrystalline MgO and CaO films investigated using x-ray photoelectron spectroscopy AU - Craft, H. S. AU - Collazo, R. AU - Losego, M. D. AU - Sitar, Z. AU - Maria, J. -P. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - The authors report a study comparing the surface reactivities of the alkaline earth oxides MgO and CaO with respect to water vapor under ultrahigh and high vacuum conditions. Using x-ray photoelectron spectroscopy and a series of in vacuo exposures spanning ∼10−10Torr vacuum, to 10−6Torr flowing oxygen, the extent of surface hydroxylation was investigated by monitoring the O 1s photoelectron line. After the most aggressive exposures, the MgO surface reacted to form a maximum hydroxyl coverage of ∼1.3 ML (monolayer), while the CaO surface reached a maximum coverage of ∼3.0 ML. Both surface hydroxides could be removed by in vacuo thermal anneals; exposure to 250 and 500°C were required for MgO and CaO, respectively. These results are framed in terms of the suitability of these oxides in complex oxide-compound semiconductor heteroepitaxial multifunctional devices and with respect to understanding the development of surface morphology in epitaxial 111-oriented CaO and MgO thin films. DA - 2008/11// PY - 2008/11// DO - 10.1116/1.3000058 VL - 26 IS - 6 SP - 1507-1510 SN - 0734-2101 KW - annealing KW - calcium compounds KW - epitaxial layers KW - magnesium compounds KW - monolayers KW - surface chemistry KW - surface morphology KW - X-ray photoelectron spectra ER - TY - JOUR TI - Suppression of Ge-O and Ge-N bonding at Ge-HfO2 and Ge-TiO2 interfaces by deposition onto plasma-nitrided passivated Ge substrates AU - Lee, S. AU - Long, J. P. AU - Lucovsky, G. AU - Luening, J. T2 - THIN SOLID FILMS AB - A study of changes in nano-scale morphology of thin films of nano-crystalline transition metal (TM) elemental oxides, HfO2 and TiO2, on plasma-nitrided Ge(100) substrates, and Si(100) substrates with ultra-thin (∼ 0.8 nm) plasma-nitrided Si suboxide, SiOx, x < 2, or SiON interfacial layers is presented. Near edge X-ray absorption spectroscopy (NEXAS) has been used to determine nano-scale morphology of these films by Jahn–Teller distortion removal of band-edge d-state degeneracies. These results identify a new and novel application for NEXAS based on the resonant character of the respective O K1 and N K1 edge absorptions. Their X-ray energy difference of > 150 eV is critical for this approach. DA - 2008/11/3/ PY - 2008/11/3/ DO - 10.1016/j.tsf.2008.08.099 VL - 517 IS - 1 SP - 155-158 SN - 0040-6090 KW - Ge/dielectric interfaces KW - Remote plasma nitridation of Ge KW - Band edge defects KW - Remote plasma deposition KW - Thermal annealing ER - TY - JOUR TI - Pulsed Laser Deposition of Nanoporous Cobalt Thin Films AU - Jin, Chunming AU - Nori, Sudhakar AU - Wei, Wei AU - Aggarwal, Ravi AU - Kumar, Dhananjay AU - Narayan, Roger J. T2 - JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY AB - Nanoporous cobalt thin films were deposited on anodized aluminum oxide (AAO) membranes at room temperature using pulsed laser deposition. Scanning electron microscopy demonstrated that the nanoporous cobalt thin films retained the monodisperse pore size and high porosity of the anodized aluminum oxide substrates. Temperature- and field-dependent magnetic data obtained between 10 K and 350 K showed large hysteresis behavior in these materials. The increase of coercivity values was larger for nanoporous cobalt thin films than for multilayered cobalt/alumina thin films. The average diameter of the cobalt nanograins in the nanoporous cobalt thin films was estimated to be approsimately 5 nm for blocking temperatures near room temperature. These results suggest that pulsed laser deposition may be used to fabricate nanoporous magnetic materials with unusual properties for biosensing, drug delivery, data storage, and other technological applications. DA - 2008/11// PY - 2008/11// DO - 10.1166/jnn.2008.483 VL - 8 IS - 11 SP - 6043-6047 SN - 1533-4899 KW - Magnetization Curves KW - Epitaxial Films KW - Magnetic Nano-Networks ER - TY - JOUR TI - Plastic deformation of ultrafine-grained 2.5Y-TZP exposed to a dc electric field with an air gap AU - Conrad, H. AU - Yang, Di AU - Becher, P. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Abstract The influence on the tensile flow stress of ultrafine-grained 2.5Y-TZP at 1450 °C by a dc electric field with an air gap between the negative electrodes and the positive specimen was determined in two test procedures: Type a, in which the field is applied continuously from the very beginning up to a fixed strain ɛ  ≈ 0.2 and Type b, in which the field is alternately applied and removed following the prestrain ɛ  ≈ 0.2 without and with the field. A larger reduction in the flow stress by the field occurred in the Type a test compared to the Type b. Moreover, a larger reduction occurred in the Type b test when the prestrain was with a field applied compared to without. Both of these behaviors are attributed to a retardation of dynamic grain growth by the field. The reduction in the flow stress by the field in the Type b test was in accord with a decrease in the electrochemical potential for the formation of vacancies corresponding to the lattice diffusion of the rate-controlling Zr ions. The results in the present tests were in general accord with those obtained previously in which both the positive and negative electrodes made direct contact with the specimen. This indicates that neither the orientation of the field nor the presence of an air gap has significant influence on the electric field dependence of the flow stress. DA - 2008/11/25/ PY - 2008/11/25/ DO - 10.1016/j.msea.2008.07.012 VL - 496 IS - 1-2 SP - 9-13 SN - 0921-5093 KW - Electric field KW - Debye length KW - Grain growth KW - Plastic deformation KW - Zirconia ER - TY - JOUR TI - Focused in beam fabrication of metallic nanostructures on end faces of optical fibers for chemical sensing applications AU - Dhawan, A. AU - Muth, J. F. AU - Leonard, D. N. AU - Gerhold, M. D. AU - Gleeson, J. AU - Vo-Dinh, T. AU - Russell, P. E. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Focused ion beam (FIB) fabrication of fiber optic sensors, mainly chemical sensors, which are based on plasmonics-active nanostructures formed on the cleaved tips of optical fibers, is reported. The nanostructures fabricated included nanoholes in optically thick metallic films as well as metallic nanopillars and nanorods. The sensing mechanism is based on detecting shifts in surface plasmon resonances (SPRs) associated with nanoholes in metallic films and localized SPRs of metallic nanopillars and nanorods, when the refractive index of the medium surrounding the nanostructures is changed. These sensors can be employed for the detection of chemical agents in air as well as liquid media surrounding the sensors. FIB milling was employed to fabricate ordered arrays of nanoholes in optically thick (100–240nm) metallic films deposited on cleaved end faces of multimode, four-mode, and single-mode optical fibers. Separately, metallic nanorods and nanopillars were formed by first depositing a metallic (gold or silver) film on tips of optical fibers, which was followed by FIB milling large area patterns to form freestanding nanorods and nanopillars. Utilizing FIB allows engineering nanostructure geometries, i.e., nanostructure shapes and sizes that are chosen based on the plasmon resonances associated with them. Formation of periodic arrays of nanoholes provides a means of tuning plasmon resonance peaks, associated with extraordinary transmission of light through the array of nanoholes in the metallic films, based on periodicity and shape of the nanoholes as well as on refractive index changes to form sensitive chemical sensors. DA - 2008/11// PY - 2008/11// DO - 10.1116/1.3013329 VL - 26 IS - 6 SP - 2168-2173 SN - 1071-1023 KW - chemical sensors KW - fibre optic sensors KW - focused ion beam technology KW - gold KW - metallic thin films KW - nanostructured materials KW - refractive index KW - silver KW - surface plasmon resonance ER - TY - JOUR TI - Comparative Raman and HRTEM Study of Nanostructured GaN Nucleation Layers and Device Layers on Sapphire (0001) AU - Pant, P. AU - Narayan, J. AU - Wushuer, A. AU - Manghnani, M. H. T2 - JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY DA - 2008/11// PY - 2008/11// DO - 10.1166/jnn.2008.334 VL - 8 IS - 11 SP - 5985-5992 SN - 1533-4880 KW - GaN KW - Nucleation Layer KW - Raman Spectroscopy KW - Stress ER - TY - JOUR TI - Chemical bonding and graded interfacial transition regions at transition metal, Hf(Zr),/high-k gate dielectric, Hf(Zr)O(2), interfaces AU - Lucovsky, G. AU - Whitten, J. L. T2 - THIN SOLID FILMS AB - One of the most significant and challenging process integration issues for high-k dielectrics is the replacement of poly-Si gates in CMOS devices with either dual metal gates, or a single mid-band gap metal. The issue is the stability of the metal gate/high-k gate dielectric interface with respect to post-deposition thermal processing. Ab initio quantum chemistry calculations address this issue, and two questions have been resolved, providing results that are consistent with the experiment. The interface between a metal gate electrode and a high gate electrode and oxide dielectric cannot be atomically abrupt after post-deposition thermal processing. Instead there must be a chemically-graded interfacial transition region that mitigates some of the benefits of replacing dual poly-Si gates by metals, except for gate-last processing. However, electrical stress and heating during device operation will be significant driving force atomic motion, and the formation of an interfacial transition region. DA - 2008/11/3/ PY - 2008/11/3/ DO - 10.1016/j.tsf.2008.08.034 VL - 517 IS - 1 SP - 343-345 SN - 0040-6090 KW - High-k dielectrics KW - Hf(Zr)O(2) KW - Transition metal KW - Chemical bonding KW - Graded interfacial regions KW - O-atom vacancies KW - Discrete band edge ER - TY - JOUR TI - Characterization of Pd/gamma-Al2O3 Catalysts Prepared Using [Pd(hfac)(2)] in Liquid CO2 AU - Kelly, M. Jason AU - Kim, Jaehoon AU - Roberts, George W. AU - Lamb, H. Henry T2 - TOPICS IN CATALYSIS DA - 2008/8// PY - 2008/8// DO - 10.1007/s11244-008-9075-2 VL - 49 IS - 3-4 SP - 178-186 SN - 1572-9028 KW - Palladium-alumina catalysts KW - Palladium hexafluoroacetylacetonate KW - Catalyst preparation KW - CO pulse chemisorption KW - Diffuse-reflectance infrared spectroscopy KW - X-ray absorption fine structure spectroscopy ER - TY - JOUR TI - Bulk defects in nano-crystalline and in non-crystalline HfO2-based thin film dielectrics AU - Lee, S. AU - Seo, H. AU - Lucovsky, G. AU - Fleming, L. B. AU - Ulrich, M. D. AU - Luening, J. T2 - THIN SOLID FILMS AB - Defect states in the form of band edge electron and hole traps in HfO2 nano-crystalline films are qualitatively different in two different length scale regimes. For grain sizes > 3–4 nm, they are discrete band edge states associated with O-atom vacancies pinned and clustered at grain boundaries, whereas in as-deposited films, and films with a physical thickness of ~ 2 nm, they are band-tail defects with a density reduced by more than an order of magnitude. Defect states in non-crystalline high Si3N4 content Hf Si oxynitride alloys are qualitatively different than those in the either regime of nano-crystallinity, but instead are similar to those in SiO2, with densities < 1011 cm− 2 contrasted with defects densities in excess of 1011 cm− 2 in films with nano-grains ~ 2 nm, and extending to > 1012 cm− 2 in films with nano-grains > 3–4 nm. DA - 2008/11/3/ PY - 2008/11/3/ DO - 10.1016/j.tsf.2008.08.098 VL - 517 IS - 1 SP - 437-440 SN - 0040-6090 KW - Thin film high-k dielectrics KW - Non-crystalline transition metal oxides KW - Nano-crystalline transition metal oxides KW - Bulk defects KW - Intrinsic bonding defects KW - Divacancies ER - TY - CONF TI - Stress rupture characteristics of zirconium alloy cladding under closed-end internal pressurization AU - Marple, B. AU - Song, Y. J. AU - Gollapudi, S. AU - Murty, K. L. AU - Charit, I. AB - An understanding of stress rupture behavior of zirconium alloy cladding tubes is of paramount importance for applications in nuclear reactors. Stress rupture properties of recrystallized Zircaloy-4 alloy were evaluated using burst testing of closed-end thin-walled tubing at varied test temperatures and internal pressures. The rupture data are correlated using the Larson-Miller parameter. The uniform circumferential elongations were also measured from which the hoop creep rates were calculated. These results were fitted to Monkman-Grant relationship with the aim of extrapolating the data to in-service stress levels. Furthermore, the creep data were plotted according to the Dorn equation where a transition in deformation mechanism from ‘power-law’ to ‘power law breakdown’ for Zircaloy-4 was noted. TEM studies corroborated the transition in mechanism from the power-law regime to a power-law breakdown regime. C2 - 2008/// C3 - Proceedings of 16th International Conference on Nuclear Engineering-Volume 1 DA - 2008/// DO - 10.1115/icone16-48006 SP - 385-388 PB - New York, NY: ASME SN - 9780791848142 ER - TY - JOUR TI - Molecular Simulation of the Influence of Interface Faceting on the Shock Sensitivity of a Model Plastic Bonded Explosive AU - Shi, Yunfeng AU - Brenner, Donald W. T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - Molecular dynamics simulations are used to model the shock loading of an interface with various degrees of nanometer scale faceting between an inert binder and an energetic crystal. The facets create regions of local compression that induce exothermic reaction that leads to local hotspots and an increased shock sensitivity to detonation. Two mechanisms for compression and hotspot formation are identified that depend on the shock impedance mismatch between the binder and energetic crystal, namely shock focusing and local compression of the facets. These results provide a possible explanation for why spherical RDX crystals in cast polymer-bonded explosives appear less shock sensitive than RDX with more faceted morphologies. DA - 2008/11/27/ PY - 2008/11/27/ DO - 10.1021/jp805690w VL - 112 IS - 47 SP - 14898-14904 SN - 1520-6106 ER - TY - JOUR TI - Deep-level transient spectroscopy study on direct silicon bonded (110)/(100) interfacial grain boundary AU - Yu, X. G. AU - Lu, J. G. AU - Rozgonyi, G. T2 - Semiconductor Science and Technology DA - 2008/// PY - 2008/// VL - 23 IS - 12 ER - TY - JOUR TI - Composite Carbon Nanotube/Silica Fibers with Improved Mechanical Strengths and Electrical Conductivities AU - Peng, Huisheng AU - Jain, Menka AU - Peterson, Dean E. AU - Zhu, Yuntian AU - Jia, Quanxi T2 - SMALL AB - Two approaches to the synthesis of composite carbon nanotube/silica fibers in which the carbon nanotubes are highly aligned are investigated, one involving directly casting and the other using surface modification to induce hydrogen bonding between the carbon nanotubes and a silica precursor. Due to the nanotube alignment, these composites (see image) exhibit high strength and conductivity, and good chemical and thermal stability, and are expected to find applications in many advanced applications. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2008/11// PY - 2008/11// DO - 10.1002/smll.200800231 VL - 4 IS - 11 SP - 1964-1967 SN - 1613-6829 KW - carbon nanotubes KW - composite fibers KW - hydrogen bonding KW - silica ER - TY - JOUR TI - Thickness inhomogenities in the organometallic chemical vapor deposition of GaP AU - Liu, X. AU - Aspnes, D. E. T2 - APPLIED PHYSICS LETTERS AB - We analyze exponential lateral-thickness variations observed in the growth of GaP on (001) GaAs, thermally generated SiO2, (001) Si, and nanoscopically roughened Si surfaces by organometallic chemical vapor deposition, using as a reference the polycrystalline GaP deposited on the Mo susceptor surrounding the 2in. wafers. We find these variations to be due to differences in the chemical reactivities of the various surfaces toward the generation of a precursor, probably a H–P=Ga–CH3 dimer adduct, by heterogeneous catalysis followed by desorption and diffusion through the gas phase. DA - 2008/11/17/ PY - 2008/11/17/ DO - 10.1063/1.3029742 VL - 93 IS - 20 SP - SN - 0003-6951 KW - catalysis KW - desorption KW - diffusion KW - gallium compounds KW - III-V semiconductors KW - MOCVD KW - semiconductor growth KW - semiconductor thin films ER - TY - JOUR TI - Thickness dependence of submicron thick Pb(Zr0.3Ti0.7)O-3 films on piezoelectric properties AU - Kim, Dong-Joo AU - Park, Jung-Hyun AU - Shen, Dongna AU - Lee, Joo Won AU - Kingon, Angus I. AU - Yoon, Young Soo AU - Kim, Seung-Hyun T2 - CERAMICS INTERNATIONAL AB - The effects of thickness on the piezoelectric and electric properties of tetragonal composition, polycrystalline, (1 1 1)-textured Pb(Zr0.3Ti0.7)O3 films are investigated. The effective piezoelectric coefficient d33 is characterized by a double-beam laser interferometer and is measured to increase with film thickness although extrinsic contribution such as 90° domain wall motion is negligible from the nonlinearity of piezoelectric coefficient. Constituent parameters to affect piezoelectric coefficient such as polarization and dielectric properties were analyzed based on the semiempirical phenomenological equation. The effectiveness of poling was also evaluated as a function of film thickness. These results present that the increase of effective d33 in these tetragonal PZT films can be mainly due to enhanced intrinsic contributions. DA - 2008/12// PY - 2008/12// DO - 10.1016/j.ceramint.2007.07.016 VL - 34 IS - 8 SP - 1909-1915 SN - 0272-8842 KW - A. Sol-gel processes KW - C. Piezoelectric properties KW - D. PZT ER - TY - JOUR TI - Suppression of defect states in HfSiON gate dielectric films on n-type Ge(100) substrates AU - Chung, K. B. AU - Seo, H. AU - Long, J. P. AU - Lucovsky, G. T2 - APPLIED PHYSICS LETTERS AB - Defect states in HfO2 and HfSiON films deposited on Ge(100) substrates were studied by spectroscopic ellipsometry (SE) and x-ray absorption spectroscopy (XAS). In addition, structural and compositional changes in these films were examined via medium energy ion scattering (MEIS). SE and XAS experiments revealed two distinct band edge defect states, located at 1.7±0.1eV and at 2.7±0.1 below the conduction band edges of these films. The number of defect states in HfO2 increased noticeably following postdeposition annealing (PDA), whereas in HfSiON, it showed only small increases following the same treatment. MEIS measurements showed that Ge diffusion into HfO2 films was enhanced significantly by PDA as well; however, this effect was less pronounced in the HfSiON films. The suppression of defect state enhancement in HfSiON films was correlated with lower levels of Ge diffusion and increased structural stability with respect to HfO2. DA - 2008/11/3/ PY - 2008/11/3/ DO - 10.1063/1.3005422 VL - 93 IS - 18 SP - SN - 0003-6951 KW - annealing KW - conduction bands KW - defect states KW - diffusion KW - ellipsometry KW - germanium KW - hafnium compounds KW - high-k dielectric thin films KW - ion-surface impact KW - X-ray absorption spectra ER - TY - JOUR TI - Nanoparticle-regulated phase behavior of ordered block copolymers AU - Gaines, Michelle K. AU - Smith, Steven D. AU - Samseth, Jon AU - Bockstaller, Michael R. AU - Thompson, Russell B. AU - Rasmussen, Kim O. AU - Spontak, Richard J. T2 - SOFT MATTER AB - Although block copolymer motifs have received considerable attention as supramolecular templates for inorganic nanoparticles, experimental observations of a nanostructured diblock copolymer containing inorganic nanoparticles—supported by theoretical trends predicted from a hybrid self-consistent field/density functional theory—confirm that nanoparticle size and selectivity can likewise stabilize the copolymer nanostructure by increasing its order–disorder transition temperature. DA - 2008/// PY - 2008/// DO - 10.1039/b805540h VL - 4 IS - 8 SP - 1609-1612 SN - 1744-6848 ER - TY - JOUR TI - Berreman effect in infrared absorption spectroscopy of ionic oxide coatings formed by atomic layer deposition on three-dimensional structures AU - Scarel, Giovanna AU - Hyde, G. Kevin AU - Hojo, Daisuke AU - Parsons, Gregory N. T2 - JOURNAL OF APPLIED PHYSICS AB - We show through modeling and experimentation that the Berreman effect, physically manifested and investigated on planar surfaces for more than four decades, can be readily realized and studied in three-dimensional nonplanar structures. The Berreman effect is also used as a nonlocal probe to evaluate topography and homogeneity of insulating ionic oxide layers in nonplanar geometries. During infrared transmission studies the macroscopic angular dependence of the longitudinal optical mode absorbance deviates from that observed in the planar case, and the angular dependence is shown to be physically linked to geometry and homogeneity of the ionic oxide layer. Spectroscopic modeling confirms the observations on the angular dependence of longitudinal optical mode absorbance on various nonplanar systems. A linear combination of [sin(θ)]4 with appropriate coefficients is found to describe the trend of longitudinal optical mode absorbance in nonplanar structures. DA - 2008/11/1/ PY - 2008/11/1/ DO - 10.1063/1.3013439 VL - 104 IS - 9 SP - SN - 1089-7550 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000260941700110&KeyUID=WOS:000260941700110 ER - TY - JOUR TI - Analysis of interface layers by spectroscopic ellipsometry AU - Kim, T. J. AU - Yoon, J. J. AU - Kim, Y. D. AU - Aspnes, D. E. AU - Klein, M. V. AU - Ko, D. -S. AU - Kim, Y. -W. AU - Elarde, V. C. AU - Coleman, J. J. T2 - APPLIED SURFACE SCIENCE AB - Abstract We investigate the relative validity of the Bruggeman effective-medium approximation and several alloy models to describe interfaces in the analysis of spectroscopic ellipsometric data of laminar samples, using data obtained on an Al x Ga 1− x As multilayer sample fabricated specifically for this purpose. The investigation highlights the types of errors that result from the use of inappropriate models. Optimum results are obtained with the alloy model where the graded-composition regions are approximated with multilayer stacks. DA - 2008/11/30/ PY - 2008/11/30/ DO - 10.1016/j.apsusc.2008.07.005 VL - 255 IS - 3 SP - 640-642 SN - 1873-5584 KW - AlGaAs KW - Ellipsometry KW - Multilayer ER - TY - JOUR TI - Influence of Pb segregation on the deformation of nanocrystalline Al: Insights from molecular simulations AU - Jang, S. AU - Purohit, Y. AU - Irving, D. L. AU - Padgett, C. AU - Brenner, D. AU - Scattergood, R. O. T2 - ACTA MATERIALIA AB - Molecular dynamics straining simulations using a two-dimensional columnar model were run for pure Al with grain sizes from 5 to 30 nm, and for 10 nm grain size Al–Pb alloys containing 1, 2 and 3 at.