TY - CHAP TI - Kinetics of charge generation during formation of Hf and Zr silicate dielectrics AU - Gougousi, T AU - Kelly, MJ AU - Parsons, GN AU - King, TJ AU - Yu, B AU - Lander, RJP AU - Saito, S T2 - Comos Front-End Materials and Process Technology PY - 2003/// VL - 765 SP - 79-84 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000186232900011&KeyUID=WOS:000186232900011 ER - TY - JOUR TI - Vapor-liquid-solid growth of silicon-germanium nanowires AU - Lew, KK AU - Pan, L AU - Dickey, EC AU - Redwing, JM T2 - Advanced Materials AB - SiGe alloy nanowires (see Figure) have been fabricated using vapor–liquid–solid (VLS) growth with silane (SiH 4 ) and germane (GeH 4 ) gas sources. Growth conditions have been identified that produce nanowires with homogeneous alloy composition with negligible Ge coating on the wire surface. The Ge composition in the nanowire can be controlled by varying the inlet GeH 4 /(GeH 4 + SiH 4 ) gas ratio. DA - 2003/// PY - 2003/// DO - 10.1002/adma.200306035 VL - 15 IS - 24 SP - 2073-+ UR - https://app.dimensions.ai/details/publication/pub.1033138643 ER - TY - CONF TI - Grain boundary segregation in titanium dioxide: Evaluation of relative driving forces for segregation AU - Wang, QL AU - Lian, GD AU - Dickey, EC C2 - 2003/// C3 - MRS Online Proceedings Library DA - 2003/// VL - 751 SP - 179-190 ER - TY - CONF TI - Direct synthesis of silicon nanowires using silane and molten gallium AU - Sharma, S AU - Sunkara, MK C2 - 2003/// C3 - MRS Online Proceedings Library DA - 2003/// VL - 737 SP - 615-620 ER - TY - CONF TI - Insights into degradation mechanisms and vacancy ordering in BaTiO 3 AU - Yang, GY AU - Dickey, EC AU - Randall, CA AB - Journal Article Insights into Degradation Mechanisms and Vacancy Ordering in BaTiO3 Get access GY Yang, GY Yang Center for Dielectric Studies/Materials Research Institute Search for other works by this author on: Oxford Academic Google Scholar EC Dickey, EC Dickey Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 Search for other works by this author on: Oxford Academic Google Scholar CA Randall CA Randall Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 9, Issue S02, 1 August 2003, Pages 850–851, https://doi.org/10.1017/S1431927603444255 Published: 24 July 2003 C2 - 2003/1/1/ C3 - Microscopy and Microanalysis DA - 2003/1/1/ DO - 10.1017/s1431927603444255 VL - 9 SP - 850-851 M1 - SUPPL. 2 UR - https://app.dimensions.ai/details/publication/pub.1113964956 ER - TY - JOUR TI - Nanostructures and deformation mechanisms in a cryogenically ball-milled Al-Mg alloy AU - Liao, X. Z. AU - Huang, J. Y. AU - Zhu, Y. T. AU - Zhou, F. AU - Lavernia, E. J. T2 - Philosophical Magazine AB - An Al-7.6 at.% Mg alloy was ball milled in liquid N2 for 8 h and its microstructures were investigated using transmission electron microscopy. Electron diffraction confirmed that the resulting powder is a supersaturated Al-Mg solid solution with an fcc structure. Three typical nanostructures with different grain-size ranges and shapes were observed and the deformation mechanisms in these structures were found to be different. High densities of dislocations were found in large crystallites, implying that dislocation slip is the dominant deformation mechanism. The dislocations rearranged to form small-angle subboundaries upon further deformation, resulting in the formation of medium-sized crystallites with diameters of 10-30 nm. In very small crystallites with dimensions less than 10 nm, twinning becomes an important deformation mechanism. The reasons for the different deformation mechanisms were discussed. Some defects, such as twin boundaries, and small- and large-angle grain boundaries were investigated in detail. DA - 2003/9// PY - 2003/9// DO - 10.1080/1478643031000152799 VL - 83 IS - 26 SP - 3065-3075 J2 - Philosophical Magazine LA - en OP - SN - 1478-6435 1478-6443 UR - http://dx.doi.org/10.1080/1478643031000152799 DB - Crossref ER - TY - JOUR TI - Grain boundary structure of nanocrystalline Cu processed by cryomilling AU - Huang, J. Y. AU - Liao, X. Z. AU - Zhu, Y. T. AU - Zhou, F. AU - Lavernia, E. J. T2 - Philosophical Magazine AB - The microstructures of cryogenically ball-milled Cu were investigated by high-resolution electron microscopy. It was found that the grain-size reduction is a dislocation-controlled continuous process which consists of the formation of small-angle grain boundaries (GBs), a gradual increase in misorientations as a result of accumulation of more dislocations and, finally, the formation of large-angle GBs. The GBs were generally curved, wavy or faceted, and heavily strained, which are typical characteristics of nanostructured materials. In addition, extrinsic dislocations were found in many GBs, indicating that most are in a high-energy non-equilibrium configuration, which is consistent with observations in equal-channel angular pressing processed Cu, Ni, and Al-Mg, repetitive corrugation and straightening processed Cu and room-temperature ball-milled Cu. These results support a still-disputed concept that GBs in nanostructured metals processed by severe plastic deformation are mostly in non-equilibrium states. DA - 2003/1// PY - 2003/1// DO - 10.1080/1478643031000083633 VL - 83 IS - 12 SP - 1407-1419 J2 - Philosophical Magazine LA - en OP - SN - 1478-6435 1478-6443 UR - http://dx.doi.org/10.1080/1478643031000083633 DB - Crossref ER - TY - JOUR TI - The molecular structure and intermolecular interactions of 1,3:2,4-dibenzylidene-D-sorbitol AU - Wilder, Elizabeth A. AU - Spontak, Richard J. AU - Hall, Carol K. T2 - Molecular Physics AB - The 1,3(R):2,4(S)-dibenzylidene-D-sorbitol (DBS) molecule is a low molar mass organic gelator (LMOG) that is capable of hydrogen-bonding with itself. As a consequence, DBS molecules self-organize into nanofibrillar networks at relatively low concentrations in a wide variety of organic solvents and polymers. In this work, molecular mechanics and molecular dynamics simulations were conducted to elucidate the equilibrium structure of DBS and the molecular interactions that govern DBS self-assembly. Molecular mechanics calculations performed on single DBS molecules with Cerius2 and InsightII software reveal that the phenyl rings tend to adopt an equatorial position and that the pendant hydroxyl group prefers to form an intramolecular hydrogen bond with an acetal oxygen, in contrast to the terminal hydroxyl group. Molecular mechanics and molecular dynamics on DBS dimers reveal that they are capable of forming hydrogen bonds and participating in π interactions, suggesting that the mechanism of nanofibrillar network formation may be complex, involving more than one type of physical interaction. DA - 2003/10/10/ PY - 2003/10/10/ DO - 10.1080/00268970310001597327 VL - 101 IS - 19 SP - 3017-3027 J2 - Molecular Physics LA - en OP - SN - 0026-8976 1362-3028 UR - http://dx.doi.org/10.1080/00268970310001597327 DB - Crossref ER - TY - CHAP TI - DNA-based Cryptography AU - Gehani, Ashish AU - LaBean, Thomas AU - Reif, John T2 - Aspects of Molecular Computing AB - Recent research has considered DNA as a medium for ultra-scale computation and for ultra-compact information storage. One potential key application is DNA-based, molecular cryptography systems. We present some procedures for DNA-based cryptography based on one-time-pads that are in principle unbreakable. Practical applications of cryptographic systems based on one-time-pads are limited in conventional electronic media by the size of the one-time-pad; however DNA provides a much more compact storage medium, and an extremely small amount of DNA suffices even for huge one-time-pads. We detail procedures for two DNA one-time-pad encryption schemes: (i) a substitution method using libraries of distinct pads, each of which defines a specific, randomly generated, pair-wise mapping; and (ii) an XOR scheme utilizing molecular computation and indexed, random key strings. These methods can be applied either for the encryption of natural DNA or for artificial DNA encoding binary data. In the latter case, we also present a novel use of chip-based DNA micro-array technology for 2D data input and output. Finally, we examine a class of DNA steganography systems, which secretly tag the input DNA and then hide it within collections of other DNA. We consider potential limitations of these steganographic techniques, proving that in theory the message hidden with such a method can be recovered by an adversary. We also discuss various modified DNA steganography methods which appear to have improved security. PY - 2003/// DO - 10.1007/978-3-540-24635-0_12 SP - 167-188 OP - PB - Springer Berlin Heidelberg SN - 9783540207818 9783540246350 UR - http://dx.doi.org/10.1007/978-3-540-24635-0_12 DB - Crossref ER - TY - JOUR TI - Big molecule ejection—SIMS vs. MALDI AU - Garrison, B.J. AU - Delcorte, A. AU - Zhigilei, L.V. AU - Itina, T.E. AU - Krantzman, K.D. AU - Yingling, Y.G. AU - McQuaw, C.M. AU - Smiley, E.J. AU - Winograd, N. T2 - Applied Surface Science AB - Using the results of molecular dynamics (MD) simulations, we discuss the question of whether the observed difference in mass limits in secondary ion mass spectrometry (SIMS) and matrix assisted laser desorption ionization (MALDI) are inherently related to the underlying physics of ejection or rather insufficient experimentation. The simulations show clearly that the physics of large molecule emission in SIMS and MALDI is very different. Consequently, we conclude that larger molecules can be ejected in MALDI than in SIMS. DA - 2003/1// PY - 2003/1// DO - 10.1016/S0169-4332(02)00661-X VL - 203-204 SP - 69-71 J2 - Applied Surface Science LA - en OP - SN - 0169-4332 UR - http://dx.doi.org/10.1016/s0169-4332(02)00661-x DB - Crossref KW - MALDI KW - organic SIMS KW - molecular dynamics KW - computer simulation ER - TY - JOUR TI - Photochemical ablation of organic solids AU - Yingling, Yaroslava G. AU - Garrison, Barbara J. T2 - Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms AB - We have investigated by molecular dynamics simulations the ablation of material that is onset by photochemical processes. We compare this system with only photochemical processes to a system containing photochemical and photothermal processes. The simulations reveal that ablation by purely photochemical processes is accompanied by the ejection of relatively cold massive molecular clusters from the surface of the sample. The top of the plume exhibits high temperatures whereas the residual part of the sample is cold. The removal of the damaged material through big molecular cluster ejection is consistent with experimental observations of low heat damage of material. DA - 2003/4// PY - 2003/4// DO - 10.1016/s0168-583x(02)01855-4 VL - 202 SP - 188-194 J2 - Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms LA - en OP - SN - 0168-583X UR - http://dx.doi.org/10.1016/s0168-583x(02)01855-4 DB - Crossref KW - molecular dynamics simulations KW - laser ablation KW - photochemical fragmentation KW - photochemical processes ER - TY - JOUR TI - Molecular dynamics simulations of matrix-assisted laser desorption - connections to experiment AU - Zhigilei, L.V. AU - Yingling, Y.G. AU - Itina, T.E. AU - Schoolcraft, T.A. AU - Garrison, B.J. T2 - International Journal of Mass Spectrometry AB - The molecular dynamics (MD) simulation technique has been applied to investigate fundamental aspects of matrix-assisted laser