% Pb. Monte Carlo simulations showed that all the Pb atoms segregate to the grain boundaries. Pb segregation suppresses the nucleation of partial dislocations and twins during straining. At 3 at.% Pb, no dislocations or twins are observed throughout the straining history. It also appeared that Pb tends to segregate to the same locations in grain boundaries that were favorable for partial dislocation emission. Grain boundaries with Pb segregates were very robust against dissociation during straining compared to pure Al. The yield stress determined from stress–strain curves showed a decrease with increasing Pb content, supporting a similar observation for the hardness change measured on nanocrystalline Al–Pb alloys. DA - 2008/10// PY - 2008/10// DO - 10.1016/j.actamat.2008.05.024 VL - 56 IS - 17 SP - 4750-4761 SN - 1359-6454 KW - MD simulations KW - MC simulations KW - Al-Pb alloys KW - Nanocrystalline materials KW - Plastic deformation ER - TY - JOUR TI - Grain size distribution in ultrafine-grained yttria-stabilized zirconia deformed without and with an electric field AU - Starnes, Stephen AU - Conrad, Hans T2 - SCRIPTA MATERIALIA AB - Grain size distributions were determined in the grip ( e  ≈ 0) and near fracture ( e  ≈ 1.0) of yttria-stabilized zirconia ( d ¯ 0 = 0.44  μm) specimens deformed in tension at 1450–1600 °C without and with an electric field. The mean grain size increased with temperature, but decreased with field, with no clear effect of strain. The distributions for all test conditions fit a single curve based on the Bitti–Nunzio model, showing that the field had no significant effect on the grain size distribution. DA - 2008/11// PY - 2008/11// DO - 10.1016/j.scriptamat.2008.07.025 VL - 59 IS - 10 SP - 1115-1118 SN - 1359-6462 KW - Grain size KW - Electric field KW - Zirconia KW - Strain ER - TY - JOUR TI - Field-driven surface segregation of biofunctional species on electrospun PMMA/PEO microfibers AU - Sun, Xiao-Yu AU - Nobles, Larrisha R. AU - Boerner, Hans G. AU - Spontak, Richard J. T2 - MACROMOLECULAR RAPID COMMUNICATIONS AB - Abstract The need to biofunctionalize polymer surfaces for targeted bio‐related applications continues to grow, and efforts designed to meet this need rely heavily on surface grafting or polymerization. In this study, we provide a viable alternative by demonstrating that the peptide segment of a polymer‐peptide conjugate can be selectively driven to the surface of polymer nano/microfibers during electrospinning due to contrast in polarizability. Judicious choice of the polymer sequence in the conjugate permits use of the conjugate with compatible fiber‐forming polymers. Here, we use a water soluble poly(ethylene oxide)‐containing conjugate in combination with a hydrophobic thermoplastic, poly(methyl methacrylate). Surface enrichment is measured by X‐ray photoelectron spectroscopy, and fiber morphology is investigated by electron microscopy. Microfibers generated from the blends examined here are largely resistant to long term water immersion and are thus suited as support scaffolds or filtration membranes. magnified image DA - 2008/9/1/ PY - 2008/9/1/ DO - 10.1002/marc.200800163 VL - 29 IS - 17 SP - 1455-1460 SN - 1521-3927 KW - fibers KW - functionalization of polymers KW - peptides KW - surfaces KW - toughness ER - TY - JOUR TI - Extended chemical crosslinking of a thermoplastic polyimide: Macroscopic and microscopic property development AU - Aberg, Christopher M. AU - Ozcam, Ali E. AU - Majikes, Jacob M. AU - Seyam, Mohamed A. AU - Spontak, Richard J. T2 - MACROMOLECULAR RAPID COMMUNICATIONS AB - Abstract Polyimides are well established as gas separation membranes due to their intrinsically low free volume and correspondingly high H 2 selectivity relative to other gases such as CO 2 . Prior studies have established that H 2 /CO 2 selectivity can be improved by crosslinking polyimides with diamines differing in spacer length. In this work, we follow the evolution of macroscopic and microscopic properties of a commercial polyimide over long crosslinking times ( t x ) with 1,3‐diaminopropane. According to spectroscopic analysis, the crosslinking reaction saturates after ≈24 h, whereas tensile, nanoindentation and stress relaxation tests reveal that the material stiffens, and possesses a long relaxation time that increases with increasing t x . Although differential scanning calorimetry shows that the glass transition temperature decreases systematically with increasing t x , permeation studies indicate that the permeabilities of H 2 and CO 2 decrease, while the H 2 /CO 2 selectivity increases markedly, with increasing t x . At long t x , the polyimide becomes impermeable to CO 2 , suggesting that it could be used as a barrier material. magnified image DA - 2008/9/1/ PY - 2008/9/1/ DO - 10.1002/marc.200800230 VL - 29 IS - 17 SP - 1461-1466 SN - 1022-1336 KW - barrier KW - calorimetry KW - crosslinking KW - networks KW - polyimides ER - TY - JOUR TI - Autophobicity-driven surface segregation and patterning of core-shell microgel nanoparticles AU - Wei, Bin AU - Gurr, Paul A. AU - Gozen, Arif O. AU - Blencowe, Anton AU - Solomon, David H. AU - Qiao, Greg G. AU - Spontak, Richard J. AU - Genzer, Jan T2 - NANO LETTERS AB - Core−shell microgel (CSMG) nanoparticles, also referred to as core-cross-linked star (CCS) polymers, can be envisaged as permanently cross-linked block copolymer micelles and, as such, afford novel opportunities for chemical functionalization, templating, and encapsulation. In this study, we explore the behavior of CSMG nanoparticles comprising a poly(methyl methacrylate) (PMMA) shell in molten PMMA thin films. Because of the autophobicity between the densely packed, short PMMA arms of the CSMG shell and the long PMMA chains in the matrix, the nanoparticles migrate to the film surface. They cannot, however, break through the surface because of the inherently high surface energy of PMMA. Similar thermal treatment of CSMG-containing PMMA thin films with a polystyrene (PS) capping layer replaces surface energy at the PMMA/air interface by interfacial energy at the PMMA/PS interface, which reduces the energy barrier by an order of magnitude, thereby permitting the nanoparticles to emerge out of the PMMA bulk. This nanoscale process is reversible and can be captured at intermediate degrees of completion. Moreover, it is fundamentally general and can be exploited as an alternative means by which to reversibly pattern or functionalize polymer surfaces for applications requiring responsive nanolithography. DA - 2008/9// PY - 2008/9// DO - 10.1021/nl802109x VL - 8 IS - 9 SP - 3010-3016 SN - 1530-6992 ER - TY - JOUR TI - Strengthening mechanisms in nanocrystalline alloys AU - Scattergood, R. O. AU - Koch, C. C. AU - Murty, K. L. AU - Brenner, D. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - The mechanisms for strengthening nanocrystalline metals by alloy additions are reviewed and a new model for nano-particle strengthening by Orowan bypassing in nano-grains is proposed. Recent experimental results for three different nanocrystalline alloy systems, Fe–Pb, Fe–Al2O3 and Al–Pb are presented and analyzed in terms of non-equilibrium solid solution strengthening, nano-composite strengthening and Orowan particle strengthening, respectively. Conflicting alloy hardening and softening effects observed in Al–Pb appear to be the result of interplay between Orowan particle hardening and a softening mechanism due to grain-boundary segregation. Preliminary MD simulations support the latter suggestion. DA - 2008/10/15/ PY - 2008/10/15/ DO - 10.1016/j.msea.2007.04.132 VL - 493 IS - 1-2 SP - 3-11 SN - 0921-5093 KW - nanocrystalline alloys KW - strengthening mechanisms KW - Orowan model ER - TY - JOUR TI - Molecular dynamics simulations of deformation in nanocrystalline Al-Pb alloys AU - Jang, S. AU - Purohit, Y. AU - Irving, D. AU - Padgett, C. AU - Brenner, D. AU - Scattergood, R. O. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Abstract A modified embedded-atom method (MEAM) potential was developed and used for molecular dynamics (MD) straining simulations of Al–Pb alloys with a grain size of 10 nm and Pb content up to 3 at.%. Monte Carlo (MC) simulations done at 300 K indicated that all the Pb is segregated to the grain boundaries in these alloys. As the Pb content increases, partial dislocation nucleation at grain boundaries is suppressed, and the plastic strain is accommodated by mechanisms other than dislocation slip. The increasing Pb content was accompanied by a reduction in the yield and peak stress values. DA - 2008/10/15/ PY - 2008/10/15/ DO - 10.1016/j.msea.2007.05.130 VL - 493 IS - 1-2 SP - 53-57 SN - 0921-5093 KW - MD straining simulation KW - Al-Pb alloys KW - grain boundary segregation ER - TY - JOUR TI - Mechanical and biological properties of nanoporous carbon membranes AU - Narayan, Roger J. AU - Aggarwal, Ravi AU - Wei, Wei AU - Jin, Chunming AU - Monteiro-Riviere, Nancy A. AU - Crombez, Rene AU - Shen, Weidian T2 - BIOMEDICAL MATERIALS AB - Implantable blood glucose sensors have inadequate membrane–tissue interfaces for long term use. Biofouling and inflammation processes restrict biosensor membrane stability. An ideal biosensor membrane material must prevent protein adsorption and exhibit cell compatibility. In addition, a membrane must exhibit high porosity and low thickness in order to allow the biosensor to respond to analyte fluctuations. In this study, the structural, mechanical and biological properties of nanoporous alumina membranes coated with diamond-like carbon thin films were examined using scanning probe microscopy, nanoindentation and MTT viability assay. We anticipate that this novel membrane material could find use in immunoisolation devices, kidney dialysis membranes and other medical devices encountering biocompatibility issues that limit in vivo function. DA - 2008/9// PY - 2008/9// DO - 10.1088/1748-6041/3/3/034107 VL - 3 IS - 3 SP - SN - 1748-605X ER - TY - JOUR TI - Mechanical Behavior of Nanostructured Materials, in Honor of Carl Koch held at TMS 2007, Orlando, Florida Preface AU - Zhang, Xinghang AU - Kostorz, Gernot AU - Liu, Chain T. AU - Rigsbee, Mike AU - Suryanarayana, C. AU - Wang, Haiyan AU - Zhu, Yuntian AU - Zhang, Deliang T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING DA - 2008/10/15/ PY - 2008/10/15/ DO - 10.1016/j.msea.2008.01.019 VL - 493 IS - 1-2 SP - 1-2 SN - 0921-5093 ER - TY - JOUR TI - Ion beam pretreatment of polymeric substrates for ITO thin film deposition AU - Cho, Jun-Sik AU - Han, Younggun AU - Cuomo, Jerome J. T2 - SOLID STATE SCIENCES AB - Polycarbonate (PC) surfaces were pretreated by an 1 keV Ar+ ion irradiation in oxygen environment to improve surface properties before depositing indium tin oxide (ITO) films. The hydrophobic PC surfaces were converted into more hydrophilic ones after a surface modification. Improved wettability of the treated PC surfaces was due to the formation of new polar groups on the surfaces, responsible for the increase of polar component in the surface energy. Chemical interaction between unstable chains induced by energetic ion bombardment and oxygen gas resulted in the formation of the polar groups, which were identified as oxygen containing carbon bonds such as carbonyl by the XPS study. In the initial growth stage of the ITO films on the PC substrates, the newly formed polar groups prevented hill-locks from growing on the surfaces, which contributed to the improvement of thermal stability in the ITO thin films on the modified PC substrates. The Ar+ ion irradiation in oxygen environment also led to a significant adhesion enhancement of PC substrates to ITO films which was explained in terms of the physical and chemical changes on the PC surfaces. DA - 2008/7// PY - 2008/7// DO - 10.1016/j.solidstatesciences.2007.11.010 VL - 10 IS - 7 SP - 941-949 SN - 1873-3085 KW - ion irradiation KW - wettability KW - polar group KW - adhesion KW - indium tin oxide ER - TY - JOUR TI - High strength and high ductility in a nanoscale superlattice of Ni-2(Cr,Mo) deformable by twinning AU - Tawancy, H. M. AU - Aboelfotoh, M. O. T2 - SCRIPTA MATERIALIA AB - It is demonstrated that long-range ordering can be utilized to synthesize a nanoscale superlattice of Ni2(Cr,Mo) in a Ni–18.6 at.% Mo–15.1 at.% Cr. The superlattice is distinguished by high strength and high ductility. This behavior has been correlated with the crystallography of the disorder–order transformation, which favors deformation by twinning on the {1 1 1} planes of the parent face-centered cubic structure. DA - 2008/10// PY - 2008/10// DO - 10.1016/j.scriptamat.2008.06.026 VL - 59 IS - 8 SP - 846-849 SN - 1359-6462 KW - aging KW - nanocrystalline materials KW - nickel alloys KW - tension test KW - transmission electron microscopy ER - TY - CONF TI - Epitaxial growth of high-kappa dielectrics for GaN MOSFETs AU - Jur, J. S. AU - Wheeler, G. D. AU - Veety, M. T. AU - Lichtenwalner, D. J. AU - Barlage, D. W. AU - Johnson, M. A. L. C2 - 2008/// C3 - Advances in gan, gaas, sic and related alloys on silicon substrates DA - 2008/// DO - 10.1557/proc-1068-c08-02 VL - 1068 SP - 63-68 ER - TY - JOUR TI - Elimination of GeO2 and Ge3N4 interfacial transition regions and defects at n-type Ge interfaces: A pathway for formation of n-MOS devices on Ge substrates AU - Lucovsky, G. AU - Lee, S. AU - Long, J. P. AU - Seo, H. AU - Luning, J. T2 - Applied Surface Science AB - The contribution from relatively low-K SiON interfacial transition regions (ITRs) between Si and transition metal (TM) gate dielectrics places a significant limitation on equivalent oxide thickness (EOT) scaling for Si complementary metal-oxide-semiconductor (CMOS) devices. This limitation is equally significant and limiting for Ge CMOS devices. Low-K Ge-based ITRs in Ge devices have also been shown to limit performance and reliability, particular for n-MOS field effect transistors. This article identifies the source of significant electron trapping at interfaces between n-Ge or inverted p-Ge, and Ge oxide, nitride and oxynitride ITRs. This is shown to be an interfacial band alignment issue in which native Ge ITRs have conduction band offset energies smaller than those of TM dielectrics, and trap electrons for negative Ge substrate bias. This article also describes a novel remote plasma processing approach for effectively eliminating any significant native Ge ITRs and using a plasma-processing/annealing process sequence for bonding TM gate dielectrics directly to the Ge substrate surface. DA - 2008/// PY - 2008/// DO - 10.1016/j.apsusc.2008.03.157 VL - 254 IS - 23 SP - 7933-7937 ER - TY - JOUR TI - Different optical absorption edges in AlN bulk crystals grown in m- and c-orientations AU - Lu, P. AU - Collazo, R. AU - Dalmau, R. F. AU - Durkaya, G. AU - Dietz, N. AU - Sitar, Z. T2 - APPLIED PHYSICS LETTERS AB - AlN single crystals were grown on m-plane (101¯0) and c-plane (0001¯) AlN seeds under identical growth conditions. The m-plane AlN crystals exhibited substantially lower oxygen incorporation, ∼1018cm−3, than the c-plane crystals, ∼1019cm−3. By investigating optical transmission spectra, m-plane AlN had absorption bands at 4.05 and 4.35eV, while c-plane AlN had an absorption band edge at 4.85eV. These below bandgap absorption bands strongly correlate with the reported transitions related to Al vacancy-impurity complexes, such as the complex of an Al vacancy and two oxygen atoms, (VAl–2ON)1− and the complex of an Al vacancy and one oxygen atom, (VAl–ON)2−, becoming the major cause for the poor, below bandgap optical transparency (α&gt;200cm−1) of these crystals. DA - 2008/9/29/ PY - 2008/9/29/ DO - 10.1063/1.2996413 VL - 93 IS - 13 SP - SN - 1077-3118 ER - TY - CONF TI - Determining the optimal stacking fault energy for achieving high ductility in ultrafine-grained Cu-Zn alloys AU - Zhao, Y. H. AU - Liao, X. Z. AU - Horita, Z. AU - Langdon, T. G. AU - Zhu, Y. T. C2 - 2008/// C3 - Materials Science & Engineering. A, Structural Materials: Properties, Microstructure and Processing DA - 2008/// VL - 493 SP - 123-129 M1 - 1-2 ER - TY - JOUR TI - Detailed arsenic concentration profiles at Si/SiO2 interfaces AU - Pei, L. AU - Duscher, G. AU - Steen, C. AU - Pichler, P. AU - Ssel, H. R. AU - Napolitani, E. AU - De Salvador, D. AU - Piro, A. M. AU - Terrasi, A. T. AU - Severac, F. AU - Cristiano, F. AU - Ravichandran, K. AU - Gupta, N. AU - Windl, W. T2 - Journal of Applied Physics DA - 2008/// PY - 2008/// VL - 104 IS - 4 ER - TY - JOUR TI - Deformation twinning in bulk nanocrystalline metals: Experimental observations AU - Zhu, Y. T. AU - Liao, X. Z. AU - Wu, X. L. T2 - JOM AB - Deformation twins have been observed in nanocrystalline (nc) fcc metals with medium-to-high stacking fault energies such as aluminum, copper, and nickel. These metals in their coarse-grained states rarely deform by twining at room temperature and low strain rates. Several twinning mechanisms have been reported that are unique to nc metals. This paper reviews experimental evidences on deformation twinning and partial dislocation emissions from grain boundaries, twinning mechanisms, and twins with zero-macro-strain. Factors that affect the twinning propensity and recent analytical models on the critical grain sizes for twinning are also discussed. The current issues on deformation twinning in nanocrystalline metals are listed. DA - 2008/9// PY - 2008/9// DO - 10.1007/s11837-008-0120-1 VL - 60 IS - 9 SP - 60-64 SN - 1543-1851 ER - TY - JOUR TI - Defect dependent ferromagnetism in MgO doped with Ni and Co AU - Narayan, J. AU - Nori, Sudhakar AU - Pandya, D. K. AU - Avasthi, D. K. AU - Smirnov, A. I. T2 - Applied Physics Letters AB - We have investigated magnetic properties of MgO single crystals doped with Ni and Co impurities, and studied changes in magnetic properties after heavy ion irradiation. These results are compared with doped single-crystal thin films that contain a higher concentration of trapped defects. The as-grown bulk single crystals, which contain a small equilibrium concentration of vacancies, exhibit a perfect paramagnetic behavior throughout the temperature range and magnetic field. By introducing defects either by ion irradiation or by thin film deposition, which have trapped defects, we are able to achieve defect-mediated ferromagnetic ordering. DA - 2008/8/25/ PY - 2008/8/25/ DO - 10.1063/1.2977614 VL - 93 IS - 8 SP - 082507 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2977614 DB - Crossref ER - TY - JOUR TI - Atomistic modeling of the segregation of lead impurities to a grain boundary in an aluminum bicrystalline solid AU - Purohit, Y. AU - Jang, S. AU - Irving, D. L. AU - Padgett, C. W. AU - Scattergood, R. O. AU - Brenner, D. W. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Using Monte Carlo simulations, new insights into the atomic segregation of lead (Pb) impurities to a Σ5 〈1 0 0〉 {2 1 0} tilt aluminum (Al) grain boundary have been obtained. Interatomic interactions in the Al–Pb alloy system were described using a modified embedded atom method potential with parameters that fit to the results of density functional calculations. The simulations predict segregation of Pb impurities along the Al grain boundary prior to the formation of Pb clusters. Analyses of grain boundary energies for varying concentrations of Pb suggests that grain boundaries in Al can be thermodynamically stabilized by Pb impurities with respect to a dilute solid solution of Pb in Al. DA - 2008/10/15/ PY - 2008/10/15/ DO - 10.1016/j.msea.2007.05.128 VL - 493 IS - 1-2 SP - 97-100 SN - 1873-4936 KW - bicrystal KW - Monte Carlo KW - segregation KW - grain boundary energy KW - grain growth ER - TY - JOUR TI - Grain growth behaviour and consolidation of ball-milled nanocrystalline Fe-10Cr alloy AU - Gupta, Rajeev AU - Raman, R. K. Singh AU - Koch, Carl C. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Nanocrystalline iron–chromium alloys may provide considerable corrosion resistance, even at low chromium contents. However, processing of such alloys could be a challenge. This paper describes successful synthesis of nanocrystalline Fe–10%Cr alloy by ball-milling route. In the absence of suitable hot compaction facility, the alloy powder could be successfully compacted close to the desired density, by employing a step of prior annealing of the powder. Grain growth behaviour of Fe–10%Cr nanocrystalline alloy was investigated at 500, 600 and 700 °C. At 500 °C, no appreciable grain growth was observed, after the initial grain growth. However, sudden and rapid grain growth was observed after 90 min at 600 °C, and 30 min at 700 °C. DA - 2008/10/25/ PY - 2008/10/25/ DO - 10.1016/j.msea.2008.04.019 VL - 494 IS - 1-2 SP - 253-256 SN - 0921-5093 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-49849092043&partnerID=MN8TOARS KW - Nanocrystalline Fe-Cr alloys KW - Ball milling KW - Grain growth ER - TY - JOUR TI - Effect of strained-Si layer thickness on dislocation distribution and SiGe relaxation in strained-Si/SiGe heterostructures AU - Lu, J. G. AU - Rozgonyi, G. AU - Seacrist, M. AU - Chaumont, M. AU - Campion, A. T2 - Journal of Applied Physics DA - 2008/// PY - 2008/// VL - 104 IS - 7 ER - TY - JOUR TI - Vortex ferroelectric domains AU - Gruverman, A. AU - Wu, D. AU - Fan, H. J. AU - Vrejoiu, I. AU - Alexe, M. AU - Harrison, R. J. AU - Scott, J. F. T2 - Journal of Physics. Condensed Matter DA - 2008/// PY - 2008/// VL - 20 IS - 34 ER - TY - JOUR TI - Strong and ductile colossal carbon tubes with walls of rectangular macropores AU - Peng, Huisheng AU - Chen, Daoyong AU - Huang, Jian-Yu AU - Chikkannanavar, S. B. AU - Haenisch, J. AU - Jain, Menka AU - Peterson, D. E. AU - Doorn, S. K. AU - Lu, Yunfeng AU - Zhu, Y. T. AU - Jia, Q. X. T2 - PHYSICAL REVIEW LETTERS AB - We report a new type of carbon material-porous colossal carbon tubes. Compared with carbon nanotubes, colossal carbon tubes have a much bigger size, with a diameter of between 40 and 100 mum and a length in the range of centimeters. Significantly, the walls of the colossal tubes are composed of macroscopic rectangular columnar pores and exhibit an ultralow density comparable to that of carbon nanofoams. The porous walls of colossal tubes also show a highly ordered lamellar structure similar to that of graphite. Furthermore, colossal tubes possess excellent mechanical and electrical properties. DA - 2008/10/3/ PY - 2008/10/3/ DO - 10.1103/physrevlett.101.145501 VL - 101 IS - 14 SP - SN - 1079-7114 ER - TY - JOUR TI - Photoluminescence-enhanced biocompatible quantum dots by phospholipid functionalization AU - Shi, Yunfeng AU - He, Peng AU - Zhu, Xinyuan T2 - MATERIALS RESEARCH BULLETIN AB - A simple two-step strategy using phospholipid (PPL) to functionalize core/shell CdSe/ZnS quantum dots (QDs) has been described. The experimental data show that the use of S–H terminated PPL results not only in the high colloidal stability of core/shell CdSe/ZnS QDs in the aqueous phase, but also in the significant enhancement of photoluminescence. The degree of the enhancement is a function of the PPL–CdSe/ZnS QDs sample concentration. These results might be promising for future biological platform in new devices ranging from photovoltaic cells to biosensors and other devices. DA - 2008/10/2/ PY - 2008/10/2/ DO - 10.1016/j.materresbull.2007.10.034 VL - 43 IS - 10 SP - 2626-2635 SN - 1873-4227 KW - nanostructures KW - surfaces KW - chemical synthesis ER - TY - JOUR TI - Nanodomain faceting in ferroelectrics AU - Scott, J. F. AU - Gruverman, A. AU - Wu, D. AU - Vrejoiu, I. AU - Alexe, M. T2 - Journal of Physics. Condensed Matter DA - 2008/// PY - 2008/// VL - 20 IS - 42 ER - TY - JOUR TI - Triblock copolymer organogels as high-performance dielectric elastomers AU - Shankar, Ravi AU - Krishnan, Arjun K. AU - Ghosh, Tushar K. AU - Spontak, Richard J. T2 - MACROMOLECULES AB - Block copolymers and nanostructured materials derived therefrom are becoming increasingly ubiquitous in a wide variety of (nano)technologies. Recently, we have demonstrated that triblock copolymer organogels composed of physically cross-linked copolymer networks swollen with a midblock-selective solvent exhibit excellent electromechanical behavior as dielectric elastomers. In-plane actuation of such organogels, collectively referred to as electroactive nanostructured polymers (ENPs) to reflect the existence of a self-organized copolymer morphology, is attributed to the development of an electric-field-induced surface-normal Maxwell stress. In this study, we examine the composition and molecular weight dependence of the electromechanical properties afforded by organogels prepared from poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) triblock copolymers selectively swollen with EB-compatible aliphatic oligomers. These materials undergo ultrahigh actuation displacement at significantly reduced electric fields relative to previously reported dielectric elastomers and possess electromechanical coupling efficiencies, which relate the conversion from electrical input to mechanical output, greater than 90%. The design of ENPs with broadly tunable electromechanical properties represents an attractive route to responsive materials for advanced engineering, biomimetic and biomedical applications. DA - 2008/8/26/ PY - 2008/8/26/ DO - 10.1021/ma071903g VL - 41 IS - 16 SP - 6100-6109 SN - 1520-5835 ER - TY - JOUR TI - Single molecule measurements with photoelectron emission microscopy AU - Kong, Xianhua AU - Rowe, J. E. AU - Nemanich, R. J. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - In this research, variable wavelength photoelectron emission microscopy (PEEM) with tunable UV light from the Duke University free electron laser is applied to image single fibrinogen molecules adsorbed onto n-type silicon surfaces. High resolution PEEM images (∼10nm) are obtained with photon energies from 4to6eV. Wavelength-dependent image sequences are analyzed to determine the photoionization spectrum and the photoelectron emission threshold of individual molecules. The experimental data are fitted using temperature dependent Fowler law, square-root law, and cube-root law. The details of the theoretical models are discussed. The square-root and cube-root fittings reveal the ionization threshold of 5.0eV for fibrinogen adsorbed onto n-type silicon, while temperature dependent Fowler law shows a threshold of 4.9eV. The accuracy of the measurements is calculated to be ±0.2eV. The authors conclude that no significant difference is observed from the three theoretical fitting approaches. DA - 2008/7// PY - 2008/7// DO - 10.1116/1.2932094 VL - 26 IS - 4 SP - 1461-1465 SN - 2166-2746 ER - TY - JOUR TI - Properties of Ti-6Al-4V non-stochastic lattice structures fabricated via electron beam melting AU - Cansizoglu, O. AU - Harrysson, O. AU - Cormier, D. AU - West, H. AU - Mahale, T. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - This paper addresses foams which are known as non-stochastic foams, lattice structures, or repeating open cell structure foams. The paper reports on preliminary research involving the design and fabrication of non-stochastic Ti–6Al–4V alloy structures using the electron beam melting (EBM) process. Non-stochastic structures of different cell sizes and densities were investigated. The structures were tested in compression and bending, and the results were compared to results from finite element analysis simulations. It was shown that the build angle and the build orientation affect the properties of the lattice structures. The average compressive strength of the lattice structures with a 10% relative density was 10 MPa, the flexural modulus was 200 MPa and the strength to density ration was 17. All the specimens were fabricated on the EBM A2 machine using a melt speed of 180 mm/s and a beam current of 2 mA. Future applications and FEA modeling were discussed in the paper. DA - 2008/9/25/ PY - 2008/9/25/ DO - 10.1016/j.msea.2008.04.002 VL - 492 IS - 1-2 SP - 468-474 SN - 0921-5093 KW - non-stochastic foams KW - repeating open cell structures KW - Ti-6Al-4V KW - direct metal fabrication KW - layered manufacturing KW - rapid prototyping ER - TY - JOUR TI - Mechanical properties of bulk nanocrystalline aluminum-tungsten alloys AU - Rajulapati, K. V. AU - Scattergood, R. O. AU - Murty, K. L. AU - Horita, Z. AU - Langdon, T. G. AU - Koch, C. C. T2 - METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE DA - 2008/10// PY - 2008/10// DO - 10.1007/s11661-008-9593-3 VL - 39A IS - 10 SP - 2528-2534 SN - 1073-5623 ER - TY - JOUR TI - High tensile ductility and strength in bulk nanostructured nickel AU - Zhao, Y. H. AU - Topping, T. AU - Bingert, J. F. AU - Thornton, J. J. AU - Dangelewicz, A. M. AU - Li, Y. AU - Liu, W. AU - Zhu, Y. T. AU - Zhou, Y. Z. AU - Lavernia, E. L. AU - al., T2 - ADVANCED MATERIALS AB - Both high tensile ductility and high strength are achieved in bulk multimodal (Multi-Ni) and bimodal (Bi-Ni) nanostructured nickel, synthesized by cryomilling and subsequent quasi-isostatic forging processes. The relatively low tensile ductility of bulk nanostructured materials has been a major obstacle for their practical applications. This work provides a new approach for fabricating bulk nanostructured materials with both high ductility and strength. DA - 2008/8/18/ PY - 2008/8/18/ DO - 10.1002/adma.200800214 VL - 20 IS - 16 SP - 3028-3033 SN - 1521-4095 ER - TY - JOUR TI - Finite element modeling of 3D human mesenchymal stem cell-seeded collagen matrices exposed to tensile strain AU - Pfeiler, T. Wayne AU - Sumanasinghe, Ruwan D. AU - Loboa, Elizabeth G. T2 - JOURNAL OF BIOMECHANICS AB - The use of human mesenchymal stem cells (hMSCs) in tissue engineering is attractive due to their ability to extensively self-replicate and differentiate into a multitude of cell lineages. It has been experimentally established that hMSCs are influenced by chemical and mechanical signals. However, the combined chemical and mechanical in vitro culture conditions that lead to functional tissue require greater understanding. In this study, finite element models were created to evaluate the local loading conditions on bone marrow-derived hMSCs seeded in three-dimensional collagen matrices exposed to cyclic tensile strain. Mechanical property and geometry data used in the models were obtained experimentally from a previous study in our laboratory and from mechanical testing. Eight finite element models were created to simulate three-dimensional hMSC-seeded collagen matrices exposed to different levels of cyclic tensile strain (10% and 12%), culture media (complete growth and osteogenic differentiating), and durations of culture (7 and 14 days). Through finite element analysis, it was determined that globally applied uniaxial tensile strains of 10% and 12% resulted in local strains up to 18.3% and 21.8%, respectively. Model results were also compared to experimental studies in an attempt to explain observed differences between hMSC response to 10% and 12% cyclic tensile strain. DA - 2008/7/19/ PY - 2008/7/19/ DO - 10.1016/j.jbiomech.2008.04.007 VL - 41 IS - 10 SP - 2289-2296 SN - 1873-2380 KW - uniaxial tensile strain KW - HMSCs KW - collagen KW - bioreactor KW - finite element modeling ER - TY - JOUR TI - Reversible chemical phase separation in on-state of art ReWritable (RW) Ge2Sb2Te5 optical phase change memories AU - Lucovsky, Gerald AU - Phillips, James C. T2 - JOURNAL OF NON-CRYSTALLINE SOLIDS AB - Abstract Ge 2 Sb 2 Te 5 is one of the chalcogenide alloy materials of choice for ReWritable (RW) optical discs that are currently in manufacturing; however, there are many issues relating to the physics and chemistry underpinning the switching mechanism that have as yet to be resolved. This is paper identifies important relationships between the chemical bonding in the non-crystalline phase of Ge 2 Sb 2 Te 5 , and in the face-centered-cubic (FCC) nano-crystalline alloy phase that account for the markedly different optical and electrical properties that are enabling for memory applications. The non-crystalline material is characterized as an intermediate phase (IP) with minimal (i) bond-strain and (ii) extended macroscopic-strain, and includes a precursor bonding arrangement crucial to optical and electronic RW memories. The FCC phase has nano-crystallites trapped in a metastable diphasic composite that is stabilized by the inclusion of non-crystalline GeTe x ( x  ∼ 5) nano-clusters pinned at grain boundaries. DA - 2008/5/1/ PY - 2008/5/1/ DO - 10.1016/j.jnoncrysol.2007.09.059 VL - 354 IS - 19-25 SP - 2753-2756 SN - 0022-3093 KW - amorphous semiconductors KW - crystallization KW - synchrotron radiation KW - chalcogenides KW - laser-matter interactions KW - microcrystallinity KW - percolation KW - nano-clusters KW - nano-crystals KW - optical properties KW - reflectivity KW - defects KW - medium-range order KW - short-range order KW - glass transition ER - TY - JOUR TI - Low temperature metal oxide film deposition and reaction kinetics in supercritical carbon dioxide AU - Peng, Qing AU - Hojo, Daisuke AU - Park, Kie Jin AU - Parsons, Gregory N. T2 - THIN SOLID FILMS AB - An effective method is developed for low temperature metal oxide deposition through thermal decomposition of metal diketonates in supercritical carbon dioxide (scCO2) solvent. The rates of Al(acac)3 (Aluminum acetyl acetonate) and Ga(acac)3 (Gallium acetyl acetonate) thermal decomposition in scCO2 to form conformal Al2O3 and Ga2O3 thin films on planar surfaces were investigated. The thermal decomposition reaction of Al(acac)3 and Ga(acac)3 was found to be initialized at ∼ 150 °C and 160 °C respectively in scCO2 solvent, compared to ∼ 250 °C and 360 °C in analogous vacuum-based processes. By measuring the temperature dependence of the growth rates of metal oxide thin films, the apparent activation energy for the thermal decomposition of Al(acac)3 in scCO2 is found to be 68 ± 6 kJ/mol, in comparison with 80–100 kJ/mol observed for the corresponding vacuum-based thermal decomposition reaction. The enhanced thermal decomposition rate in scCO2 is ascribed to the high density solvent which effectively reduces the energy of the polar transition states in the reaction pathway. Preliminary results of thin film deposition of other metal oxides including ZrOx, FeOx, Co2O3, Cr2O3, HfOx from thermal decomposition of metal diketonates or fluorinated diketonates in scCO2 are also presented. DA - 2008/6/2/ PY - 2008/6/2/ DO - 10.1016/j.tsf.2007.10.057 VL - 516 IS - 15 SP - 4997-5003 SN - 0040-6090 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000256509100054&KeyUID=WOS:000256509100054 KW - supercritical carbon dioxide (scCO(2)) KW - metal oxides KW - solvation energy KW - thermal decomposition KW - metal diketonates ER - TY - JOUR TI - Length scale discontinuities between non-crystalline and nano-crystalline thin films: Chemical bonding self-organization, broken constraints and reductions of macroscopic strain AU - Lucovsky, G. AU - Phillips, J. C. T2 - Journal of Non-crystalline Solids DA - 2008/// PY - 2008/// DO - 10.1016/j.jnoncryso1.2007.09.044 VL - 354 IS - 19-25 SP - 2702-2705 ER - TY - JOUR TI - Improved epitaxy of barium titanate by molecular beam epitaxy through a single crystalline magnesium oxide template for integration on hexagonal silicon carbide AU - Goodrich, T. L. AU - Cai, Z. AU - Losego, M. D. AU - Maria, J. -P. AU - Kourkoutis, L. Fitting AU - Muller, D. A. AU - Ziemer, K. S. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Crystalline MgO(111) has the potential to be an effective template for the heteroepitaxial integration of BTO(111) and other functional oxides on 6H-SiC(0001). Deposition of MgO on 6H-SiC(0001) at 140°C resulted in a twinned structure with only (111) orientation. By heating the MgO(111) after deposition to 650°C at a background pressure of 1.0×10−9Torr or depositing the MgO at 650°C, the twinned structure can be minimized, resulting in a reflection high energy electron diffraction (RHEED) pattern characteristic of random epitaxial islands. The use of a 2nm MgO(111) template layer proved optimal for deposition of crystalline BTO(111) by molecular beam epitaxy on 6H-SiC(0001). The BTO was found to be twinned with a 60° in-plane rotation. The grain formation of the BTO resulted in a transmission dominated RHEED pattern. Deposition of BTO at a higher substrate temperature resulted in large grain formation, 50nm in size, but an increased surface roughness of 1.4±0.1nm over a 1μm2 area. In order to integrate BTO in a multiferroic device with multilayers of BTO(111) and hexagonal ferrites, it will be necessary to optimize the processing conditions to establish a smoother BTO surface for the subsequent heteroepitaxy of the magnetic film. DA - 2008/5// PY - 2008/5// DO - 10.1116/1.2889389 VL - 26 IS - 3 SP - 1110-1114 SN - 2166-2746 ER - TY - JOUR TI - Defect scaling in non-crystalline floppy/under-constrained and rigid/over-constrained thin films: Applications to a-Se, a-Si, and a-Si(H) AU - Lucovsky, Gerald AU - Kasap, Safa O. AU - Phillips, James C. T2 - JOURNAL OF NON-CRYSTALLINE SOLIDS AB - Bond constraint theory provides insights into glass and intermediate phase formation in covalently-bonded non-crystalline networks. Metrics are the average number of bonds/atom, Nav, and average number of bending and stretching constraints per atom, Cav. Cav is a linear function of Nav:Cav = 2.5Nav − 3, with ideal, low defect density glasses and thin films having values of Nav and Cav equal to 2.4, and 3.0, respectively. In over-constrained films, it has been argued and demonstrated experimentally, that the density of intrinsic defects is proportional to Nav − 2.4. In this paper we demonstrate that this scaling relationship, with the same empirical constants applies to floppy or under-constrained films with the example being a-Se where Nav has been determined from EXAFS studies and is ∼2.2. In addition we demonstrate that the density of defects in as deposited a-Si with a 6% density deficit, and broken bonding constraints, can be treated in the same way as spacing–filling over-constrained networks. DA - 2008/5/1/ PY - 2008/5/1/ DO - 10.1016/j.jnoncrysol.2007.09.048 VL - 354 IS - 19-25 SP - 2724-2727 SN - 1873-4812 KW - amorphous semiconductors KW - silicon KW - thin film transistors KW - nanocrystals KW - synchrotron radiation KW - UPS/XPS KW - glass transition KW - oxynitride glasses KW - chalcogenides KW - defects KW - nano-clusters KW - silica KW - medium-range order KW - short-range order ER - TY - JOUR TI - Bond constraint theory studies of chalcogenide phase change memories AU - Paesler, M. A. AU - Baker, D. A. AU - Lucovsky, G. T2 - Journal of Non-crystalline Solids DA - 2008/// PY - 2008/// DO - 10.1016/j.jnoncryso1.2007.09.045 VL - 354 IS - 19-25 SP - 2706-2710 ER - TY - JOUR TI - Transition layers at the SiO2/SiC interface AU - Zheleva, T. AU - Lelis, A. AU - Duscher, G. AU - Liu, F. AU - Levin, I. AU - Das, M. T2 - Applied Physics Letters DA - 2008/// PY - 2008/// VL - 93 IS - 2 ER - TY - JOUR TI - Thermal conductivity of semi-insulating, p-type, and n-type GaN films on sapphire AU - Jagannadham, K. AU - Berkman, E. A. AU - Elmasry, N. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - The thermal conductivity of undoped, n-type, and p-type GaN films deposited on (0001) substrates of sapphire was measured by the 3-ω method in the temperature range between 215 and 300K. The thickness, thermal conductivity, and heat capacity of the individual layers were used to simulate the experimental value of the increment in temperature of the heater using a multilayer model. The thermal conductivity of undoped GaN film was found to be much higher than that of p-type film. Also, the thermal conductivity of n-type GaN film was slightly smaller than that of p-type film. Modeling of the temperature dependence of the thermal conductivity in the films showed that phonon-dopant and three-phonon umklapp scattering are important. Smaller thickness and hence smaller volume fraction of the film with lower dislocation density was also found to be responsible for lower thermal conductivity in n- and p-type GaN films. DA - 2008/5// PY - 2008/5// DO - 10.1116/1.2899379 VL - 26 IS - 3 SP - 375-379 SN - 1520-8559 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-42949135532&partnerID=MN8TOARS ER - TY - JOUR TI - Synthesis and properties of barium titanate stannate thin films by chemical solution deposition AU - Ihlefeld, Jon F. AU - Borland, William J. AU - Maria, Jon-Paul T2 - JOURNAL OF MATERIALS SCIENCE DA - 2008/6// PY - 2008/6// DO - 10.1007/s10853-008-2618-x VL - 43 IS - 12 SP - 4264-4270 SN - 1573-4803 ER - TY - JOUR TI - Seeded growth of AlN on SiC substrates and defect characterization AU - Lu, P. AU - Edgar, J. H. AU - Cao, C. AU - Hohn, K. AU - Dalmau, R. AU - Schlesser, R. AU - Sitar, Z. T2 - JOURNAL OF CRYSTAL GROWTH AB - In this study, seeded sublimation growth of aluminum nitride (AlN) on SiC substrates was investigated. Large diameter (15–20 mm) and thick (1–2 mm) AlN layers were demonstrated on Si-face, 3.5° off-axis 6H-SiC (0 0 0 1). A c-axis growth rate of 15–20 μm/h was achieved at 1830 °C, and the surface morphology was highly textured: step features were formed with a single facet on the top of the layer. High-resolution X-ray diffraction (HRXRD), X-ray photoelectron spectroscopy (XPS), and molten KOH/NaOH etching were employed to characterize the AlN layers. The AlN crystals grew highly orientated along the c-axis, however, the impurities of Si (3–6 at%) and C (5.9–8 at%) from the SiC changed the lattice constants of AlN and shifted the AlN (0 0 .2) 2θ value from pure AlN toward SiC. All the growth surfaces had Al-polarity and the dislocation density decreased from 108 to 106 cm−2 as the film thickness increased from 30 μm to 2 mm. DA - 2008/5/1/ PY - 2008/5/1/ DO - 10.1016/j.jcrysgro.2008.01.010 VL - 310 IS - 10 SP - 2464-2470 SN - 1873-5002 KW - X-ray diffraction KW - growth from vapor KW - single-crystal growth KW - nitrides ER - TY - JOUR TI - Retardation of grain growth and cavitation by an electric field during superplastic deformation of ultrafine-grained 3Y-TZP at 1,450-1,600 degrees C AU - Yang, Di AU - Conrad, Hans T2 - JOURNAL OF MATERIALS SCIENCE DA - 2008/7// PY - 2008/7// DO - 10.1007/s10853-008-2653-7 VL - 43 IS - 13 SP - 4475-4482 SN - 0022-2461 ER - TY - JOUR TI - Plasma instabilities in magnetically assisted pulsed laser deposition AU - Haverkamp, J D AU - Bourham, M A AU - Du, S AU - Narayan, J T2 - Journal of Physics D: Applied Physics AB - The laser ablation of a carbon target in a transverse magnetic field is studied using a quadruple Langmuir probe. Ion saturation signals indicate the presence of wavelike behaviour not found in field-free laser ablation of carbon. Results are discussed in terms of the lower-hybrid drift instability and the electron–ion hybrid instability. The results are found to be most consistent with the electron–ion hybrid instability. DA - 2008/5/13/ PY - 2008/5/13/ DO - 10.1088/0022-3727/41/11/115206 VL - 41 IS - 11 SP - 115206 J2 - J. Phys. D: Appl. Phys. OP - SN - 0022-3727 1361-6463 UR - http://dx.doi.org/10.1088/0022-3727/41/11/115206 DB - Crossref ER - TY - JOUR TI - Observation of room temperature ferromagnetism in Ga:ZnO: A transition metal free transparent ferromagnetic conductor AU - Bhosle, V. AU - Narayan, J. T2 - Applied Physics Letters AB - This paper reports our results on room temperature ferromagnetism characteristics in Ga-doped ZnO. The Ga-doped ZnO films were grown epitaxially on (0001) sapphire with Ga concentration up to 5at.%. Detailed x-ray diffraction and high resolution transmission electron microscopy results showed a high-quality epitaxy without the presence of any secondary phases. Magnetic measurements showed characteristic ferromagnetism behavior with room temperature coercivity ∼50Oe, which remained fairly constant with temperature. Upon annealing coercivity disappeared with typical diamagnetic characteristics of ZnO. The x-ray photoelectron spectroscopy and electrical measurements as function of annealing showed a critical role of vacancies and Ga-vacancy complexes to be critical for the observed ferromagnetic behavior. DA - 2008/7/14/ PY - 2008/7/14/ DO - 10.1063/1.2953705 VL - 93 IS - 2 SP - 021912 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2953705 DB - Crossref ER - TY - JOUR TI - Newtonian viscous creep in Ti-3Al-2.5V AU - Gollapudi, Srikant AU - Bhosle, Vikram AU - Charit, Indrajit AU - Murty, K. Linga T2 - PHILOSOPHICAL MAGAZINE AB - Biaxial creep tests were performed on fine-grained Ti–3Al–2.5V tubing at 823 and 873 K in the stress range σ/E = 1.7 × 10−4 to σ/E = 5.9 × 10−4. Subsequently, the creep data were analysed to determine the stress exponent and activation energy. A stress exponent value of 1 and an activation energy equal to that for grain boundary diffusion were suggestive of a Coble creep-controlled deformation regime. However, discrepancy between the experimental creep rates and Coble creep model predictions along with subsequent observation of deformed microstructures decorated with slip bands implied the operation of a different viscous creep mechanism. A slip band model proposed by Spingarn and Nix was found to provide a better description of the experimental strain rates rather than the conventional viscous creep mechanisms. High-resolution transmission electron microscopy studies confirmed the nature of these bands. DA - 2008/// PY - 2008/// DO - 10.1080/14786430802144154 VL - 88 IS - 9 SP - 1357-1367 SN - 1478-6435 KW - titanium alloys KW - creep KW - diffusion KW - transmission electron KW - microscopy KW - HRTEM KW - Coble KW - slip band KW - Spingarn-Nix model ER - TY - JOUR TI - Modulated precursor flow epitaxial growth of AlN layers on native AlN substrates by metal-organic chemical vapor deposition AU - Kim, Hee Jin AU - Choi, Suk AU - Yoo, Dongwon AU - Ryou, Jae-Hyun AU - Dupuis, Russell D. AU - Dalmau, R. F. AU - Lu, P. AU - Sitar, Z. T2 - APPLIED PHYSICS LETTERS AB - We have investigated the growth of AlN layers on bulk AlN substrates by modulated precursor flow epitaxial growth using metal-organic and hydride precursors as well as by conventional metal-organic chemical vapor deposition growth. A nanopit-containing morphology was observed for an AlN layer grown by conventional growth, while atomically smooth and pit-free surface was achieved for an AlN layer created by modulated precursor flow epitaxial growth. For similar growth set-point temperatures, nanopit-free surfaces were observed for AlN layers created by conventional growth on sapphire substrates. This is believed to be due to the difference in the temperature of the growing surface, as evidenced by finite element method thermal profiling and the morphology change of the AlN layer with decreasing temperature observed for growth of AlN on sapphire substrates. The AlN layers grown by modulated precursor flow epitaxial growth on the AlN bulk substrates also have excellent crystalline qualities with narrow x-ray rocking curve peak linewidths of 36 and 61arcsec for the (002) and (102) diffraction conditions, respectively. DA - 2008/7/14/ PY - 2008/7/14/ DO - 10.1063/1.2959064 VL - 93 IS - 2 SP - SN - 1077-3118 ER - TY - JOUR TI - Model dielectric functions for AlxGa1-xAs alloys of arbitrary compositions AU - Jung, Y. W. AU - Kim, T. J. AU - Yoon, J. J. AU - Kim, Y. D. AU - Aspnes, D. E. T2 - JOURNAL OF APPLIED PHYSICS AB - Many optical models have been used to construct analytic composition-dependent dielectric functions of AlxGa1−xAs alloys. However, these models incorporate various unphysical assumptions to improve their fits to data. Here, we provide the parameters needed to calculate dielectric functions of AlxGa1−xAs for 1.5≤E≤6.0 eV and 0≤x≤1 by means of the parametric model of Johs et al. [Thin Solid Films 313–314, 137 (1998)], which eliminates these problems. A representative example concerning interface analysis is discussed, where it is necessary to construct a dielectric function of an alloy of essentially arbitrary composition. DA - 2008/7/1/ PY - 2008/7/1/ DO - 10.1063/1.2952536 VL - 104 IS - 1 SP - SN - 1089-7550 ER - TY - JOUR TI - Isolation of human mesenchymal stem cells from bone and adipose tissue AU - Bernacki, S. H. AU - Wall, M. E. AU - Loboa, E. G. T2 - Stem cell culture DA - 2008/// PY - 2008/// VL - 86 SP - 257-278 ER - TY - JOUR TI - Influence of gallium supersaturation on the properties of GaN grown by metalorganic chemical vapor deposition AU - Mita, S. AU - Collazo, R. AU - Rice, A. AU - Dalmau, R. F. AU - Sitar, Z. T2 - JOURNAL OF APPLIED PHYSICS AB - A thermodynamic supersaturation model for gallium (Ga) was developed to describe GaN growth characteristics in low-pressure metalorganic chemical vapor deposition. The model takes into account the simplified GaN chemical reaction that occurs at the growth interface, Ga+NH3=GaN+3/2H2. The supersaturation was varied in two ways: (1) by the V/III ratio and (2) by the choice of the diluent gas. Two diluent gases were considered: H2, a commonly used diluent gas, and N2, a reaction inert gas. The choice of the diluent played a role in the degree of Ga supersaturation; since H2 is the product in the GaN formation, the addition of hydrogen significantly lowered the supersaturation. Atomic force microscopy revealed that surface morphology was associated with the different Ga supersaturation and the Burton–Cabrera–Frank model was used to relate it to the observed spiral size and terrace width. In addition to growth morphology, the degree of Ga supersaturation also influenced the carrier compensation level in n-type GaN. Secondary ion mass spectrometry studies identified that the trend of carbon incorporation followed that of the compensation level and inversely that of the Ga supersaturation. For samples intentionally doped with Si, it was found that GaN became semi-insulating when the carbon concentration exceeded that of silicon. In general, it has been shown that two growth processes at seemingly different conditions will be equivalent if the corresponding Ga supersaturation is the same. This finding showed that the supersaturation is a much more universal parameter than any other growth parameter alone. DA - 2008/7/1/ PY - 2008/7/1/ DO - 10.1063/1.2952027 VL - 104 IS - 1 SP - SN - 0021-8979 ER - TY - JOUR TI - Impact of thermal annealing on deep-level defects in strained-Si/SiGe heterostructure AU - Zhang, R. H. AU - Rozgonyi, G. A. AU - Yakimov, E. AU - Yarykin, N. AU - Seacrist, M. T2 - Journal of Applied Physics DA - 2008/// PY - 2008/// VL - 103 IS - 10 ER - TY - JOUR TI - Impact of elemental arsenic on electrical characteristics of metal-oxide-semiconductor capacitors on GaAs using atomic-layer deposited HfO2 gate dielectric AU - Suri, Rahul AU - Lichtenwalner, Daniel J. AU - Misra, Veena T2 - APPLIED PHYSICS LETTERS AB - The interface between HfO2 and sulfur-passivated GaAs was analyzed after atomic-layer deposition (ALD) and postdeposition annealing (PDA) using x-ray photoelectron spectroscopy. The HfO2 ALD process resulted in elemental arsenic buildup at the interface. Electrical measurements confirmed that the elemental arsenic caused anomalously large values for equivalent oxide thickness (EOT), hysteresis, and frequency dispersion in accumulation. Arsenic outdiffusion after PDA lowered the EOT but increased the gate leakage. Annealing the (NH4)2S-treated GaAs prior to ALD yielded an EOT of 1.85nm and leakage of 6.6×10−4A∕cm2 at Vg=Vfb−1V. This modified passivation scheme looks promising for achieving a high-quality HfO2∕GaAs interface. DA - 2008/6/16/ PY - 2008/6/16/ DO - 10.1063/1.2949079 VL - 92 IS - 24 SP - SN - 1077-3118 ER - TY - JOUR TI - Direct Observation of Inversion Domain Boundaries of GaN onc-Sapphire at Sub-ångstrom Resolution AU - Liu, Fude AU - Collazo, Ramon AU - Mita, Seiji AU - Sitar, Zlatko AU - Pennycook, Stephen J. AU - Duscher, Gerd T2 - Advanced Materials AB - Inversion domain boundaries (IDBs) of GaN are studied by a high-resolution technique. The IDB separates adjacent domains of opposite polarity. The image shows a GaN IDB in the [bar;2110] projection. The theoretical IDB structure fits the experimentally obtained structure well. The inset is an image acquired from a very thin region on the right side of the IDB. It can indicate the polarity of GaN directly. DA - 2008/6/4/ PY - 2008/6/4/ DO - 10.1002/adma.200702522 VL - 20 IS - 11 SP - 2162-2165 J2 - Adv. Mater. LA - en OP - SN - 0935-9648 1521-4095 UR - http://dx.doi.org/10.1002/adma.200702522 DB - Crossref ER - TY - JOUR TI - Dependence of plasmon polaritons on the thickness of indium tin oxide thin films AU - Rhodes, C. AU - Cerruti, M. AU - Efremenko, A. AU - Losego, M. AU - Aspnes, D. E. AU - Maria, J.-P. AU - Franzen, S. T2 - Journal of Applied Physics AB - The evolution of polariton features with increasing thickness in p-polarized (TM) reflectance spectra of indium tin oxide (ITO) thin films deposited on BK7 glass reveals the nature of plasmons in conducting thin films without interference from band-to-band transitions or the tendency of very thin films to form islands, both of which are complicating factors with the noble metals Au and Ag. Although the dependence on energy, film thickness, and angle of incidence is complex, these features are accurately described by the three-phase (substrate/overlayer/ambient) Fresnel model using only the Drude free-electron representation for the dielectric function of the ITO film. For film thicknesses less than 80nm the relevant excitation is a one-dimensional screened-bulk plasmon (SBP) that corresponds to charge transfer across the entire film. The associated SBP polariton (SBPP) occurs at the energy of the SBP and is relatively independent of the angle of incidence. For film thicknesses greater than 120nm, the relevant excitation is the surface plasmons (SP). The associated surface plasmon polariton (SPP) exhibits the usual strong dependence of energy on the angle of incidence. For larger thicknesses this structure gradually weakens, in agreement with theory. No other collective excitations are observed. The optimum thicknesses for the SPP in ITO is 160nm, whereas the SBPP is observed only when the film thickness is less than 70nm. The SBPP exhibits many of the features that make the SPP attractive for both science and technology, but has not been observed previously. Our results show that ITO films, in particular, and conducting-metal-oxide films in general provide new opportunities for investigating plasmons in conductors and obtaining new insights into plasmons, plasmon polaritons, and related optical phenomena. DA - 2008/5// PY - 2008/5// DO - 10.1063/1.2908862 VL - 103 IS - 9 SP - 093108 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.2908862 DB - Crossref ER - TY - JOUR TI - Conformal metal oxide coatings on nanotubes by direct low temperature metal-organic pyrolysis in supercritical carbon dioxide AU - Peng, Qing AU - Spagnola, Joseph C. AU - Daisuke, Hojo AU - Park, Kie Jin AU - Parsons, Gregory N. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - The authors demonstrate that low temperature (&lt;200 °C) thermal decomposition of metal-organic precursors dissolved in supercritical carbon dioxide (scCO2) is an effective method to penetrate into dense three-dimensional networks and deposit conformal metal oxide films with tunable thickness. The results specifically show that thermal decomposition of gallium acetylacetonate in scCO2, leads to conformal coatings of gallium oxide on multiwalled carbon nanotube forests with a fast deposition rate (∼3–4 nm/min), without the need for any cosolvent. Moreover, as-formed metal oxide/nanotube structures can be further conformally coated by metal atomic layer deposition to produce nanotube/oxide/metal nanocomposites. DA - 2008/5// PY - 2008/5// DO - 10.1116/1.2917072 VL - 26 IS - 3 SP - 978-982 SN - 2166-2746 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000256304600016&KeyUID=WOS:000256304600016 ER - TY - JOUR TI - Analysis of V defects in GaN-based light emitting diodes by scanning transmission electron microscopy and electron beam induced current AU - Progl, C. L. AU - Parish, C. M. AU - Vitarelli, J. P. AU - Russell, P. E. T2 - Applied Physics Letters DA - 2008/// PY - 2008/// VL - 92 IS - 24 ER - TY - JOUR TI - The nearly aligned rotating-monoplate compensator AU - Asar, M. AU - Aspnes, D. E. T2 - PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE AB - Abstract A rotating‐compensator polarimeter with a misaligned monoplate compensator generates first, third, and fifth harmonics as well as the zeroth (dc), second, and fourth harmonics that provide information about the sample. We outline a general procedure for calculating the detected intensity with mis‐ aligned components, then provide some results where multiple internal reflections in the component are ignored. The analysis involves several orders of tensors, and a quartic secular equation instead of the usual quadratic of a quadratic. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2008/4// PY - 2008/4// DO - 10.1002/pssa.200777871 VL - 205 IS - 4 SP - 739-742 SN - 1862-6300 ER - TY - JOUR TI - The anisotropic bond model of nonlinear optics AU - Adles, E. J. AU - Aspnes, D. E. T2 - physica status solidi (a) AB - Abstract The anisotropic‐bond model (ABM) of nonlinear optics (NLO) provides a simple means of calculating NLO properties of materials by factoring the problem into four parts: first, determination of the local field at a bond‐charge site; second, solution of the anharmonic force equation of the bond charge; third, calculation of the radiation from the charge; and fourth, superposition of the radiation from all charges. Because this factorization is impossible in linear optics, this is one of the few cases where a nonlinear problem is simpler than its linear equivalent. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2008/4// PY - 2008/4// DO - 10.1002/pssa.200777846 VL - 205 IS - 4 SP - 728-731 J2 - phys. stat. sol. (a) LA - en OP - SN - 1862-6300 1862-6319 UR - http://dx.doi.org/10.1002/pssa.200777846 DB - Crossref ER - TY - JOUR TI - Temperature dependence of single-asperity diamond-diamond friction elucidated using AFM and MD Simulations AU - Brukman, Matthew J. AU - Gao, Guangtu AU - Nemanich, Robert J. AU - Harrison, Judith A. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - Complementary experimental (atomic force microscopy) and theoretical (molecular dynamics) techniques were used to investigate friction between diamond−diamond junctions as a function of temperature. The simulation and experimental conditions were designed to correspond as closely as possible. In the atomic force microscopy (AFM) experiments, two microcrystalline-diamond (μCD) AFM tips of differing contact radii were used to examine the friction of diamond (111) and (001) single crystals from 24 to 225 K in an ultrahigh vacuum. At all temperatures, the experimentally determined dependence of friction on load was consistent with the occurrence of single-asperity interfacial friction, where friction is proportional to contact area. In addition, the behavior of the contact was fit well by the Derjaguin−Muller−Toporov continuum model. Friction measurements within a given series were highly repeatable; however, as is typical with AFM measurements, there was some variation in measurements taken from different regions of the sample and with different tips. Interfacial shear strength, or the intrinsic resistance to sliding, decreased slightly with increasing temperature for both surfaces. To shed additional insight into the AFM results, MD simulations were performed with the diamond single crystals of the same orientation. The calculations also show that the average friction force decreased slightly as the temperature increased for both diamond surfaces and for all sliding directions. Both AFM and MD results agree with the numerical analysis of friction as a function of temperature published by Sang et al. (Sang, Y.; Dube, M.; Grant, M. Phys. Rev. Lett. 2001, 87, 174301). DA - 2008/6/26/ PY - 2008/6/26/ DO - 10.1021/jp711959e VL - 112 IS - 25 SP - 9358-9369 SN - 1932-7455 ER - TY - JOUR TI - Run-in behavior of nanocrystalline diamond coatings studied by in situ tribometry AU - Chromik, Richard. R. AU - Winfrey, A. Leigh AU - Luening, Jan AU - Nemanich, Robert J. AU - Wahl, Kathryn J. T2 - WEAR AB - The friction performance of nanocrystalline diamond coatings was evaluated using in situ tribometry with sapphire counterfaces. Coatings were grown by microwave plasma assisted chemical vapor deposition in an Ar–H–CH4 plasma, with H ranging from 0 to 36%. In situ examination of the sliding contact, combined with ex situ analysis of the sapphire counterface revealed that the velocity accommodation mode was interfacial sliding of a carbonaceous transfer film versus the coating wear track. For most tests, the contact diameter increased during the first 50 sliding cycles and then remained constant. The in situ measure of the contact diameter was found to correlate confidently to ex situ measurements of counterface wear. The performance of the diamond coatings, characterized by quick run-in to low friction was best when a small but detectable graphite peak was present in the X-ray diffraction (XRD) profile. The relative intensity of the XRD graphite peak was also found to directly correlate with the peak position of the C1s → π* transition as measured by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Increasing the relative amount of graphite-bonded sp2 carbon in the NCD films decreased run-in cycles to low friction. DA - 2008/7/31/ PY - 2008/7/31/ DO - 10.1016/j.wear.2007.11.023 VL - 265 IS - 3-4 SP - 477-489 SN - 1873-2577 KW - diamond KW - friction KW - nanocrystalline diamond KW - in situ tribometry KW - wear KW - NEXAFS ER - TY - JOUR TI - Inverse grain-size effect on twinning in nanocrystalline Ni AU - Wu, X. L. AU - Zhu, Y. T. T2 - PHYSICAL REVIEW LETTERS AB - A long-standing controversy exists between molecular dynamics simulations and experiments on the twinning propensity of nanocrystalline (NC) face-centered-cubic metals. For example, three-dimensional molecular dynamics simulations rarely observed twins in NC Ni, whereas experiments readily observed them. Here this discrepancy is resolved by experimental observation of an inverse grain-size effect on twinning. Specifically, decreasing the grain size first promotes twinning in NC Ni and then hinders twinning due to the inverse grain-size effect. Interestingly, no inverse grain-size effect exists on stacking fault formation. These observations are explained by generalized planar fault energies and grain-size effect on partial emissions. DA - 2008/7/11/ PY - 2008/7/11/ DO - 10.1103/physrevlett.101.025503 VL - 101 IS - 2 SP - SN - 1079-7114 ER - TY - JOUR TI - Further investigation of crystal hardening inequalities in (110) channel die compression AU - Havner, Kerry S. T2 - PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES AB - A set of geometrically based FCC crystal slip-systems hardening inequalities is analytically investigated in (110) channel die compression for all lateral constraint directions between and , following previous analyses of the other two distinct orientation ranges in (110) compression. With all critical slip systems active, it is proved that these inequalities uniquely predict initial lattice stability and finite crystal shearing only in the horizontal channel plane, consistent with experiments for this range of orientations. (The earlier analyses had predicted load-axis stability in both orientation ranges, and lattice stability in one, also commonly found experimentally.) Moreover, it is established that the lateral constraint stress predicted by the hardening inequalities will be less than that given by classic Taylor hardening as this stress evolves with deformation. It is further shown, taking into account experimental stress–strain curves and latent hardening experiments for aluminium and copper, that lattice stability generally can be expected to very large deformations, except perhaps for lateral constraint orientations near the end of the range, which result is consistent with experiment. In appendix A, the possibilities of solutions with a critical slip system inactive are investigated, and predictions of a power law rate-dependent plasticity model are analysed for comparison with the results based on the hardening inequalities. DA - 2008/8/8/ PY - 2008/8/8/ DO - 10.1098/rspa.2007.0272 VL - 464 IS - 2096 SP - 1955-1982 SN - 1364-5021 KW - channel die compression KW - FCC crystals KW - slip-systems hardening inequalities KW - finite deformation analysis ER - TY - JOUR TI - Direct metal fabrication of titanium implants with tailored materials and mechanical properties using electron beam melting technology AU - Harrysson, Ola L. A. AU - CansiZoglu, Omer AU - Marcellin-Little, Denis J. AU - Cormier, Denis R. AU - West, Harvey A., II T2 - MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS AB - The design of custom or tailored implant components has been the subject of research and development for decades. However, the economic feasibility of fabricating such components has proven to be a challenge. New direct metal fabrication technologies such as Electron Beam Melting (EBM) have opened up new possibilities. This paper discusses the design and fabrication of titanium implant components having tailored mechanical properties that mimic the stiffness of bone to reduce stress shielding and bone remodeling. Finite Element Analysis was used to design the tailored structures, and results were verified using mechanical testing. DA - 2008/4/1/ PY - 2008/4/1/ DO - 10.1016/j.msec.2007.04.022 VL - 28 IS - 3 SP - 366-373 SN - 0928-4931 KW - orthopedic implants KW - electron beam melting KW - theoretical modeling KW - materials KW - experimentation ER - TY - JOUR TI - Dielectric properties of InAsP alloy thin films and evaluation of direct- and reciprocal-space methods of determining critical-point parameters AU - Choi, S. G. AU - Aspnes, D. E. AU - Stoute, N. A. AU - Kim, Y. D. AU - Kim, H. J. AU - Chang, Y. -C. AU - Palmstrom, C. J. T2 - PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE AB - Abstract Spectroscopic ellipsometry is used to determine pseudodielectric function spectra 〈 ε 〉 = 〈 ε 1 〈 + i 〈 ε 2 〈 of InAs x P 1– x al‐loy thin films from 1.5 to 6.0 eV at room temperature. The structures for the E 1 , E 1 + Δ 1 , E ′ 0 , E 2 , and E ′ 2 critical points (CPs) were observed in the data. We compare direct‐ and reciprocal‐space methods of extracting CP energies E g . The direct‐space values show less uncertainty, a result of how the two procedures use available information. Energies obtained are compared with the results of theoretical calculations using the linear augmented Slater‐type orbital (LASTO) method. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2008/4// PY - 2008/4// DO - 10.1002/pssa.200777848 VL - 205 IS - 4 SP - 884-887 SN - 1862-6300 ER - TY - JOUR TI - Creep mechanisms in TI-3Al-2.5V alloy tubing deformed under closed-end internal gas pressurization AU - Gollapudi, S. AU - Charit, I. AU - Murty, K. L. T2 - ACTA MATERIALIA AB - Creep tests were carried out on Ti–3Al–2.5V alloy tubing in the temperature range of 723–873 K under closed-end internal pressurization. The data thus obtained were analyzed to obtain the mechanistic creep parameters (stress exponent and activation energy). Transitions in creep mechanisms were noted as the stress exponent varied from a lower value of 1 through 2 to a higher value of 5 with increasing stress where the activation energy assumed values of 232 and 325 kJ mol−1, respectively. The creep mechanisms were elucidated in the light of standard creep models supported by the substructures studied by transmission electron microscopy. Newtonian viscous creep (n = 1) at lower stresses was identified to be in accordance with a slip band model named after Spingarn and Nix. Grain boundary sliding with n = 2 was noted in an intermediate stress region while climb of edge dislocations was observed to control creep at higher stresses. Microstructural observations along with parametric variations of creep rates were useful in identifying the underlying deformation mechanisms. DA - 2008/6// PY - 2008/6// DO - 10.1016/j.actamat.2008.01.052 VL - 56 IS - 10 SP - 2406-2419 SN - 1873-2453 KW - titanium alloys KW - creep KW - diffusion KW - transmission electron microscopy KW - slip band ER - TY - JOUR TI - Characterization of palladium (Pd) on alumina catalysts prepared using liquid carbon dioxide AU - Kim, Jaehoon AU - Kelly, M. Jason AU - Lamb, H. Henry AU - Roberts, George W. AU - Kiserow, Douglas J. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - Palladium (II) hexafluoroacetylacetonate (Pd(hfac)2) dissolved in liquid carbon dioxide (L-CO2) was used to deposit Pd nanoparticles onto low-surface-area α-alumina (13 m2/g) and high-surface-area γ-alumina (207 m2/g). These nanoparticles were prepared by contacting Pd(hfac)2 dissolved in L-CO2 with the alumina at 6.9 MPa and 28.5 °C and then slowly venting gaseous CO2 until L-CO2 was completely evaporated. After depressurization to remove the CO2 and unabsorbed Pd(hfac)2, the impregnated Pd(hfac)2 was reduced in hydrogen at a relatively low temperature of 75 °C. The adsorption isotherm of Pd(hfac)2 on γ-alumina suggests a weak interaction between the organometallic compound and the support. The average Pd particle size on the low-surface-area α-alumina, measured by scanning electron microscopy, increased from 13.1 ± 3.5 to 59.9 ± 11.3 nm, and the metal dispersion, measured by pulsed CO chemisorption, decreased from 11 to 3%, as the Pd loading on the alumina was increased from 0.15 to 1.54 wt %. With the high-surface-area γ-alumina, Pd particle size, measured by scanning transmission electron microscopy, increased from 3.1 ± 1.9 to 7.0 ± 5.9 nm, and the metal dispersion decreased from 56 to 5%, as Pd loading was increased from 0.58 to 3.94 wt %. DA - 2008/7/17/ PY - 2008/7/17/ DO - 10.1021/jp711495n VL - 112 IS - 28 SP - 10446-10452 SN - 1932-7447 ER - TY - JOUR TI - Capacitance transient and current-/capacitance-voltage study of direct silicon bonded (110)/(100) interface AU - Yu, X. G. AU - Lu, J. G. AU - Rozgonyi, G. T2 - Applied Physics Letters DA - 2008/// PY - 2008/// VL - 92 IS - 26 ER - TY - JOUR TI - Advanced processing of biomaterials AU - Narayan, Roger Jagdish AU - Bochlert, Carl T2 - MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS DA - 2008/4/1/ PY - 2008/4/1/ DO - 10.1016/j.msec.2007.04.001 VL - 28 IS - 3 SP - 321-322 SN - 0928-4931 ER - TY - JOUR TI - A mimetic porous carbon model by quench molecular dynamics simulation AU - Shi, Y. F. T2 - Journal of Chemical Physics DA - 2008/// PY - 2008/// VL - 128 IS - 23 ER - TY - JOUR TI - stee Distribution and segregation of arsenic at the SiO2/Si interface AU - Steen, C. AU - Martinez-Limia, A. AU - Pichler, P. AU - Ryssel, H. AU - Paul, S. AU - Lerch, W. AU - Pei, L. AU - Duscher, G. AU - Severac, F. AU - Cristiano, F. AU - Windl, W. T2 - Journal of Applied Physics DA - 2008/// PY - 2008/// VL - 104 IS - 2 ER - TY - JOUR TI - The role of creep in the time-dependent resistance of Ohmic gold contacts in radio frequency microelectromechanical system devices AU - Rezvanian, O. AU - Brown, C. AU - Zikry, M. A. AU - Kingon, A. I. AU - Krim, J. AU - Irving, D. L. AU - Brenner, D. W. T2 - Journal of Applied Physics AB - It is shown that measured and calculated time-dependent electrical resistances of closed gold Ohmic switches in radio frequency microelectromechanical system (rf-MEMS) devices are well described by a power law that can be derived from a single asperity creep model. The analysis reveals that the exponent and prefactor in the power law arise, respectively, from the coefficient relating creep rate to applied stress and the initial surface roughness. The analysis also shows that resistance plateaus are not, in fact, limiting resistances but rather result from the small coefficient in the power law. The model predicts that it will take a longer time for the contact resistance to attain a power law relation with each successive closing of the switch due to asperity blunting. Analysis of the first few seconds of the measured resistance for three successive openings and closings of one of the MEMS devices supports this prediction. This work thus provides guidance toward the rational design of Ohmic contacts with enhanced reliabilities by better defining variables that can be controlled through material selection, interface processing, and switch operation. DA - 2008/7/15/ PY - 2008/7/15/ DO - 10.1063/1.2953072 VL - 104 IS - 2 SP - 024513 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.2953072 DB - Crossref ER - TY - JOUR TI - Self-catalyzed hydrogenolysis of nickelocene: Functional metal coating of three-dimensional nanosystems at low temperature AU - Peng, Qing AU - Spagnola, Joseph C. AU - Parsons, Gregory N. T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - In this paper we demonstrate the hydrogenolysis of nickelocene can take place through a self-catalyzed process at low temperature in supercritical carbon dioxide to generate relatively uniform dispersed Ni (nickel) metal particles onto carbon nanotubes forests and Ni films on flat surfaces. The ability to form metal particles or films without a local catalyst at this low temperature is significant because it provides further insight into mechanisms for Ni deposition reactions, and it enables a new route for low-temperature metal coating on a range of nonmetal substrate materials with complex topographies and nanostructures, for example, to form Ni/polymer magnetic nanocomposites. DA - 2008/// PY - 2008/// DO - 10.1149/1.2946723 VL - 155 IS - 9 SP - D580-D582 SN - 0013-4651 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000258038800037&KeyUID=WOS:000258038800037 ER - TY - PAT TI - Pendeoepitaxial gallium nitride semiconductor layers on silicon carbide substrates AU - Linthicum, K. J. AU - Gehrke, T. AU - Thomson, D. B. AU - Carlson, E. P. AU - Rajagopal, P. AU - Davis, R. F. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Interfacial and solvent effects govern the formation of tris(dibenzylidenacetone)dipalladium(0) microstructures AU - Leonard, Donovan N. AU - Cerruti, Marta AU - Duscher, Gerd AU - Franzen, Stefan T2 - LANGMUIR AB - Organometallic palladium adducts have application as catalysts and as precursors for nanoparticle synthesis. Herein, we study the spontaneous formation of molecular crystals of the organometallic reagent tris(dibenzylidenacetone)dipalladium(0) (Pd2(DBA)3) in THF/H2O binary solvent systems. We report structural and chemical characterization of the resulting diverse structures with shapes including hexagonal platelets, rods, cubes, and stars. Optical microscopy, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectroscopy were used to determine representative structures and corresponding compositions when formed either in a binary solution or upon evaporation on a surface. The difference in Pd2(DBA)3 particle morphology was attributed to differences in the surface tension of growing crystalline faces. The formation of a majority of rods or hexagonal platelets in solution was shown to be determined by the ratio of THF to H2O in the solvent, whereas supersaturation effects and interfacial surface tension played a major role in creating the shape of particles formed upon evaporation of Pd2(DBA)3 droplets on a surface. DA - 2008/8/5/ PY - 2008/8/5/ DO - 10.1021/la801039j VL - 24 IS - 15 SP - 7803-7809 SN - 0743-7463 ER - TY - JOUR TI - Influence of specimen dimensions on the tensile behavior of ultrafine-grained Cu AU - Zhao, Y. H. AU - Guo, Y. Z. AU - Wei, Q. AU - Dangelewiez, A. M. AU - Zhu, Y. T. AU - Langdon, T. G. AU - Zhou, Y. Z. AU - Lavernia, E. J. AU - Xu, C. T2 - SCRIPTA MATERIALIA AB - Miniature dog-bone specimens with different sizes and geometries are frequently used to measure the tensile behaviors of nanostructured materials. Here we report a significant specimen dimensions influence on the tensile behavior of ultrafine-grained Cu: the elongation to failure, post-necking elongation and strain hardening rate all increase with increasing thickness or decreasing gauge length. The thickness effect is caused by the necking geometry and the effect of gauge length originates from the strain definition. DA - 2008/9// PY - 2008/9// DO - 10.1016/j.scriptamat.2008.05.031 VL - 59 IS - 6 SP - 627-630 SN - 1359-6462 KW - ultrafine-grained Cu KW - specimen size and geometry KW - tensile ductility KW - finite element modeling (FEM) ER - TY - JOUR TI - Grain-size stabilization in nanocrystalline FeZr alloys AU - Darling, Kris A. AU - Chan, Ryan N. AU - Wong, Patrick Z. AU - Semones, Jonathan E. AU - Scattergood, Ronald O. AU - Koch, Carl C. T2 - SCRIPTA MATERIALIA AB - Nanocrystalline Fe–Zr alloys with a nominal grain size of 10 nm were synthesized by mechanical alloying. The grain size in pure Fe was >200 nm after annealing for 1 h at T/TM = 0.5. Additions of 1 at.% Zr stabilized the grain size at 50 nm up to T/TM = 0.92. Particle pinning, solute drag and reduction in grain-boundary energy have been proposed as stabilization mechanisms. The stabilization in Fe–Zr alloys is attributed to a reduction in grain-boundary energy due to Zr segregation. DA - 2008/9// PY - 2008/9// DO - 10.1016/j.scriptamat.2008.04.045 VL - 59 IS - 5 SP - 530-533 SN - 1359-6462 KW - nanostructure KW - iron alloys KW - mechanical milling KW - grain growth KW - segregation ER - TY - JOUR TI - Effects of adhesion layers on the ferroelectric properties of lead zirconium titanate thin films deposited on silicon nitride coated silicon substrates AU - Zohni, Omar AU - Buckner, Gregory AU - Kim, Taeyun AU - Kingon, Angus AU - Maranchi, Jeff AU - Siergiej, Richard T2 - THIN SOLID FILMS AB - We have investigated the addition of silicon nitride (Si3N4) thin films into sol–gel deposited lead zirconium titanate (PZT) stacks and quantified the effects of various adhesion layers on the ferroelectric characteristics of these stacks. Although previous research has investigated issues related to the adhesion characteristics of PZT films, this research considers four specific adhesion layers deposited onto a silicon nitride coated substrate: zirconium (Zr), zirconium dioxide (ZrO2), titanium (Ti) and tantalum (Ta), and compares experimental characteristics of each. Adhesion layer thicknesses of 15 nm and 25 nm were tested with pyrolysis temperatures of 600 °C and 650 °C. For many of the adhesion layers, the remnant polarization Pr and capacitance–voltage (C–V) characteristics are similar to conventional PZT stacks deposited onto silicon dioxide (SiO2) coated substrates, but only Ta withstands the thermal processing required for PZT deposition. DA - 2008/7/31/ PY - 2008/7/31/ DO - 10.1016/j.tsf.2007.10.130 VL - 516 IS - 18 SP - 6052-6057 SN - 0040-6090 KW - silicon nitride KW - PZT KW - tantalum KW - adhesion KW - electrical properties and measurements ER - TY - JOUR TI - Deformation twin formed by self-thickening, cross-slip mechanism in nanocrystalline Ni AU - Wu, X. L. AU - Narayan, J. AU - Zhu, Y. T. T2 - Applied Physics Letters AB - We report the observation of a deformation twin formed by a recently proposed self-thickening, cross-slip twinning mechanism. This observation verifies one more twinning mechanism, in addition to those reported before, in nanocrystalline face-centered-cubic metals. In this mechanism, once the first Shockley partial is emitted from a grain boundary, and cross slips onto another slip plane, a deformation twin could nucleate and grow in both the primary and cross-slip planes without requiring the nucleation of additional Shockley partials from the grain boundary. DA - 2008/7/21/ PY - 2008/7/21/ DO - 10.1063/1.2949685 VL - 93 IS - 3 SP - 031910 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2949685 DB - Crossref ER - TY - PAT TI - Vertical junction field effect transistor having an epitaxial gate AU - Harris, C. AU - Konstantinov, A. AU - Basceri, C. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Titanium Interlayer Mediated Epitaxy of CoSi2 on Si1-xGex AU - Burnette, James E. AU - Kiesel, Sharon AU - Sayers, Dale E. AU - Nemanich, Robert J. T2 - THIN SOLID FILMS AB - Abstract Titanium Interlayer Mediated Epitaxy (TIME) has been shown to promote the formation of epitaxial CoSi2 on Si (100). Similarities between Si and Si1−xGex alloys have motivated a study of whether the TIME process could be successful in forming epitaxial CoSi2 on Si1−xGex. Titanium layers of varying thickness were deposited as interlayers between a Co layer and c-Si/Si0.8Ge0.2 grown epitaxially onto Si (100) to investigate their role in the formation of epitaxial CoSi2 on Si1−xGex alloys. The effect of Ti interlayer thickness on the orientation of CoSi2 to the Si1−xGex substrate, and the conditions under which a polycrystalline CoSi2 film has been formed have been studied. It was found that Ti was beneficial in promoting epitaxy to the substrate in all cases. The experimental results indicate that with a Ti interlayer thickness of ∼ 50 A, the formation of epitaxial CoSi2 adjacent to the substrate was achieved, and pinhole formation was minimized. It was also observed that for increased interlayer thickness, Ti reacted with Si to form a titanium silicide. DA - 2008/2/29/ PY - 2008/2/29/ DO - 10.1016/j.tsf.2007.08.045 VL - 516 IS - 8 SP - 1809-1817 SN - 0040-6090 KW - CoSi2 KW - Si1-xGex KW - epitaxy KW - Ti interlayer KW - TIME process KW - XANES KW - XRD KW - pinhole formation ER - TY - JOUR TI - Thermodynamics and kinetic processes of polymer blends and block copolymers in the presence of pressurized carbon dioxide AU - Walker, Teri A. AU - Frankowski, David J. AU - Spontak, Richard J. T2 - ADVANCED MATERIALS AB - Abstract Environmentally‐responsible materials processing is becoming an important global consideration in a wide variety of technologies, especially those wherein volatile and/or residual organic solvents cannot be tolerated. In this context, polymer processing has benefited tremendously from advances achieved using high‐pressure CO 2 as a viscosity modifier, plasticizing agent, foaming agent, and reaction medium. Pressurized CO 2 is environmentally benign, inexpensive, sustainable, and versatile owing to its gas‐like viscosity and liquid‐like solubility, which can be tuned through judicious choice of temperature and pressure. The addition of high‐pressure CO 2 to homopolymer blends and block copolymers can have a profound impact on polymer thermodynamics and kinetic processes since the number of interacting species increases. As a result, the compressibility as well as plasticization and intermolecular screening effects become non‐negligible. In this work, we review how these factors influence such polymeric systems, and discuss commercial polymer processes and applications that benefit from the use of high‐pressure CO 2 . DA - 2008/3/5/ PY - 2008/3/5/ DO - 10.1002/adma.200700076 VL - 20 IS - 5 SP - 879-898 SN - 1521-4095 ER - TY - JOUR TI - Thermodynamic and kinetic study of transport and reaction phenomena in gallium nitride epitaxy growth AU - Cai, D. AU - Mecouch, W. J. AU - Zheng, L. L. AU - Zhang, H. AU - Sitar, Z. T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER AB - An iodine vapor phase epitaxy (IVPE) system has been designed and built to grow high quality thick gallium nitride film at the growth rate up to 80 μm/h with the deposition temperature of 1050 °C and the pressure of 200 torr. Numerical and experimental studies have been performed to investigate heat and mass transport and reaction phenomena in a vertical reactor. Geometrical parameters and operating conditions are optimized to achieve high and uniform GaN deposition rate. Gas phase and surface reactions in the growth chamber have been analyzed thermodynamically and kinetically, and primary transport species and important reactions are identified. The rate expressions for different surface reactions are determined and their contributions to the GaN deposition rate are studied for different V/III ratios. The sticking probability of the main reactants and adsorption activation energy are calculated. DA - 2008/3// PY - 2008/3// DO - 10.1016/j.ijheatmasstransfer.2007.12.004 VL - 51 IS - 5-6 SP - 1264-1280 SN - 0017-9310 KW - computer simulation KW - heat and mass transfer KW - chemical reaction KW - thermodynamics KW - kinetics KW - semiconductor KW - gallium nitride ER - TY - JOUR TI - The effect of water and guest hydrophobicity on the complexation of oligomers with solid alpha-cyclodextrin AU - Hunt, Marcus A. AU - Tonelli, Alan E. AU - Balik, C. Maurice T2 - POLYMER AB - α-Cyclodextrin (α-CD), a cyclic oligosaccharide, can form inclusion complexes (ICs) with polymer molecules in which α-CD molecules stack in the columnar crystal to form a molecular tube. Physical mixtures of α-CD powder and oligomeric liquids such as poly(ethylene glycol) (PEG) have been shown to spontaneously form an IC, which is accompanied by a solid-state α-CD phase transformation from the cage to the columnar crystal structure. In this paper, the phase transformation is tracked with wide-angle X-ray diffraction as a function of temperature, atmospheric water vapor content and the type of guest molecule. A first-order kinetic model is used to describe the kinetics of complexation. The time required to completely complex PEG200 (200 g/mol) at low water activities is greater than 300 h, whereas only a few hours are necessary at high water activities. Solid-state complexation of α-CD with a hydrophobic guest molecule (hexatriacontane, HTC), is also reported here for the first time. Slower complexation kinetics are observed for α-CD with HTC compared to PEG600 (600 g/mol). DA - 2008/2/18/ PY - 2008/2/18/ DO - 10.1016/j.polymer.2008.01.007 VL - 49 IS - 4 SP - 985-991 SN - 0032-3861 KW - alpha-cyclodextrin KW - inclusion complex KW - phase transformation ER - TY - JOUR TI - Suppression of Ge-O and Ge-N bonding at Ge-HfO2 and Ge-TiO2 interfaces by deposition onto plasma-nitrided passivated Ge substrates: Integration issues Ge gate stacks into advanced devices AU - Lee, S. AU - Long, J. P. AU - Lucovsky, G. AU - Whitten, J. L. AU - Seo, H. AU - Luning, J. T2 - MICROELECTRONICS RELIABILITY AB - A study of changes in nano-scale morphology of thin films of nano-crystalline transition metal (TM) elemental oxides, HfO2 and TiO2, on plasma-nitrided Ge(1 0 0) substrates, and Si(1 0 0) substrates with ultra-thin (∼0.8 nm) plasma-nitrided Si suboxide, SiOx, x < 2, or SiON interfacial layers is presented. Near edge X-ray absorption spectroscopy (NEXAS) has been used to determine nano-scale morphology of these films by Jahn-Teller distortion removal of band edge d-state degeneracies. These results identify a new and novel application for NEXAS based on the resonant character of the respective O K1 and N K1 edge absorptions. This paper also includes a brief discussion of the integration issues for the introduction of this Ge breakthrough into advanced semiconductor circuits and systems. This includes a comparison of nano-crystalline and non-crystalline dielectrics, as well as issues relative to metal gates. DA - 2008/3// PY - 2008/3// DO - 10.1016/j.microrel.2007.07.068 VL - 48 IS - 3 SP - 364-369 SN - 0026-2714 ER - TY - PAT TI - Supercritical fluid technology for cleaning processing chambers and systems AU - Basceri, C. AU - Sandhu, G. S. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Structure-magnetic property correlations in the epitaxial FePt system AU - Trichy, G. R. AU - Chakraborti, D. AU - Narayan, J. AU - Prater, J. T. T2 - Applied Physics Letters AB - We present findings on the effect of microstructure on magnetic properties of the epitaxial FePt system. Epitaxial c-axis oriented FePt was synthesized on Si (100) using TiN as a template buffer. The microstructure was progressively varied from a 9nm nanoparticle system to a 30nm thick continuous thin film. We found that individual nanoparticles showed higher coercivity than the continuous thin film. Within the nanoparticle regime, coercivity increased with increasing particle size. The highest coercivity of 13500Oe was realized for a beadlike microstructure, when the individual nanoparticles just begin to merge to form a continuous thin film. DA - 2008/3/10/ PY - 2008/3/10/ DO - 10.1063/1.2883933 VL - 92 IS - 10 SP - 102504 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2883933 DB - Crossref ER - TY - JOUR TI - Spectroscopic analysis of the epitaxial CaO (111)-GaN (0002) interface AU - Craft, H. S. AU - Collazo, R. AU - Losego, M. D. AU - Mita, S. AU - Sitar, Z. AU - Maria, J. -P. T2 - APPLIED PHYSICS LETTERS AB - We report an x-ray photoelectron spectroscopy (XPS) study of the CaO∕GaN interface. Epitaxial films of CaO (111) were grown on GaN (0002) and analyzed in situ using XPS. We observe Stranski–Krastanov growth, in which CaO coalesces rapidly, then converts to a three-dimensional mode. Data suggest coalescence within the first nanometer of film growth, indicating growth behavior different from published reports of the analogous MgO–GaN system. We find 1.0±0.2eV for the valence band offset and a 2.5±0.2eV conduction band offset. The results are discussed in terms of their utility in oxide-nitride electronic devices. DA - 2008/2/25/ PY - 2008/2/25/ DO - 10.1063/1.2887878 VL - 92 IS - 8 SP - SN - 0003-6951 ER - TY - PAT TI - Semiconductor manufacturing apparatus for modifying-in-film stress of thin films, and product formed thereby AU - Basceri, C. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Semiconductor device-based sensors AU - Johnson, J. W. AU - Piner, E. L. AU - Linthicum, K. J. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Self-assembled three-dimensional Cu-Ge nanoweb composite AU - Darling, Kris A. AU - Reynolds, C. Lewis, Jr. AU - Leonard, Donovan N. AU - Duscher, Gerd AU - Scattergood, Ronald O. AU - Koch, Carl C. T2 - NANOTECHNOLOGY AB - The inexpensive combination of cryogenically milled Cu3Ge powders sonochemically processed in a standard ultrasonic cleaner has led to the prototype of a heretofore undescribed class of material. This prototype is a nanostructured composite composed of 4.5 nm diameter Cu nanocrystals embedded in a three-dimensional (3D) amorphous CuGeO3 polyhedron web matrix. The diameters of the wires comprising the matrix are typically 5–15 nm. Complete structural and compositional characterization is reported to provide additional insight and firm designation on the observation of this previously undescribed class of material. The large surface to volume ratio of these nanoweb composites may offer unique advantages based on altered optical or electronic and magnetic properties. For example, quantum confinement of the Cu dots in the amorphous 3D nanowebs is possible. Nanostructures in general have altered properties compared to those of bulk materials and the same is expected in nanostructured composites. DA - 2008/4/2/ PY - 2008/4/2/ DO - 10.1088/0957-4484/19/13/135603 VL - 19 IS - 13 SP - SN - 1361-6528 ER - TY - JOUR TI - Nearly lattice-matched n, i, and p layers for InGaN p-i-n photodiodes in the 365-500 nm spectral range AU - Berkman, E. A. AU - El-Masry, N. A. AU - Emara, A. AU - Bedair, S. M. T2 - APPLIED PHYSICS LETTERS AB - We report on nearly lattice-matched grown InGaN based p-i-n photodiodes detecting in the 365–500nm range with tunable peak responsivity tailored by the i-layer properties. The growth of lattice matched i- and n-InGaN layer leads to improvement in the device performance. This approach produced photodiodes with zero-bias responsivities up to 0.037A∕W at 426nm, corresponding to 15.5% internal quantum efficiency. The peak responsivity wavelength ranged between 416 and 466nm, the longest reported for III-N photodiodes. The effects of InN content and i-layer thickness on photodiode properties and performance are discussed. DA - 2008/3/10/ PY - 2008/3/10/ DO - 10.1063/1.2896648 VL - 92 IS - 10 SP - SN - 0003-6951 ER - TY - JOUR TI - Nanoceria as antioxidant: Synthesis and biomedical applications AU - Karakoti, A. S. AU - Monteiro-Riviere, N. A. AU - Aggarwal, R. AU - Davis, J. P. AU - Narayan, R. J. AU - Self, W. T. AU - McGinnis, J. AU - Seal, S. T2 - JOM AB - The therapeutic application of nanomaterials has been a focus of numerous studies in the past decade. Due to its unique redox properties, cerium oxide (ceria) is finding widespread use in the treatment of medical disorders caused by the reactive oxygen intermediates (ROI). The radical-scavenging role of ceria nanoparticles (nanoceria) have been established, as well as the autocatalytic ability of nanoceria to regenerate under various environmental conditions. The synthesis of nanoceria in biocompatible media has also been reported along with cell viability in order to determine the potential use of nanoceria in biomedical applications. DA - 2008/3// PY - 2008/3// DO - 10.1007/s11837-008-0029-8 VL - 60 IS - 3 SP - 33-37 SN - 1543-1851 ER - TY - PAT TI - Methods of forming pluralities of capacitors AU - Basceri, C. AU - Sandhu, G. S. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Methods of forming materials AU - Sarigiannis, D. AU - Derderian, G. J. AU - Basceri, C. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Methods of forming capacitor AU - Miller, M. W. AU - Basceri, C. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Methods and apparatus for processing microfeature workpieces; methods for conditioning ALD reaction chambers AU - Beaman, K. L. AU - Weimer, R. A. AU - Breiner, L. D. AU - Ping, E. X. AU - Doan, T. T. AU - Basceri, C. AU - Kubista, D. J. AU - Zheng, L. A. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Method of forming conductive metal silicides by reaction of metal with silicon AU - Basceri, C. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - MIS capacitor and method of formation AU - Basceri, C. AU - Derderian, G. J. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Gallium nitride material transistors and methods associated with the same AU - Nagy, W. H. AU - Borges, R. M. AU - Brown, J. D. AU - Chaudhari, A. D. AU - Cook, J. W. AU - Hanson, A. W. AU - Johnson, J. W. AU - Linthicum, K. J. AU - Piner, E. L. AU - Rajagopal, P. AU - Roberts, J. C. AU - Singhal, S. AU - Therrien, R. J. AU - Vescan, A. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Gallium nitride material structures including substrates and methods associated with the same AU - Piner, E. L. AU - Rajagopal, P. AU - Roberts, J. C. AU - Linthicum, K. J. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Flexible and lithography-compatible copper foil substrates for ferroelectric thin films AU - Laughlin, B. AU - Ihlefeld, J. F. AU - Daniels, Patrick AU - Maria, J. -P. T2 - THIN SOLID FILMS AB - A process has been developed for preparing a low surface roughness copper foil by evaporation and subsequent peel-off of copper metal layers on glass slides. These 15 micron thick substrates exhibited roughness values between 1 and 2 nm root-mean-square (RMS) and 9 nm RMS over 25 μm2 and 100 μm2 analysis areas, respectively. The deposition and crystallization of barium strontium titanate layers were demonstrated on these smoother variant foils. The fully processed dielectric layers exhibited field tunability greater than 5:1, and could withstand fields in excess of 750 kV/cm. High field loss tangents below 0.007 were observed, making these materials excellent candidates for microwave devices. Finally, a process of lamination and contact lithography was used to demonstrate patterning of micron-scale features suitable for microwave circuit element designs. DA - 2008/3/31/ PY - 2008/3/31/ DO - 10.1016/j.tsf.2007.08.093 VL - 516 IS - 10 SP - 3294-3297 SN - 0040-6090 KW - ferroelectric KW - microwave KW - Cu KW - film KW - BST KW - barium strontium titanate ER - TY - JOUR TI - Dipole model explaining high-k/metal gate field effect transistor threshold voltage tuning AU - Kirsch, P. D. AU - Sivasubramani, P. AU - Huang, J. AU - Young, C. D. AU - Quevedo-Lopez, M. A. AU - Wen, H. C. AU - Alshareef, H. AU - Choi, K. AU - Park, C. S. AU - Freeman, K. AU - Hussain, M. M. AU - Bersuker, G. AU - Harris, H. R. AU - Majhi, P. AU - Choi, R. AU - Lysaght, P. AU - Lee, B. H. AU - Tseng, H. -H. AU - Jammy, R. AU - Boescke, T. S. AU - Lichtenwalner, D. J. AU - Jur, J. S. AU - Kingon, A. I. T2 - APPLIED PHYSICS LETTERS AB - An interface dipole model explaining threshold voltage (Vt) tuning in HfSiON gated n-channel field effect transistors (nFETs) is proposed. Vt tuning depends on rare earth (RE) type and diffusion in Si∕SiOx∕HfSiON∕REOx/metal gated nFETs as follows: Sr&lt;Er&lt;Sc+Er&lt;La&lt;Sc&lt;none. This Vt ordering is very similar to the trends in dopant electronegativity (EN) (dipole charge transfer) and ionic radius (r) (dipole separation) expected for a interfacial dipole mechanism. The resulting Vt dependence on RE dopant allows distinction between a dipole model (dependent on EN and r) and an oxygen vacancy model (dependent on valence). DA - 2008/3/3/ PY - 2008/3/3/ DO - 10.1063/1.2890056 VL - 92 IS - 9 SP - SN - 1077-3118 ER - TY - JOUR TI - Dielectric and microstructural properties of barium titanate hafhate thin films AU - Ihlefeld, J. F. AU - Borland, W. J. AU - Maria, J. P. T2 - Thin Solid Films AB - Barium titanate hafnate (BaTi1−xHfxO3, 0 ≤ x ≤ 0.25) thin films have been deposited by a chemical solution method on copper foil substrates. The films were crystallized at 900 °C and in a reducing atmosphere to prevent substrate oxidation. Perovskite phase formation was identified for each composition, accompanied by an increased pseudocubic lattice parameter. Temperature dependent dielectric measurements revealed a decreasing phase transition temperature and peak permittivity with increasing hafnium level. The decrease in permittivity resulted from grain size reduction with increasing hafnium content. Compositions containing 25 mol% barium hafnate display a deviation from Curie–Weiss behavior indicating the onset of relaxor behavior. DA - 2008/// PY - 2008/// DO - 10.1016/j.tsf.2007.08.096 VL - 516 IS - 10 SP - 3162-3166 ER - TY - PAT TI - DRAM constructions and electronic systems AU - Basceri, C. AU - Gealy, F. D. AU - S., Sandhu G. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Cyclic tensile strain increases interactions between human epidermal keratinocytes and quantum dot nanoparticles AU - Rouse, Jillian G. AU - Haslauer, Carla M. AU - Loboa, Elizabeth G. AU - Monteiro-Riviere, Nancy A. T2 - TOXICOLOGY IN VITRO AB - The effects of quantum dots (QD) on cell viability have gained increasing interest due to many recent developments utilizing QD for pharmaceutical and biomedical applications. The potential use of QD nanoparticles as diagnostic, imaging, and drug delivery agents has raised questions about their potential for cytotoxicity. The objective of this study was to investigate the effects of applied strain on QD uptake by human epidermal keratinocytes (HEK). It was hypothesized that introduction of a 10% average strain to cell cultures would increase QD uptake. HEK were seeded at a density of 150,000 cells/mL on collagen-coated Flexcell culture plates (Flexcell Intl.). QD were introduced at a concentration of 3 nM and a 10% average strain was applied to the cells. After 4 h of cyclic strain, the cells were examined for cell viability, QD uptake, and cytokine production. The results indicate that addition of strain results in an increase in cytokine production and QD uptake, resulting in irritation and a negative impact on cell viability. Application of physiological load conditions can increase cell membrane permeability, thereby increasing the concentration of QD nanoparticles in cells. DA - 2008/3// PY - 2008/3// DO - 10.1016/j.tiv.2007.10.010 VL - 22 IS - 2 SP - 491-497 SN - 0887-2333 KW - quantum dot nanoparticles KW - keratinocytes KW - skin KW - tensile strain KW - cellular uptake ER - TY - PAT TI - Constructions comprising hafnium oxide AU - Basceri, C. AU - Gealy, F. D. AU - Sandhu, G. S. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Capacitance transient study of the influence of iron contamination on the electrical characteristics of silicon grain boundaries AU - Lu, J. G. AU - Rozgonyi, G. T2 - Applied Physics Letters DA - 2008/// PY - 2008/// VL - 92 IS - 8 ER - TY - PAT TI - Atomic layer deposition methods AU - Sarigiannis, D. AU - Derderian, G. J. AU - Basceri, C. AU - Sandhu, G. S. AU - Gealy, F. D. AU - Carlson, C. M. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - An evaluation of loose tenon joint strength AU - Aman, R. L. AU - West, H. A. AU - Cormier, D. R. T2 - Forest Products Journal DA - 2008/// PY - 2008/// VL - 58 IS - 3 SP - 61-64 ER - TY - JOUR TI - Self-thickening, cross-slip deformation twinning model AU - Narayan, J. AU - Zhu, Y. T. T2 - Applied Physics Letters AB - We propose a cross-slip deformation twinning model based upon our experimental in situ deformation of Cu–Ge alloys using a transmission electron microscope. During the deformation, Shockley partials are emitted from the grain boundaries, which encounter an obstacle within the grain and split to nucleate deformation twins in the cross slip as well as primary planes. Upon further deformation a thickening process for twins is directly observed. The proposed model provides a dislocation mechanism for the observed simultaneous twin thickening in both the cross-slip and primary planes. The role of the proposed mechanism in the deformation of nanocrystalline materials is discussed. DA - 2008/4/14/ PY - 2008/4/14/ DO - 10.1063/1.2911735 VL - 92 IS - 15 SP - 151908 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2911735 DB - Crossref ER - TY - JOUR TI - Piezoresponse force microscopy studies of switching behavior of ferroelectric capacitors on a 100-ns time scale AU - Gruverman, A. AU - Wu, D. AU - Scott, J. F. T2 - Physical Review Letters DA - 2008/// PY - 2008/// VL - 1 IS - 9 ER - TY - JOUR TI - New deformation twinning mechanism generates zero macroscopic strain in nanocrystalline metals AU - Wu, X. L. AU - Liao, X. Z. AU - Srinivasan, S. G. AU - Zhou, F. AU - Lavernia, E. J. AU - Valiev, R. Z. AU - Zhu, Y. T. T2 - Physical Review Letters DA - 2008/// PY - 2008/// VL - 1 IS - 9 ER - TY - JOUR TI - Model study of electron beam charge compensation for positive secondary ion mass spectrometry using a positive primary ion beam AU - Zhu, Z. M. AU - Stevie, F. A. AU - Griffis, D. P. T2 - Applied Surface Science AB - A new modeling approach has been developed to assist in the SIMS analysis of insulating samples. This approach provides information on the charging phenomena occurring when electron and positive primary ion beams impact a low conductivity material held at a high positive potential. The concept of effective leakage resistance aids in the understanding of the dynamic electrical properties of an insulating sample under dynamic analysis conditions. Modeling of steady state electron beam charge compensation involves investigation of electron injection and charge drift. Using a Monte Carlo program to simulate electron injection and dc conduction calculations to predict charge drift, detailed information regarding charging phenomena can be determined. DA - 2008/// PY - 2008/// DO - 10.1016/j.apsusc.2007.10.008 VL - 254 IS - 9 SP - 2708-2711 ER - TY - JOUR TI - Enhanced dielectric tunability in barium titanate thin films with boron additions AU - Ihlefeld, Jon F. AU - Borland, William J. AU - Maria, Jon-Paul T2 - SCRIPTA MATERIALIA AB - Boron incorporation in 650 nm thick polycrystalline BaTiO3 films results in grain growth and dramatic dielectric response improvements. For levels between 0% and 3%, average grain size is increased from 150 to 200 nm and the maximum permittivity values are nearly doubled, with tunabilities increased to greater than 90% while maintaining high field loss tangents below 0.03. These results demonstrate a pathway for microstructure engineering and property optimization in refractory electroceramic oxide thin films without increasing the thermal budget. DA - 2008/4// PY - 2008/4// DO - 10.1016/j.scriptamat.2007.11.008 VL - 58 IS - 7 SP - 549-552 SN - 1359-6462 KW - dielectrics KW - thin films KW - ferroelectricity KW - grain growth KW - copper ER - TY - JOUR TI - Cellular incorporation into electrospun nanofibers - Retained viability, proliferation, and function in fibroblasts AU - Aalst, John A. AU - Reed, Courtney R. AU - Han, Li AU - Andrady, Tony AU - Hromadka, Michael AU - Bernacki, Susan AU - Kolappa, Kamalkumar AU - Collins, James B. AU - Loboa, Elizabeth G. T2 - ANNALS OF PLASTIC SURGERY AB - Nanofibers are an emerging scaffold for tissue engineering. To date no one has reported cell incorporation into nanofibers. Human foreskin fibroblasts and human adipose-derived adult stem cells (hADAS) were grown to confluence, resuspended in phosphate-buffered saline, and then solubilized in polyvinyl alcohol (PVA). Nanofibers were created using an electrospinning technique across an electric potential of 20 kV. Cell interaction with nanofibers was assessed with optical microscopic imaging and scanning electron microscopy. PVA nanofibers with incorporated cells were then solubilized in phosphate-buffered saline; cell viability was assessed by trypan blue exclusion. Viable cells were allowed to proliferate. Chondrogenesis in fibroblasts was induced with TGF-β1. Both fibroblasts and hADAS survived the electrospinning process and were incorporated into PVA nanofibers. hADAS cell proliferation was negligible; however, fibroblasts proliferated and showed retained ability to undergo chondrogenesis. Cells can be incorporated into nanofibers, with maintained viability, proliferation, and function. DA - 2008/5// PY - 2008/5// DO - 10.1097/SAP.0b013e318168db3e VL - 60 IS - 5 SP - 577-583 SN - 1536-3708 KW - nanofibers KW - fibroblasts KW - adipose-derived adult stem cells KW - electrospinning KW - nanotechnology ER - TY - JOUR TI - Application of the anisotropic bond model to second-harmonic generation from amorphous media AU - Adles, E. J. AU - Aspnes, D. E. T2 - PHYSICAL REVIEW B AB - As a step toward analyzing second-harmonic generation (SHG) from crystalline Si nanospheres in glass, we develop an anisotropic bond model (ABM) that expresses SHG in terms of physically meaningful parameters and provide a detailed understanding of the basic physics of SHG on the atomic scale. Nonlinear-optical (NLO) responses are calculated classically via the four fundamental steps of optics: evaluate the local field at a given bond site, solve the force equation for the acceleration of the charge, calculate the resulting radiation, then superpose the radiation from all charges. Because the emerging NLO signals are orders of magnitude weaker and occur at wavelengths different from that of the pump beam, these steps are independent. Paradoxically, the treatment of NLO is therefore simpler than that of linear optics (LO), where these calculations must be done self-consistently. The ABM goes beyond previous bond models by including the complete set of underlying contributions: retardation (RD), spatial-dispersion (SD), and magnetic (MG) effects, in addition to the anharmonic restoring force acting on the bond charge. Transverse as well as longitudinal motion is also considered. We apply the ABM to obtain analytic expressions for SHG from amorphous materials under Gaussian-beam excitation. These materials represent an interesting test case not only because they are ubiquitous but also because the anharmonic-force contribution that dominates the SHG response of crystalline materials and ordered interfaces vanishes by symmetry. The remaining contributions, and hence the SHG signals, are entirely functions of the LO response and beam geometry, so the only new information available is the anisotropy of the LO response at the bond level. The RD, SD, and MG contributions are all of the same order of magnitude, so none can be ignored. Diffraction is important in determining not only the pattern of the emerging beam but also the phases and amplitudes of the different terms. The plane-wave expansion that gives rise to electric quadrupole magnetic dipole effects in LO appears here as retardation. Using the paraxial-ray approximation, we reduce the results to the isotropic case in two limits, that where the linear restoring force dominates (glasses) and that where it is absent (metals). Both forward- and backscattering geometries are discussed. Estimated signal strengths and conversion efficiencies for fused silica appear to be in general agreement with data where available. Predictions that allow additional critical tests of these results are made. DA - 2008/4// PY - 2008/4// DO - 10.1103/physrevb.77.165102 VL - 77 IS - 16 SP - SN - 1098-0121 ER - TY - JOUR TI - Tunneling entity in different injection regimes of InGaN light emitting diodes AU - Reynolds, C. L., Jr. AU - Patel, A. T2 - JOURNAL OF APPLIED PHYSICS AB - The forward I-V characteristics of InGaN-based light emitting diodes heteroepitaxially grown have previously been shown to be dominated by tunneling over a wide range of bias, as indicated by unrealistic values for the ideality factor. Comparison of the electrical characteristics in different bias regimes for InGaN light emitting diodes (LEDs) to expressions for the tunneling current enables one to achieve an understanding of the tunneling entities involved. At low bias for LEDs grown on sapphire, data are consistent with electron tunneling to deep levels in the vicinity of mixed/screw dislocations and are characterized by an energy near 200meV. This component is absent for those devices homoepitaxially grown. In the intermediate bias regime, LEDs both heteroepitaxially and homoepitaxially grown exhibit a tunneling component that is proposed to be associated with the heavy hole tunneling via intermediate states and to have a characteristic energy near 80meV. DA - 2008/4/15/ PY - 2008/4/15/ DO - 10.1063/1.2906326 VL - 103 IS - 8 SP - SN - 1089-7550 ER - TY - JOUR TI - Thermal stability, mechanical and electrical properties of nanocrystalline Cu3Ge AU - Darling, Kris A. AU - Guduru, R.K. AU - Reynolds, C. Lewis, Jr AU - Bhosle, Vikram M. AU - Chan, Ryan N. AU - Scattergood, Ronald O. AU - Koch, Carl C. AU - Narayan, J. AU - Aboelfotoh, M.O. T2 - Intermetallics AB - The intermetallic ɛ1 compound Cu3Ge was produced through a mechanical alloying procedure that enables the formation of a nanograined microstructure. There is a dependence of grain size (20–11 nm) on milling conditions. The microstructure remained very stable even at temperatures up to 500 °C for 5 h which is a minimum of 76% of the melting temperature. The materials produced by these methods were in the form of powders with particle size ranging from 200 nm to 10 μm. The morphology of the particles varied with the largest being rough and irregular and the smallest being spherical. Preliminary resistivity measurements showed low resistivity, 8.8 μΩ cm, which is comparable to that previously reported for thin films with grain sizes thousands of times larger. Nanoindentation was also performed, yielding an elastic modulus of ∼110 GPa. DA - 2008/3// PY - 2008/3// DO - 10.1016/j.intermet.2007.11.005 VL - 16 IS - 3 SP - 378-383 J2 - Intermetallics LA - en OP - SN - 0966-9795 UR - http://dx.doi.org/10.1016/j.intermet.2007.11.005 DB - Crossref KW - nanostructured intermetallics KW - thermal stability KW - mechanical properties at ambient temperatures KW - electrical resistance and other electrical properties KW - mechanical alloying and milling ER - TY - JOUR TI - Overlayer effects in the critical-point analysis of ellipsometric spectra: Application to InxGa1-xAs alloys AU - Ghong, T. H. AU - Kim, T. J. AU - Jung, Y. W. AU - Kim, Y. D. AU - Aspnes, D. E. T2 - JOURNAL OF APPLIED PHYSICS AB - We investigate the effect of incomplete removal of semiconductor overlayers on critical-point (CP) parameters determined from the analysis of ellipsometric spectra. An approximate analytic expression shows that CP energies and broadening parameters should be relatively unaffected for isolated CPs if the dielectric response of the overlayer varies slowly with energy. The results are confirmed by model calculations for InAs, which show that the energies of the E1 and E1+Δ1 CP structures that are commonly used for compositional analysis of semiconductor alloys are relatively unaffected. We also analyze overlayer-removal data for a series of InxGa1−xAs alloy samples. Consistent with the above, the amplitudes and phases are affected significantly for all CPs, while the energies of the well-separated E1 and E1+Δ1 transitions are relatively invariant. The results show that accurate values of composition can be obtained from the analysis of the E1 and E1+Δ1 CP structures, even if complete removal of overlayers is not achieved. DA - 2008/4/1/ PY - 2008/4/1/ DO - 10.1063/1.2902502 VL - 103 IS - 7 SP - SN - 1089-7550 ER - TY - JOUR TI - Optical properties of InxAl1-xAs alloy films AU - Yoon, J. J. AU - Ghong, T. H. AU - Byun, J. S. AU - Kim, Y. D. AU - Aspnes, D. E. AU - Kim, H. J. AU - Chang, Y. C. AU - Song, J. D. T2 - APPLIED PHYSICS LETTERS AB - Pseudodielectric functions ⟨ε⟩ of InxAl1−xAs ternary alloy films were determined from 1.5to6.0eV by spectroscopic ellipsometry. We minimized overlayer effects by performing wet-chemical etching to more accurately determine intrinsic bulk dielectric responses. Energies of the E1, E1+Δ1, E0′, E2, E2+Δ2 and E2′ critical points (CPs) were identified by band structure calculations of the linear augmented Slater-type orbital method. These calculations also showed a crossing of the E0′ and E2 CP structures with increasing In composition and a new saddle point in the AlAs band structure. DA - 2008/4/14/ PY - 2008/4/14/ DO - 10.1063/1.2909546 VL - 92 IS - 15 SP - SN - 1077-3118 ER - TY - PAT TI - Method of manufacturing gallium nitride based high-electron mobility devices AU - Harris, C. AU - Gehrke, T. AU - Weeks, T. W. AU - Basceri, C. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Jetting and detonation initiation in shock induced collapse of nanometer-scale voids AU - Shi, Yunfeng AU - Brenner, Donald W. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - Molecular dynamics simulations have been used to characterize the dynamics of the shock-induced asymmetric collapse of nanometer-scale voids in cubane nitrogen and to characterize how this dynamics couples with local chemistry to increase the shock sensitivity relative to homogeneous initiation. Mesoscopic-scale features of the void collapse correspond well to experimentally observed features of micrometer-scale bubble collapse, including a transition from single to double jetting with an increasing transverse void length. An analytic model is developed for the enhanced shock sensitivity as a function of void size and shape that reproduces the simulation results. At the atomic level, the simulations show vibrational up-pumping of molecules in the jet front because of collisions with the downstream wall followed by bi-molecular reactive dynamics from continued jet impact that triggers the onset of initiation. These results provide important new insights into the coupling of hydrodynamic void collapse and the enhanced shock sensitivity of energetic materials. DA - 2008/4/24/ PY - 2008/4/24/ DO - 10.1021/jp7119735 VL - 112 IS - 16 SP - 6263-6270 SN - 1932-7455 ER - TY - JOUR TI - Hot sputtering of barium strontium titanate on nickel foils AU - Aygun, Seymen M. AU - Daniels, Patrick AU - Borland, William AU - Maria, Jon-Paul T2 - JOURNAL OF APPLIED PHYSICS AB - The relationships linking temperature and voltage dependent dielectric response, grain size, and thermal budget during synthesis are illustrated. In doing so, it was found that maximizing thermal budgets within experimental bounds leads to electrical properties comparable to the best literature reports irrespective of the processing technique or microstructure. The optimal film properties include a bulk transition temperature, a room temperature permittivity of 1800, a voltage tuning ratio of 10:1 at 450 kV/cm, and a loss tangent less than 1.5% at 450 kV/cm. The sample set illustrates the well-known relationship between permittivity and crystal dimension, and the onset of a transition temperature shifts at very fine grain sizes. A brick wall model incorporating a high permittivity grain and a low permittivity grain boundary is used to interpret the dielectric data. However, the data show that high permittivity and tunability values can be achieved at grain sizes or film thicknesses that many reports associate with dramatic reductions in the dielectric response. These differences are discussed in terms of crystal quality and maximum processing temperature. The results collectively suggest that scaling effects in ferroelectric thin films are in many cases the result of low thermal budgets and the consequently high degree of structural imperfection and are not from the existence of low permittivity phases at the dielectric-electrode interface. DA - 2008/4/15/ PY - 2008/4/15/ DO - 10.1063/1.2909920 VL - 103 IS - 8 SP - SN - 0021-8979 ER - TY - PAT TI - Gallium nitride based high-electron mobility devices AU - Harris, C. AU - Gehrke, T. AU - Weeks, T. W. AU - Basceri, C. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Extrinsic scaling effects on the dielectric response of ferroelectric thin films AU - Ihlefeld, Jon F. AU - Vodnick, Aaron M. AU - Baker, Shefford P. AU - Borland, William J. AU - Maria, Jon-Paul T2 - JOURNAL OF APPLIED PHYSICS AB - Scaling effects in polycrystalline ferroelectric thin films were investigated by preparing barium titanate in a manner that maintained constant composition and film thickness while allowing systematically increased grain size and crystalline coherence. The average grain dimensions ranged from 60to110nm, and temperature dependence of permittivity analysis revealed diffuse phase transitions in all cases. Maximum permittivity values ranged from 380 to 2040 for the smallest to largest sizes, respectively. Dielectric hysteresis is evident at room temperature for all materials, indicating stability of the ferroelectric phase. Comparison of permittivity values at high electric fields indicates that the intrinsic dielectric response is identical and microstructural artifacts likely have a minimal influence on film properties across the sample series. Permittivity values, however, are substantially smaller than those reported for bulk material with similar grain dimensions. X-ray line broadening measurements were taken for the grain size series at the Cornell High Energy Synchrotron Source (CHESS), which revealed coherent scattering dimensions substantially smaller than the microscopy-determined grain size. Collectively these data sets suggest that permittivity values are influenced not only by grain size but also by the mosaic structure existing within each grain, and that thin film thermal budgets, which are several hundred degrees lower than used for bulk processing, are responsible for reduced crystalline coherence, and likely the origin of degraded electromechanical response in thin film ferroelectrics. DA - 2008/4/1/ PY - 2008/4/1/ DO - 10.1063/1.2903211 VL - 103 IS - 7 SP - SN - 1089-7550 ER - TY - JOUR TI - Electrical and photoelectrical characterization of undoped and S-doped nanocrystalline diamond films AU - Kulkarni, P. AU - Porter, L. M. AU - Koeck, F. A. M. AU - Tang, Y. -J. AU - Nemanich, R. J. T2 - JOURNAL OF APPLIED PHYSICS AB - Nanocrystalline diamond (NCD) films are being intensively researched for a variety of potential applications, such as optical windows, electrochemical electrodes, and electron emitting surfaces for field emission displays. In this study Zr, Ti, Cu, and Pt on intrinsic and lightly sulfur-doped (n-type) NCD films were electrically and photoelectrically characterized. Intrinsic and sulfur-doped NCD films were synthesized on 1in. diameter quartz and silicon substrates by microwave plasma assisted chemical vapor deposition. All metals showed linear (Ohmic) current-voltage characteristics in the as-deposited state. The Schottky barrier heights (ΦB) at the metal-film interface were investigated using x-ray and ultraviolet photoelectron spectroscopies. The undoped NCD films exhibited a negative electron affinity and a band gap of 5.0±0.4eV. The ΦB were calculated based on this band gap measurement and the consistent indication from Hall measurements that the films are n-type. The ΦB values were calculated from shifts in the core-level (C1s) peaks immediately obtained before and after in situ, successive metal depositions. The ΦB values for Zr, Ti, and Pt on undoped films were calculated to be 3.3, 3.2, and 3.7eV, respectively. The S-doped films also showed increasing ΦB with metal work functions: 3.0, 3.1, and 3.4eV for Zr, Ti, and Pt, respectively. In general accordance with the barrier height trends, the specific contact resistivity (ρc) values increased with the metal work functions for both undoped and S-doped films. For the undoped films ρc increased from 3×10−5Ωcm2 for Zr to 6.4×10−3Ωcm2 for Pt. The ρc values for the S-doped films were approximately two orders of magnitude lower than those for the undoped films: 3.5×10−7–4.5×10−5Ωcm2 for Zr and Pt, respectively. The Hall-effect measurements indicated that the average sheet resistivity and carrier concentration values were 0.16 and 3.5×1018cm−3 for the undoped films and 0.15Ωcm and 4.9×1019cm−3 for the S-doped films. DA - 2008/4/15/ PY - 2008/4/15/ DO - 10.1063/1.2908884 VL - 103 IS - 8 SP - SN - 1089-7550 ER - TY - JOUR TI - Deep level transient spectroscopy and capacitance-voltage study of dislocations and associated defects in SiGe/Si heterostructures AU - Lu, J. G. AU - Park, Y. K. AU - Rozgonyi, G. A. T2 - Journal of Applied Physics DA - 2008/// PY - 2008/// VL - 103 IS - 7 ER - TY - PAT TI - Normal incidence rotating compensator ellipsometer AU - Aspnes, D. E. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Effect of substrate temperature on mechanical properties of calcium phosphate coatings AU - Blalock, Travis L. AU - Bai, Xiao AU - Narayan, Roger AU - Rabiei, Afsaneh T2 - JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART B-APPLIED BIOMATERIALS AB - The effect of substrate temperature and processing parameters on mechanical properties of nanoscale calcium phosphate coatings are being studied in order to refine the processing technique for Functionally Graded Hydroxyapatite (FGHA) coatings. Coatings were deposited on titanium substrates with a set substrate temperature of 450, 550, 650, or 750 degrees C in an Ion Beam Assisted Deposition (IBAD) system using a sintered hydroxyapatite (HA) target. Mechanical properties of the coatings deposited with a set substrate temperature such as, bonding/adhesion strength to the substrate, nanohardness, and Young's Modulus as well as coating thickness were evaluated and compared with commercial plasma spray HA coatings. It is concluded that depositing FGHA coatings would better be started at 550-650 degrees C to maintain superior properties of the film at the interface. It can also be concluded that the residual stresses caused by different Coefficient of Thermal Expansions (CTEs) between the substrate and coatings are not the only factor controlling the bonding strength and mechanical properties of these samples. Other parameters such as the nature of the interface layers and their bonding to each other as well as the density and grain structure of the coatings must be taken into consideration for an appropriate evaluation of mechanical properties of calcium phosphate coatings deposited on heated substrate. DA - 2008/4// PY - 2008/4// DO - 10.1002/jbm.b.30917 VL - 85B IS - 1 SP - 60-67 SN - 1552-4981 ER - TY - JOUR TI - Effect of an applied electric field on the flow stress of ultrafine-grained 2.5Y-TZP at high temperatures AU - Conrad, H. AU - Yang, Di AU - Becher, P. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Application of a dc electric field (E = 46 V/cm) during the tensile deformation of an ultrafine-grained 2.5Y-TZP (d = 350 nm) at 1450 °C resulted in a significant reduction in the flow stress σ, which reversed upon removal of the field. At strains ϵ ≤ 0.6, the reduction in flow stress ΔσE consisted of two components: (a) a rapid initial decrease in stress (ΔσE*) due to the effect of the field on the deformation mechanism(s) and (b) a longer-time decrease in stress (ΔσT) due to Joule heating, giving ΔσE=ΔσE*+ΔσT. At ϵ > 0.6, an additional contribution (ΔσEstr) occurred, which was attributed to a change in defect structure, e.g., grain growth and cavitation. It was concluded that the rate-controlling mechanism in the present tests is grain boundary sliding accommodated by lattice diffusion of the Zr ions with a threshold stress σo, giving an acting effective stress σe = σ − σo. It was determined for this case that ΔσE* contained reductions in both the effective stress (Δσe,E*) and in the threshold stress (Δσo,E). Analysis of the behavior in terms of an electrochemical potential for vacancy formation showed that Δσe,E* and Δσo,E are related to changes in the electric field potential pertaining to the space charge at the grain boundaries. The calculated width of the space charge region acted on by the electric field was 3–5 nm in the temperature range of 1450–1550 °C. DA - 2008/3/25/ PY - 2008/3/25/ DO - 10.1016/j.msea.2007.05.057 VL - 477 IS - 1-2 SP - 358-365 SN - 1873-4936 KW - zirconia KW - electric field KW - space charge KW - threshold stress KW - vacancies ER - TY - JOUR TI - Applications of structural optimization in direct metal fabrication AU - Cansizoglu, Omer AU - Harrysson, Ola L. A. AU - West, Harvey A., II AU - Cormier, Denis R. AU - Mahale, Tushar T2 - RAPID PROTOTYPING JOURNAL AB - Purpose Optimization techniques can be used to design geometrically complex components with a wide variety of optimization criteria. However, such components have been very difficult and costly to produce. Layered fabrication technologies such as electron beam melting (EBM) open up new possibilities though. This paper seeks to investigate the integration of structural optimization and direct metal fabrication process. Design/methodology/approach Mesh structures were designed, and optimization problems were defined to improve structural performance. Finite element analysis code in conjunction with nonlinear optimization routines were used in MATLAB. Element data were extracted from an STL‐file, and output structures from the optimization routine were manufactured using an EBM machine. Original and optimized structures were tested and compared. Findings There were discrepancies between the performance of the theoretical structures and the physical EBM structures due to the layered fabrication approach. A scaling factor was developed to account for the effect of layering on the material properties. Practical implications Structural optimization can be used to improve the performance of a design, and direct fabrication technologies can be used to realise these structures. However, designers must realize that fabricated structures are not identical to idealized CAD structures, hence material properties much be adjusted accordingly. Originality/value Integration of structural optimization and direct metal fabrication was reported in the paper. It shows the process from design through manufacturing with integrated analysis. DA - 2008/// PY - 2008/// DO - 10.1108/13552540810862082 VL - 14 IS - 2 SP - 114-122 SN - 1355-2546 KW - rapid prototypes KW - optimization techniques ER - TY - JOUR TI - High temperature stability of Hf-based gate dielectric stacks with rare-earth oxide layers for threshold voltage control AU - LeBeau, James M. AU - Jur, Jesse S. AU - Lichtenwalner, Daniel J. AU - Craft, H. Spalding AU - Maria, Jon-Paul AU - Kingon, Angus I. AU - Klenov, Dmitri O. AU - Cagnon, Joël AU - Stemmer, Susanne T2 - Applied Physics Letters AB - The thermal stability of DyOx∕HfSiON and HoOx∕HfSiON gate dielectric stacks on silicon was studied by scanning transmission electron microscopy techniques and correlated with their electrical characteristics. Intermixing of the rare-earth elements with the HfSiON was observed, but there was no diffusion into the interfacial SiO2. Rapid thermal annealing (1000°C) produced little detectable change in the concentration profile of the rare-earth elements but caused thinning of the interfacial SiO2 layer along with a corresponding increase in the rare-earth oxide layer thickness. These reactions could be explained with oxygen deficiency in the rare-earth oxide layer and its greater thermodynamic stability relative to SiO2. Negative flat band voltage shifts were observed relative to a control sample with no DyOx or HoOx. Mechanisms by which the observed microstructure changes could give rise to negative flatband voltage shifts are discussed. DA - 2008/3/17/ PY - 2008/3/17/ DO - 10.1063/1.2901036 VL - 92 IS - 11 SP - 112912 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2901036 DB - Crossref ER - TY - JOUR TI - Effect of platinum on the oxide-to-metal adhesion in thermal barrier coating systems AU - Tawancy, H. M. AU - Ui-Hamid, A. AU - Abbas, N. M. AU - Aboelfotoh, M. O. T2 - JOURNAL OF MATERIALS SCIENCE DA - 2008/5// PY - 2008/5// DO - 10.1007/s10853-007-2130-8 VL - 43 IS - 9 SP - 2978-2989 SN - 0022-2461 ER - TY - JOUR TI - Creep behavior of niobium-modified zirconium alloys AU - Charit, I. AU - Murty, K. L. T2 - JOURNAL OF NUCLEAR MATERIALS AB - Zirconium (Zr) alloys remain as the main cladding materials in most water reactors. Historically, a series of Zircaloys were developed, and two versions, Zircaloy-2 and -4, are still employed in many reactors. The recent trend is to use the Nb-modified zirconium alloys as the Nb addition improves cladding performance in various ways, most significant being superior long term corrosion resistance. Hence, new alloys with Nb additions have recently been developed, such as Zirlo™2 and M5™3. Although it is known that creep properties improve, there have been very few data available to precisely evaluate the creep characteristics of new commercial alloys. However, the creep behavior of many Nb-modified zirconium alloys has been studied in several occasions. In this study, we have collected the creep data of these Nb-modified alloys from the open literature as well as our own study over a wide range of stresses and temperatures. The data have been compared with those of conventional Zr and Zircaloys to determine the exact role Nb plays. It has been argued that Nb-modified zirconium alloys would behave as Class-A alloys (stress exponent of 3) with the Nb atoms forming solute atmospheres around dislocations and thus, impeding dislocation glide under suitable conditions. On the other hand, zirconium and Zircaloys behave as Class-M alloys with a stress exponent of ⩾4, attesting to the dislocation climb-controlled deformation mode. DA - 2008/3/15/ PY - 2008/3/15/ DO - 10.1016/j.jnucmat.2007.08.019 VL - 374 IS - 3 SP - 354-363 SN - 0022-3115 ER - TY - JOUR TI - Three-dimensional geometry of nanometer-scale AlN pits: A new template for quantum dots? AU - Liu, F. D. AU - Collazo, Ramon AU - Mita, S. AU - Sitar, Z. AU - Duscher, G. T2 - Advanced Materials AB - The exact 3D geometry of nanometer-scale AlN pits is determined by Z-contrast imaging. The figure shows the 3D geometry of an AlN nano-pit and its corresponding GaN quantum dot. An atomic-resolution Z-contrast image is displayed in false color to clearly show the Z-contrast of the image, while the other panel displays a schematic 3D view. DA - 2008/// PY - 2008/// DO - 10.1002/adma.200701288 VL - 20 IS - 1 SP - 134- ER - TY - JOUR TI - The influence of substrate polarity on the structural quality of InN layers grown by high-pressure chemical vapor deposition AU - Dietz, N. AU - Alevli, M. AU - Atalay, R. AU - Durkaya, G. AU - Collazo, R. AU - Tweedie, J. AU - Mita, S. AU - Sitar, Z. T2 - APPLIED PHYSICS LETTERS AB - The influence of substrate polarity on the properties of InN layers grown by high-pressure chemical vapor deposition has been studied. The 2Θ-ω x-ray diffraction scans on InN layers deposited on polar GaN epilayers revealed single-phase InN(0002) with a full width at half maximum (FWHM) of around 200arcsec. InN layers grown on N-polar GaN exhibit larger FWHMs. Rocking curve analysis confirmed single-phase InN for both growth polarities, with FWHM values for ω-RC(002) at 2080arcsec for InN grown on Ga-polar templates. The A1(LO) Raman mode analysis shows higher free carrier concentrations in InN grown on N-polar templates, indicating that polarity affects the incorporation of impurities. DA - 2008/1/28/ PY - 2008/1/28/ DO - 10.1063/1.2840192 VL - 92 IS - 4 SP - SN - 0003-6951 ER - TY - JOUR TI - Magnetic properties of epitaxial oxide heterostructures AU - Ramachandran, S. AU - Prater, J. T. AU - Sudhakar, N. AU - Kumar, D. AU - Narayan, J. T2 - SOLID STATE COMMUNICATIONS AB - Diluted Magnetic Semiconductors (DMS) are of great interest as injection sources for spin-polarized currents into semiconductors. Epitaxial devices have been synthesized with an intermediate spacer layer of the same semiconductor (zinc oxide, ZnO) used to produce the DMS material (ZnCoO) ensuring a homoepitaxial junction to help reduce the interface states and conduction mismatch. We observe a large magnetoresistance of about 32% in the devices at low temperatures. The present work suggests that spin polarized transport could be achieved with DMS materials acting as the source of injected spins into a non-magnetic host. DA - 2008/1// PY - 2008/1// DO - 10.1016/j.ssc.2007.10.005 VL - 145 IS - 1-2 SP - 18-22 SN - 1879-2766 KW - spintronics : devices exploiting spin polarized transport or integrated magnetic fields KW - magnetic semiconductors KW - magnetotransport phenomena KW - spin transport through interfaces ER - TY - JOUR TI - Importance of solution chemistry in preparing sol-gel PZT thin films directly on copper surfaces AU - Losego, Mark D. AU - Ihlefeld, Jon F. AU - Maria, Jon-Paul T2 - CHEMISTRY OF MATERIALS AB - The ferroelectric material lead zirconate titanate (PZT) has traditionally been considered incompatible with base metal technology because PbO volatility makes conventional thermodynamic equilibrium processing impractical. However, by strategically designing solution chemistry and processing conditions to avoid interfacial reaction, chemical-solution-deposited PZT films can be prepared on copper surfaces without oxidizing the base metal or cracking the oxide film. A limited set of thermal and atmospheric processing conditions to kinetically maintain an unoxidized copper substrate are available and not necessarily optimal for processing sol–gel films. Solutions processed within these confined conditions must form gels with sufficiently reduced organic content and properly consolidated gel networks such that phase-pure and crack-free ceramic films can be crystallized. The current work explores three solution chemistries that use different chelating ligands: alkanolamines, acetylactone, and acetic acid. It is found that the alkanolamine solution frustrates perovskite formation and is prone to cracking under processing conditions compatible with the copper substrate. The introduction of water vapor into the processing atmosphere is moderately successful in resolving these issues. Using a more volatile chelating ligand (acetylacetone or acetic acid) shifts the thermal process window nearer a copper-compatible regime. Because of its weaker chelation strength, acetic acid solutions are most compatible with the processing constraints required for copper substrate compatibility. DA - 2008/1/8/ PY - 2008/1/8/ DO - 10.1021/cm070999q VL - 20 IS - 1 SP - 303-307 SN - 0897-4756 ER - TY - JOUR TI - Stimulated emission and lasing from an Al0.13Ga0.87N/GaN double heterostructure grown on a silicon substrate AU - Al-Ajmi, F. S. AU - Kolbas, R. M. AU - Roberts, J. C. AU - Rajagopal, P. AU - Cook, J. W. AU - Piner, E. L. AU - Linthicum, K. J. T2 - Applied Physics Letters DA - 2008/// PY - 2008/// VL - 92 IS - 2 ER - TY - JOUR TI - Investigation of basic crystal hardening inequalities in a range of stable lattice orientations in (110) channel die compression AU - Havner, Kerry S. T2 - INTERNATIONAL JOURNAL OF PLASTICITY AB - Abstract The fcc slip-systems hardening inequalities given in [Havner, K.S., 2005. On lattice and material-frame rotations and crystal hardening in high-symmetry axial loading. Philos. Mag. 85 (25), 2861–2894] are investigated in (1 1 0) channel die compression for the 35.26° range of lateral constraint directions from ( 1 1 ¯ 1 ¯ ) (the ‘brass’ orientation) to ( 1 1 ¯ 0 ) (the ‘Goss’ orientation). It is established analytically that the inequalities uniquely predict lattice stability and finite shearing about the (1 1 0) load axis, consistent with experiments in this range. An analysis of the continuation of lattice stability to large deformations leads to a critical strain at which the lattice could theoretically, but not necessarily, lose stability. DA - 2008/// PY - 2008/// DO - 10.1016/j.ijplas.2007.02.002 VL - 24 IS - 1 SP - 74-88 SN - 0749-6419 KW - Fcc crystals KW - channel die compression KW - slip-systems hardening inequalities KW - lattice stability ER - TY - JOUR TI - Epitaxial growth of the metastable phase ytterbium monoxide on gallium nitride surfaces AU - Losego, Mark D. AU - Mita, Seiji AU - Collazo, Ramon AU - Sitar, Zlatko AU - Maria, Jon-Paul T2 - JOURNAL OF CRYSTAL GROWTH AB - Molecular beam deposition systems allow for unparalleled control of film composition and structure. This article addresses the capacity for controlling metal and oxidant fluxes in the Yb/O2 system to access the metastable phase ytterbium monoxide (YbO). Experiments exploring the growth of polycrystalline YbOx films by molecular beam deposition demonstrate that a 2:1 molar ratio of Yb:O2 fluxes is necessary to achieve preferential growth of the divalent oxide. Applying similar deposition conditions to a (0 0 1) GaN surface leads to the growth of epitaxial (1 1 1) YbO films. Similar to other rocksalt oxides grown on GaN surfaces, YbO films display a 3D growth mechanism that leads to a grainy morphology with crystallites of 50 nm lateral dimensions. Rocking curves in ω and φ have full-width half-maximum values of 1.77° and 4.1°, respectively; further improvements in crystal quality appear to be limited by the thermal stability of the YbO phase. DA - 2008/1/4/ PY - 2008/1/4/ DO - 10.1016/j.jcrysgro.2007.10.002 VL - 310 IS - 1 SP - 51-56 SN - 0022-0248 KW - phase equilibria KW - molecular beam epitaxy KW - metastable compounds KW - oxides KW - rare earth compounds KW - ytterbium monoxide ER - TY - JOUR TI - Effect of an alternating current electric field on the plastic deformation of ultrafine-grained 3Y-TZP at 1400 degrees C and 1500 degrees C AU - Conrad, Hans AU - Yang, Di T2 - METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE DA - 2008/2// PY - 2008/2// DO - 10.1007/s11661-007-9396-y VL - 39A IS - 2 SP - 272-278 SN - 1073-5623 ER - TY - JOUR TI - Nanostructuring of TiNi alloy by SPD processing for advanced properties AU - Valiev, Ruslan AU - Gunderov, Dmitry AU - Prokofiev, Egor AU - Pushin, Vladimir AU - Zhu, Yuntian T2 - MATERIALS TRANSACTIONS AB - Ultrafine-grained (UFG) alloy Ti49.4Ni50.6 possessing both nano- as well as submicrocrystalline structure has been successfully produced using two techniques of severe plastic deformation (SPD) processing: high pressure torsion and equal channel angular pressing. The features of microstructure, martensitic transformation and deformation behavior of the UFG alloy have been studied in details. The effects of grain size on the mechanical and functional properties of the alloy are discussed. DA - 2008/1// PY - 2008/1// DO - 10.2320/matertrans.ME200722 VL - 49 IS - 1 SP - 97-101 SN - 1347-5320 KW - severe plastic deformation KW - ultrafine grains KW - mechanical properties KW - shape memory titanium nickel alloy ER - TY - JOUR TI - Low energy electron-excited nanoscale luminescence spectroscopy studies of intrinsic defects in HfO2 and SiO2-HfO2-SiO2-Si stacks AU - Strzhemechny, Y. M. AU - Bataiev, M. AU - Tumakha, S. P. AU - Goss, S. H. AU - Hinkle, C. L. AU - Fulton, C. C. AU - Lucovsky, G. AU - Brillson, L. J. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 2008/// PY - 2008/// VL - 26 IS - 1 SP - 232-243 ER - TY - JOUR TI - Defect chemistry of nano-grained barium titanate films AU - Ihlefeld, Jon F. AU - Losego, Mark D. AU - Collazo, Ramon AU - Borland, William J. AU - Maria, Jon-Paul T2 - JOURNAL OF MATERIALS SCIENCE DA - 2008/1// PY - 2008/1// DO - 10.1007/s10853-007-2135-3 VL - 43 IS - 1 SP - 38-42 SN - 1573-4803 ER - TY - JOUR TI - Bond constraint theory and the quest for the glass computer AU - Agarwal, S. C. AU - Paesler, M. A. AU - Baker, D. A. AU - Taylor, P. C. AU - Lucovsky, G. AU - Edwards, A. T2 - PRAMANA-JOURNAL OF PHYSICS DA - 2008/2// PY - 2008/2// DO - 10.1007/s12043-008-0043-y VL - 70 IS - 2 SP - 245-254 SN - 0973-7111 KW - switching KW - chalcogenide glass KW - bond constraint theory ER - TY - JOUR TI - Kinetics of Ga and In desorption from (7x7)Si(111) and (3x3)6H-SiC(0001) surfaces AU - King, S. W. AU - Davis, R. F. AU - Nemanich, R. J. T2 - SURFACE SCIENCE AB - The desorption characteristics of Ga and In on (7 × 7) Si(1 1 1) and (3 × 3) 6H-SiC(0 0 0 1) surfaces have been determined using temperature programmed desorption. Two peaks were observed for desorption of a 1.5 ± 0.25 monolayer of Ga from the latter surface. The peak at Tmax = 670 °C exhibited zeroth order kinetics; the activation energy and pre-exponential were determined to be 2.6 ± 0.1 eV and 6 × 1027 ± 0.5 atom/cm2 s, respectively. The peak at Tmax = 535 °C exhibited first order desorption kinetics with an activation energy and pre-exponential of 6.2 ± 0.3 eV and 7 × 1021 ± 2 s−1, respectively. In contrast, only zeroth order kinetics and a lower activation energy of 2.0 ± 0.1 eV were determined for desorption of a 1.5 ± 0.25 monolayer of Ga from (7 × 7) Si(1 1 1). The values of these results in tandem with those of related studies of desorption from Si and SiC surfaces indicate that the low and high temperature Ga peaks from SiC are due to desorption from either a wetting layer or adatom sites and from Ga islands, respectively. The difference in desorption activation energies for Ga on Si(1 1 1) and on 6H-SiC(0 0 0 1) surfaces is attributed to differences in lattice matching of Ga to these surfaces. By contrast, only multilayer desorption was observed for 4 ± 1 monolayer of In on SiC(0 0 0 1). The zeroth order desorption activation energy and pre-exponential were 2.4 ± 0.1 eV and 6 × 1027±0.5 atom/cm2 s; they are consistent with the heat of sublimation (2.45–2.5 eV) for liquid In. DA - 2008/1/15/ PY - 2008/1/15/ DO - 10.1016/j.susc.2007.10.034 VL - 602 IS - 2 SP - 405-415 SN - 1879-2758 KW - silicon carbide KW - gallium KW - indium KW - temperature programmed desorption KW - kinetics ER -