desorption. In this paper, we focus on direct comparisons of the results from the simulations with experimental data and on establishing links between the measured or calculated parameters and the basic mechanisms of molecular ejection. The results on the fluence dependence of the ablation/desorption yields and composition of the ejected plume are compared with mass spectrometry and trapping plate experiments. Implications of the prediction of a fluence threshold for ablation are discussed. The strongly forward-peaked velocity and angular distributions of matrix and analyte molecules, predicted in the simulations, are related to the experimental distributions. The shapes and amplitudes of the acoustic waves transmitted from the absorption region through the irradiated sample are compared to recent photoacoustic measurements and related to the ejection mechanisms. The conformational changes during plume evolution and the ejection velocities of analyte molecules are studied and the directions for future investigations are discussed. Finally, we demonstrate that the MD simulation technique can be used to model other processes relevant to mass spectrometry applications, such as laser disintegration of aerosol particles and laser ablation in the presence of photochemical reactions. DA - 2003/// PY - 2003/// DO - 10.1016/s1387-3806(02)00962-4 VL - 226 IS - 1 SP - 85-106 UR - https://publons.com/publon/3366925/ KW - ablation KW - MALDI KW - molecular dynamics ER - TY - JOUR TI - Computer Simulations of Laser Ablation of Molecular Substrates AU - Zhigilei, Leonid V. AU - Leveugle, Elodie AU - Garrison, Barbara J. AU - Yingling, Yaroslava G. AU - Zeifman, Michael I. T2 - Chemical Reviews AB - ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTComputer Simulations of Laser Ablation of Molecular SubstratesLeonid V. Zhigilei, Elodie Leveugle, Barbara J. Garrison, Yaroslava G. Yingling, and Michael I. ZeifmanView Author Information Department of Materials Science and Engineering, 116 Engineer's Way, University of Virginia, Charlottesville, Virginia 22904 Department of Chemistry, 152 Davey Laboratory, Penn State University, University Park, Pennsylvania 16802 Cite this: Chem. Rev. 2003, 103, 2, 321–348Publication Date (Web):January 15, 2003Publication History Received5 June 2002Published online15 January 2003Published inissue 1 February 2003https://doi.org/10.1021/cr010459rCopyright © 2003 American Chemical SocietyRequest reuse permissionsArticle Views2101Altmetric-Citations250LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (2 MB) Get e-AlertscloseSUBJECTS:Ablation,Cluster chemistry,Lasers,Materials,Molecules Get e-Alerts DA - 2003/2// PY - 2003/2// DO - 10.1021/cr010459r VL - 103 IS - 2 SP - 321-348 J2 - Chem. Rev. LA - en OP - SN - 0009-2665 1520-6890 UR - http://dx.doi.org/10.1021/cr010459r DB - Crossref ER - TY - JOUR TI - Computer Simulations of Laser Ablation of Molecular Substrates AU - Zhigilei, Leonid V. AU - Leveugle, Elodie AU - Garrison, Barbara J. AU - Yingling, Yaroslava G. AU - Zeifman, Michael I. T2 - ChemInform AB - Abstract For Abstract see ChemInform Abstract in Full Text. DA - 2003/5/6/ PY - 2003/5/6/ DO - 10.1002/chin.200318285 VL - 34 IS - 18 ER - TY - JOUR TI - The influence of structural defects on intra-granular critical currents of bulk MgB2 AU - SERQUIS, A AU - LIAO, XZ AU - CIVALE, L AU - al., T2 - IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY DA - 2003/// PY - 2003/// VL - 13 IS - 2 SP - 3068-3071 ER - TY - JOUR TI - Role of excess Mg and heat treatments on microstructure and critical current of MgB2 wires AU - SERQUIS, A AU - CIVALE, L AU - HAMMON, DL AU - al., T2 - JOURNAL OF APPLIED PHYSICS DA - 2003/// PY - 2003/// VL - 94 IS - 6 SP - 4024-4031 ER - TY - JOUR TI - Nanostructures in Ti processed by severe plastic deformation AU - ZHU, YT AU - HUANG, JY AU - GUBICZA, J AU - al., T2 - JOURNAL OF MATERIALS RESEARCH DA - 2003/// PY - 2003/// VL - 18 IS - 8 SP - 1908-1917 ER - TY - JOUR TI - Nanostructures and deformation mechanisms in a cryogenically ball-milled Al-Mg alloy AU - LIAO, XZ AU - HUANG, JY AU - ZHU, YT AU - al., T2 - PHILOSOPHICAL MAGAZINE DA - 2003/// PY - 2003/// VL - 83 IS - 26 SP - 3065-3075 ER - TY - JOUR TI - Microwave performance of high-density bulk MgB2 AU - FINDIKOGLU, AT AU - SERQUIS, A AU - CIVALE, L AU - al., T2 - APPLIED PHYSICS LETTERS DA - 2003/// PY - 2003/// VL - 83 IS - 1 SP - 108-110 ER - TY - JOUR TI - Microstructures and mechanical properties of ultrafine-grained Ti foil processed by equal-channel angular pressing and cold rolling AU - ZHU, YT AU - KOLOBOV, YR AU - GRABOVETSKAYA, GP AU - al., T2 - JOURNAL OF MATERIALS RESEARCH DA - 2003/// PY - 2003/// VL - 18 IS - 4 SP - 1011-1016 ER - TY - JOUR TI - Microstructure of cryogenic treated M2 tool steel AU - HUANG, JY AU - ZHU, YT AU - LIAO, XZ AU - al., T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING DA - 2003/// PY - 2003/// VL - 339 IS - 1-2 SP - 241-244 ER - TY - JOUR TI - Microstructure and high critical current of powder-in-tube MgB2 AU - SERQUIS, A AU - CIVALE, L AU - HAMMON, DL AU - al., T2 - APPLIED PHYSICS LETTERS DA - 2003/// PY - 2003/// VL - 82 IS - 11 SP - 1754-1756 ER - TY - JOUR TI - Microstructural evolution during recovery and recrystallization of a nanocrystalline Al-Mg alloy prepared by cryogenic ball milling AU - ZHOU, F AU - LIAO, XZ AU - ZHU, YT AU - al., T2 - ACTA MATERIALIA DA - 2003/// PY - 2003/// VL - 51 IS - 10 SP - 2777-2791 ER - TY - JOUR TI - Mg(B,O)(2) precipitation in MgB2 AU - LIAO, XZ AU - SERQUIS, A AU - ZHU, YT AU - al., T2 - JOURNAL OF APPLIED PHYSICS DA - 2003/// PY - 2003/// VL - 93 IS - 10 SP - 6208-6215 ER - TY - JOUR TI - Mechanical milling-induced deformation twinning in Fcc materials with high stacking fault energy AU - HE, JH AU - CHUNG, KH AU - LIAO, XZ AU - al., T2 - METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE DA - 2003/// PY - 2003/// VL - 34 IS - 3 SP - 707-712 ER - TY - JOUR TI - Issues on the design of bone-shaped short fiber composites AU - ZHU, YT AU - BEYERLEIN, IJ T2 - JOURNAL OF ADVANCED MATERIALS DA - 2003/// PY - 2003/// VL - 35 IS - 2 SP - 51-60 ER - TY - JOUR TI - Hot isostatic pressing of powder in tube MgB2 wires AU - SERQUIS, A AU - CIVALE, L AU - HAMMON, DL AU - al., T2 - APPLIED PHYSICS LETTERS DA - 2003/// PY - 2003/// VL - 82 IS - 17 SP - 2847-2849 ER - TY - JOUR TI - High critical currents in powder in tube MgB2 wires: Influence of microstructure and heat treatments AU - CIVALE, L AU - SERQUIS, A AU - HAMMON, DL AU - al., T2 - IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY DA - 2003/// PY - 2003/// VL - 13 IS - 2 SP - 3347-3350 ER - TY - JOUR TI - Grain refinement and properties of pure Ti processed by warm ECAP and cold rolling AU - STOLYAROV, , VV AU - ZHU, YT AU - ALEXANDROV, , IV AU - al., T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING DA - 2003/// PY - 2003/// VL - 343 IS - 1-2 SP - 43-50 ER - TY - JOUR TI - Grain boundary structure of nanocrystalline Cu processed by cryomilling AU - HUANG, JY AU - LIAO, XZ AU - ZHU, YT AU - al., T2 - PHILOSOPHICAL MAGAZINE DA - 2003/// PY - 2003/// VL - 83 IS - 12 SP - 1407-1419 ER - TY - JOUR TI - Effect of catalyst composition on carbon nanotube growth AU - LIAO, XZ AU - SERQUIS, A AU - JIA, QX AU - al., T2 - APPLIED PHYSICS LETTERS DA - 2003/// PY - 2003/// VL - 82 IS - 16 SP - 2694-2696 ER - TY - JOUR TI - Dislocation structure and crystallite size distribution in plastically deformed Ti determined by X-ray peak profile analysis AU - GUBICZA, J AU - DRAGOMIR, IC AU - RIBARIK, G AU - al., T2 - ZEITSCHRIFT FUR METALLKUNDE DA - 2003/// PY - 2003/// VL - 94 IS - 11 SP - 1185-1188 ER - TY - JOUR TI - Deformation twins in pure titanium processed by equal channel angular pressing AU - KIM, I AU - KIM, J AU - SHIN, DH AU - al., T2 - SCRIPTA MATERIALIA DA - 2003/// PY - 2003/// VL - 48 IS - 6 SP - 813-817 ER - TY - JOUR TI - Deformation twins in nanocrystalline Al AU - LIAO, XZ AU - ZHOU, F AU - LAVERNIA, EJ AU - al., T2 - APPLIED PHYSICS LETTERS DA - 2003/// PY - 2003/// VL - 83 IS - 24 SP - 5062-5064 ER - TY - JOUR TI - Deformation mechanism in nanocrystalline Al: Partial dislocation slip AU - LIAO, XZ AU - ZHOU, F AU - LAVERNIA, EJ AU - al., T2 - APPLIED PHYSICS LETTERS DA - 2003/// PY - 2003/// VL - 83 IS - 4 SP - 632-634 ER - TY - JOUR TI - Defect structures in MgB2 wires introduced by hot isostatic pressing AU - LIAO, XZ AU - SERQUIS, A AU - ZHU, YT AU - al., T2 - SUPERCONDUCTOR SCIENCE & TECHNOLOGY DA - 2003/// PY - 2003/// VL - 16 IS - 7 SP - 799-803 ER - TY - JOUR TI - Commercialization of nanostructured metals produced by severe plastic deformation processing AU - LOWE, TC AU - ZHU, YT T2 - ADVANCED ENGINEERING MATERIALS DA - 2003/// PY - 2003/// VL - 5 IS - 5 SP - 373-378 ER - TY - JOUR TI - Co-Mo catalyzed growth of multi-wall carbon nanotubes from CO decomposition AU - SERQUIS, A AU - LIAO, XZ AU - HUANG, JY AU - al., T2 - CARBON DA - 2003/// PY - 2003/// VL - 41 IS - 13 SP - 2635-2641 ER - TY - JOUR TI - Characterization of the microstructure of severely deformed titanium by X-ray diffraction profile analysis AU - GUBICZA, J AU - DRAGOMIR, LC AU - RIBARIK, G AU - al., T2 - MATERIALS SCIENCE, TESTING AND INFORMATICS DA - 2003/// PY - 2003/// VL - 414-4 SP - 229-234 ER - TY - JOUR TI - Vapor-liquid-solid growth of silicon-germanium nanowires AU - Lew, KK AU - Pan, L AU - Dickey, EC AU - Redwing, JM T2 - Advanced Materials DA - 2003/// PY - 2003/// DO - 10.1002/adma200306035 VL - 15 IS - 24 SP - 2073-+ UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000188051400008&KeyUID=WOS:000188051400008 ER - TY - JOUR TI - Raman spectroscopy and structure of crystalline gallium phosphide nanowires AU - Xiong, QH AU - Gupta, R AU - Adu, KW AU - Dickey, EC AU - Lian, GD AU - Tham, D AU - Fischer, JE AU - Eklund, PC T2 - Journal of Nanoscience and Nanotechnology AB - Gallium phosphide nanowires with a most probable diameter of approximately 20.0 nm and more than 10 microns in length have been synthesized by pulsed laser vaporization of a heated GaP/5% Au target. The morphology and microstructure of GaP nanowires have been investigated by scanning electron microscopy and transmission electron microscopy. Twins have been observed along the crystalline nanowires, which have a growth direction of [111]. Raman scattering shows a 4 cm-1 downshift of the longitudinal optical phonon peak in the nanowire with respect to the bulk; the transverse optical phonon frequency and line width are, however, the same as in the bulk. The quantum confinement model first proposed by Richter et al. cannot explain the observed behavior of the Raman modes. DA - 2003/// PY - 2003/// DO - 10.1166/jnn.2003.208 VL - 3 IS - 4 SP - 335-339 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000185818800010&KeyUID=WOS:000185818800010 KW - pulsed laser vaporization KW - gallium phosphide nanowires KW - Raman scattering ER - TY - JOUR TI - Modulated and ordered defect structures in electrically degraded Ni-BaTiO3 multilayer ceramic capacitors AU - Yang, GY AU - Dickey, EC AU - Randall, CA AU - Randall, MS AU - Mann, LA T2 - Journal of Applied Physics AB - Structural defects formed on {111} planes of BaTiO3 during the degradation of high performance multilayer Ni–BaTiO3 X7R ceramic capacitors are studied using transmission electron microscopy and electron energy loss spectroscopy (EELS). Regular pseudocubic barium titanate grains are present in as-produced (virginal) base-metal electrode capacitors. However, there is a coexistence of regular, modulated, and long-range ordered structures in intentionally electrically degraded devices. The EELS analysis demonstrates that the concentration of oxygen vacancies in barium titanate with modulated or ordered structures is higher than that in the regular perovskite grains. The clustering or accumulation of oxygen vacancies in the structural framework of BaTiO3 gives rise to the formation of new metastable structures. These observations are consistent with earlier models for degradation, but demonstrate that the details of the process may be more complex than originally assumed. Here we introduce new details on the nature of the reduction process and the manner in which the lattice accommodates the enhanced oxygen vacancy concentration towards the failed regions of the capacitors and in the vicinity of the “blocking” cathodic electrodes. DA - 2003/// PY - 2003/// DO - 10.1063/1.1615300 VL - 94 IS - 9 SP - 5990-5996 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000186138600081&KeyUID=WOS:000186138600081 ER - TY - JOUR TI - Low-temperature synthesis of large-area CNx nanotube arrays AU - Qian, DL AU - Andrews, R AU - Jacques, D AU - Kichambare, P AU - Lian, G AU - Dickey, EC T2 - Journal of Nanoscience and Nanotechnology AB - Well-aligned nitrogen-doped multiwall carbon nanotube arrays have been successfully grown over large areas on quartz and silicon wafers by floating-catalyst chemical vapor deposition at low temperatures (600 degrees C). These nitrogen-including nanotubes, derived from pyridine-ferrocene mixtures, have smaller outer diameters but larger inner diameters compared with carbon nanotubes grown from a xylene-ferrocene mixture under similar conditions. The N-doped nanotubes exhibit bamboo-like structures in the core. Elemental analysis and electron energy loss spectroscopy analysis show that the as-prepared nanotubes contain as much as 2.62 wt.% N, with most of the N concentrated in the inner few shells of the nanotube. Such large-scale arrays of well-aligned N-doped nanotubes on silicon wafers have a current density as high as 23.8 mA/cm2 at an applied electric field of 17 V/micron, which can be further improved by patterning the tubes and coating the silicon substrate with a conductive thin metal film for the fabrication of flat panel displays. DA - 2003/// PY - 2003/// DO - 10.1166/jnn.2003.159 VL - 3 IS - 1-2 SP - 93-97 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000183793100010&KeyUID=WOS:000183793100010 KW - nanotubes KW - pyrolysis KW - doping KW - alignment KW - characterizations KW - field emission ER - TY - JOUR TI - Interface structure and chemistry in ZnSe/Ga1-xMnxAs/ZnSe heterostructures AU - Lian, GD AU - Dickey, EC AU - Chun, SH AU - Ku, KC AU - Samarth, N T2 - Applied Physics Letters AB - The structure and chemical composition of ZnSe/Ga1−xMnxAs/ZnSe multilayers grown on (100) GaAs substrates are investigated by high-resolution transmission electron microscopy imaging and spectroscopy techniques. While all layers grow epitaxially and the Ga1−xMnxAs layer is free of planar defects, a high density of stacking faults is observed in the ZnSe layer over Ga1−xMnxAs. The composition of the ferromagnetic layer is measured to be Ga0.93Mn0.07As, and the Mn valence was determined to be 2+. Compositional profiles across the interfaces quantified by electron energy-loss spectroscopy show that the ZnSe/Ga1−xMnxAs interfaces are wider than the ZnSe/GaAs–substrate interface, which is mainly attributed to interfacial roughness. DA - 2003/// PY - 2003/// DO - 10.1063/1.1577825 VL - 82 IS - 21 SP - 3656-3658 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000182993700024&KeyUID=WOS:000182993700024 ER - TY - JOUR TI - Individual single-walled nanotubes and hydrogels made by oxidative exfoliation of carbon nanotube ropes AU - Kovtyukhova, NI AU - Mallouk, TE AU - Pan, L AU - Dickey, EC T2 - Journal of the American Chemical Society AB - Single-walled carbon nanotubes were oxidized by a technique previously developed for the oxidation of graphite to graphite oxide (GO). This process involves treatment with concentrated H2SO4 containing (NH4)2S2O8 and P2O5, followed by H2SO4 and KMnO4. Oxidation results in complete exfoliation of nanotube ropes to yield individual oxidized tubes that are 40−500 nm long. The C:O:H atomic ratio of vacuum-dried oxidized nanotubes is approximately 2.7:1.0:1.2. XPS and IR spectra show evidence for surface O−H, CO, and COOH groups. The oxidized nanotubes slowly form viscous hydrogels at unusually low concentration (≥0.3 wt %), and this behavior is attributed to the formation of a hydrogen-bonded nanotube network. The oxidized tubes bind readily to amine-coated surfaces, on which they adsorb as smooth and dense monolayer films. Thin films of the oxidized nanotubes show ohmic current−voltage behavior, with resistivities in the range of 0.2−0.5 Ω-cm. DA - 2003/// PY - 2003/// DO - 10.1021/ja0344516 VL - 125 IS - 32 SP - 9761-9769 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000184654700051&KeyUID=WOS:000184654700051 ER - TY - CHAP TI - Grain boundary segregation in titanium dioxide: Evaluation of relative driving forces for segregation AU - Wang, QL AU - Lian, GD AU - Dickey, EC T2 - Structure-Property Relationships of Oxide Surfaces and Interfaces Ii PY - 2003/// VL - 751 SP - 179-190 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000183444800030&KeyUID=WOS:000183444800030 ER - TY - JOUR TI - Extreme changes in the electrical resistance of titania nanotubes with hydrogen exposure AU - Varghese, OK AU - Gong, DW AU - Paulose, M AU - Ong, KG AU - Dickey, EC AU - Grimes, CA T2 - Advanced Materials AB - Extremely sensitive, drift‐free, and robust hydrogen sensors based on titania nanotube arrays (see Figure) are reported. Very large changes in the electrical conductivity of the nanotubes upon exposure to hydrogen gas have been measured, over one order of magnitude greater than the previous record. Dependence of the electrical conductivity on both temperature and nanotube pore size is found. DA - 2003/// PY - 2003/// DO - 10.1002/adma.200304586 VL - 15 IS - 7-8 SP - 624-627 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000182552300021&KeyUID=WOS:000182552300021 ER - TY - JOUR TI - Crystallization and high-temperature structural stability of titanium oxide nanotube arrays AU - Varghese, OK AU - Gong, DW AU - Paulose, M AU - Grimes, CA AU - Dickey, EC T2 - Journal of Materials Research DA - 2003/// PY - 2003/// DO - 10.1557/JMR.2003.0022 VL - 18 IS - 1 SP - 156-165 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000180363400022&KeyUID=WOS:000180363400022 ER - TY - JOUR TI - Ceramic/metal interface structures and their relationship to atomic- and meso-scale properties AU - Sinnott, SB AU - Dickey, EC T2 - Materials Science & Engineering R-Reports AB - Ceramic/metal interfaces have vast technological significance and are used in a variety of applications. This has prompted a concerted effort to develop fundamental structure/property relationships for these structures. This article critically reviews recent advances in complementary experimental and theoretical studies of ceramic/metal interfaces to provide an overview of progress made towards developing these relationships. In particular, the focus is on the structure, characterization, and modeling of non-reactive, bulk ceramic/metal interfaces. This includes determining interface atomic structure and chemistry and investigating impurity segregation to the interfaces. Additionally, the most important advances in the experimental and theoretical modeling of interfacial structure and chemistry are reviewed and comments are provided on the future outlook of this field. DA - 2003/// PY - 2003/// DO - 10.1016/j.mser.2003.09.001 VL - 43 IS - 1-2 SP - 1-59 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000188003000001&KeyUID=WOS:000188003000001 KW - metal KW - ceramic KW - interface KW - segregation KW - transmission electron microscopy KW - atom probe field ion microscopy KW - modeling ER - TY - JOUR TI - A sentinel sensor network for hydrogen sensing AU - Grimes, CA AU - Ong, KG AU - Varghese, OK AU - Yang, XP AU - Mor, G AU - Paulose, M AU - Dickey, EC AU - Ruan, CM AU - Pishko, MV AU - Kendig, JW AU - Mason, AJ T2 - Sensors AB - A wireless sensor network is presented for in-situ monitoring of atmospheric hydrogen concentration. The hydrogen sensor network consists of multiple sensor nodes, equipped with titania nanotube hydrogen sensors, distributed throughout the area of interest; each node is both sensor, and data-relay station that enables extended wide area monitoring without a consequent increase of node power and thus node size. The hydrogen sensor is fabricated from a sheet of highly ordered titania nanotubes, made by anodization of a titanium thick film, to which platinum electrodes are connected. The electrical resistance of the hydrogen sensor varies from 245 Ω at 500 ppm hydrogen, to 10.23 kΩ at 0 ppm hydrogen (pure nitrogen environment). The measured resistance is converted to voltage, 0.049 V at 500 ppm to 2.046 V at 0 ppm, by interface circuitry. The microcontroller of the sensor node digitizes the voltage and transmits the digital information, using intermediate nodes as relays, to a host node that downloads measurement data to a computer for display. This paper describes the design and operation of the sensor network, the titania nanotube hydrogen sensors with an apparent low level resolution of approximately 0.05 ppm, and their integration in one widely useful device. DA - 2003/// PY - 2003/// DO - 10.3390/s30300069 VL - 3 IS - 3 SP - 69-82 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000182273100003&KeyUID=WOS:000182273100003 KW - sensor network KW - sensor node KW - sensor array KW - hydrogen KW - sensor KW - nanotube ER - TY - CONF TI - Population dynamics of nitrifying bacteria in intermittently-aerated reactors treating high nitrogen wastewater AU - Mota, C. R. AU - Hu, Z. AU - Cheng, J. AU - Reyes F. L., C2 - 2003/// C3 - WEFTEC.03 : Conference Program & Exhibitor Guide : 76th Annual Technial Exhibition and Conference : the water quality event : Los Angeles, October 11-15, 2003, Los Angeles Convention Center DA - 2003/// ER - TY - CONF TI - Detection of unusually high levels of nitrifying bacteria in reactors treating high nitrogen wastewater AU - Mota, C. R. AU - Hu, Z. AU - Cheng, J. AU - Reyes F. L., C2 - 2003/// C3 - American Society for Microbiology 103rd General Meeting, May 18-22, 2003, Washington, D.C DA - 2003/// SN - 1555812732 ER - TY - PAT TI - Solventless, resistless direct dielectric patterning AU - Gleason, K. K. AU - Ober, C. AU - Herr, D. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Ultrananocrystalline diamond cantilever wide dynamic range acceleration/vibration/pressure sensor AU - Krauss, A. R. AU - Gruen, D. M. AU - Pellin, M. J. AU - Auciello, O. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Gallium nitride materials and methods AU - Weeks, T. W. AU - Piner, E. L. AU - Gehrke, T. AU - Linthicum, K. J. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Gallium nitride material devices and methods including backside vias AU - Weeks, T. W. AU - Piner, E. L. AU - Borges, R. M. AU - Linthicum, K. J. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Multi-layer conductor-dielectric oxide structure AU - Maria, J.-P AU - Kingon, A. AU - Dunn, G. AU - Streiffer, S.Cheek AU - K., Zhang AU - M.-X., AU - Savic, J. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Broadband spectroscopic rotating compensator ellipsometer AU - Aspnes, D. E. AU - Opsal, J. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - System and method for inhibiting imprinting of capacitor structures of a memory AU - Basceri, C. AU - Gealy, D. F. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Plasma enhanced chemical vapor deposition method of forming titanium silicide comprising layers AU - Basceri, C. AU - Vasilyeva, I. AU - Derraa, A. AU - Campbell, P. H. AU - Sandhu, G. S. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Physical vapor deposition methods AU - Basceri, C. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Methods of depositing a layer comprising tungsten and methods of forming a transistor gate line AU - Basceri, C. AU - Derderian, G. J. AU - Visokay, M. R. AU - Drynan, J. M. AU - Sandhu, G. S. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Methods for forming conductive structures and structures regarding same AU - Basceri, C. AU - Sandhu, G. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Methods for forming and integrated circuit structures containing ruthenium and tungsten containing layers AU - Agarwal, V. K. AU - Derderian, G. AU - Sandhu, G. S. AU - Li, W. M. AU - Visokay, M. AU - Basceri, C. AU - Yang, S. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Method of forming haze- free BST films AU - Basceri, C. AU - Sandhu, G. S. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Method of forming a non-conformal layer over and exposing a trench AU - Chopra, D. AU - Donohoe, K. G. AU - Basceri, C. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Method of forming DRAM circuitry AU - Basceri, C. AU - Derderian, G. J. AU - Visokay, M. R. AU - Drynan, J. M. AU - Sandhu, G. S. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Method of etching a substantially amorphous TA2O5 comprising layer AU - Basceri, C. AU - Derderian, G. J. AU - Visokay, M. R. AU - Drynan, J. M. AU - Sandhu, G. S. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Method for controlling deposition of dielectric films AU - Basceri, C. AU - Gealy, D. AU - Sandhu, G. S. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Dielectric films and capacitor structures including same AU - Basceri, C. AU - Gealy, D. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Dielectric cure for reducing oxygen vacancies AU - Basceri, C. AU - Sandhu, G. S. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - DRAM processing methods AU - Basceri, C. AU - Sandhu, G. S. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Capacitor with high dielectric constant materials AU - Basceri, C. AU - Sandhu, G. S. AU - Yang, S. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - JOUR TI - Simplified bond-hyperpolarizability model of second- and fourth-harmonic generation: application to Si-SiO2 interfaces AU - Aspnes, DE AU - Hansen, JK AU - Peng, HJ AU - Powell, GD AU - Wang, JFT T2 - PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS AB - Abstract We recently developed a simplified bond‐hyperpolarizability model (SBHM) to describe the variation of second‐ and fourth‐harmonic‐generation (SHG, FHG) intensities as a function of sample azimuth angle, and applied it to various Si‐dielectric interfaces. The approach provides an efficient representation of these data with fewer parameters than required by Fourier or tensorial representations. In addition, these parameters have a direct physical meaning in microscopic terms. The model is simple enough to allow analytic expressions to be obtained for SHG and FHG intensities for (001) and (111) interfaces. SHG absorption is shown to result in easily recognized features in anisotropy data. Relative amplitudes of FHG intensities of the (001)Si–SiO 2 interface among the three nonvanishing polarization combinations are shown to be consistent to a factor of about 2. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2003/12// PY - 2003/12// DO - 10.1002/pssb.200303825 VL - 240 IS - 3 SP - 509-517 SN - 1521-3951 ER - TY - JOUR TI - Physical organogels composed of amphiphilic block copolymers and 1,3 : 2,4-dibenzylidene-D-sorbitol AU - Wilder, EA AU - Hall, CK AU - Spontak, RJ T2 - JOURNAL OF COLLOID AND INTERFACE SCIENCE AB - The 1,3:2,4-dibenzylidene-D-sorbitol (DBS) molecule is capable of self-organizing into nanoscale fibrils through intermolecular forces such as hydrogen bonding and π interactions. At sufficiently high concentrations (typically less than ∼2 wt%), the nanofibrils can form a network that promotes physical gelation of the matrix medium. Previous studies have investigated the mechanism of DBS-induced gelation and the features of DBS-containing gels in poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG). In this work, we examine the effect of adding DBS to a series of amphiphilic PPG-b-PEG-b-PPG triblock copolymers differing in composition and molecular weight. Dynamic rheological measurements reveal that the resultant gels are thermoreversible (i.e., they exhibit comparable mechanical properties before dissolution and after reformation under quiescent conditions), exhibiting a maximum in the elastic modulus (G′) at temperatures near the gel dissolution (Td) and formation (Tf) temperatures. Both Td and Tf tend to increase with increasing DBS concentration and PPG content, and their difference decreases with increasing PPG fraction in the copolymer. The magnitude of G′ is sensitive to copolymer composition and polymer identity at low DBS concentrations, but becomes polymer-independent as the DBS network saturates at concentrations in excess of ∼1 wt%. DA - 2003/11/15/ PY - 2003/11/15/ DO - 10.1016/S0021-9797(03)00619-2 VL - 267 IS - 2 SP - 509-518 SN - 0021-9797 ER - TY - JOUR TI - Wavelength-dependent Raman scattering of hydrogenated amorphous silicon carbon with red, green, and blue light excitation AU - Park, M AU - Sakhrani, V AU - Maria, JP AU - Cuomo, JJ AU - Teng, CW AU - Muth, JF AU - Ware, ME AU - Rodriguez, BJ AU - Nemanich, RJ T2 - JOURNAL OF MATERIALS RESEARCH AB - This study presents results of wavelength-dependent Raman scattering from amorphous silicon carbon (a-Si:C:H). The a-Si:C:H films were produced by radio-frequency plasma-enhanced chemical vapor deposition. Prior results with amorphous carbon indicate that laser excitation selectively probes clusters with differing sizes. Our measurements with a-Si:C:H indicate that when using red (632.8 nm), green (514.5 nm), and blue (488.0 nm) excitation, the Raman D and G peaks shift to higher wave numbers as the excitation energy increases. The higher frequency is associated with smaller clusters that are preferentially excited with higher photon energy. It appears that photoluminescence occurs due to radiative recombination from intracluster transitions in Si-alloyed sp 2 -bonded carbon clusters DA - 2003/4// PY - 2003/4// DO - 10.1557/JMR.2003.0106 VL - 18 IS - 4 SP - 768-771 SN - 2044-5326 ER - TY - JOUR TI - The molecular structure and intermolecular interactions of 1,3: 2,4-dibenzylidene-D-sorbitol AU - Wilder, E. A. AU - Spontak, Richard AU - Hall, C. K. T2 - Molecular Physics DA - 2003/// PY - 2003/// DO - 10.1080/0268970310001597327 VL - 101 IS - 19 SP - 3017–3027 ER - TY - JOUR TI - Rectifying electrical characteristics of La0.7Sr0.3MnO3/ZnO heterostructure AU - Tiwari, A AU - Jin, C AU - Kumar, D AU - Narayan, J T2 - APPLIED PHYSICS LETTERS AB - We have fabricated a p–n junction, consisting of p-type manganite (La0.7Sr0.3MnO3) and n-type ZnO layers grown on sapphire substrate. This junction exhibits excellent rectifying behavior over the temperature range 20–300 K. Electrical characteristics of La0.7Sr0.3MnO3 (LSMO) film in this heterostructure are found to be strongly modified by the built-in electric field at the junction. It has been shown that by applying the external bias voltage, the thickness of the depletion layer, and hence, the electrical and magnetic characteristics of LSMO film can precisely be modified. DA - 2003/9/1/ PY - 2003/9/1/ DO - 10.1063/1.1605801 VL - 83 IS - 9 SP - 1773-1775 SN - 0003-6951 ER - TY - JOUR TI - Piezoelectric resonating structures for microelectronic cooling AU - Wu, T. AU - Ro, P. I. AU - Kingon, A. I. AU - Mulling, J. F. T2 - Smart Materials & Structures AB - The design of piezoelectric resonating structures was investigated for generating acoustic streaming which may be used for cooling microelectronic components. The vibration characteristics of different piezoelectric structures were simulated by the finite element method and validated with analytical approaches. Considering the product of resonance frequency and dynamic tip deflection as a performance merit, the effects of length and location of the actuators as well as the boundary conditions were analyzed for four different piezoelectric resonator designs. Results show that there exist optimal length and location of actuators on the passive structures. DA - 2003/// PY - 2003/// DO - 10.1088/0964-1726/12/2/304 VL - 12 IS - 2 SP - 181-187 ER - TY - JOUR TI - Optical and structural studies of hydride vapor phase epitaxy grown GaN AU - Chang, YC AU - Cai, AL AU - Muth, JF AU - Kolbas, RM AU - Park, M AU - Cuomo, JJ AU - Hanser, A AU - Bumgarner, J T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Thick films of hydride vapor phase epitaxy (HVPE) grown GaN were studied by various techniques. Time-integrated and time-resolved photoluminescence (PL) measurements were performed at room temperature and 77 K. The time-integrated PL spectrum has no observed deep-level transitions and a very narrow linewidth, which indicates good material quality. Time-resolved PL spectra are also presented and the temporal evolution of the PL around the band-gap exhibits a biexponential decay with a fast and a slow decay component. Cathodoluminescence, x-ray, and Raman spectroscopy were also used. The full width half maximum of the x-ray rocking curve for our sample is approximately 375 arcsec. The polarized Raman spectra exhibited only the allowed modes. The deposited GaN films were found to be relatively stress free. The x ray and Raman analysis also revealed that the HVPE-grown GaN films are of high crystal quality. The effect of thermal annealing on the sample was also investigated by time-integrated and time-resolved PL and Raman spectroscopy. No significant changes in the material were observed in either time-integrated or Raman spectroscopy. The film was thermally stable upon annealing up to 1000 °C in N2 ambient based on the results of these measurements. In time-resolve photoluminescence measurement, the temporal evolution of the band-edge transitions broadens after each annealing step and is significantly different after the 1000 °C anneal. DA - 2003/// PY - 2003/// DO - 10.1116/1.1568346 VL - 21 IS - 3 SP - 701-705 SN - 0734-2101 ER - TY - JOUR TI - Measurement of the band offsets of SiO2 on clean n- and p-type GaN(0001) AU - Cook, TE AU - Fulton, CC AU - Mecouch, WJ AU - Tracy, KM AU - Davis, RF AU - Hurt, EH AU - Lucovsky, G AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - The band alignment at the SiO2-GaN interface is important for passivation of high voltage devices and for gate insulator applications. X-ray photoelectron spectroscopy and ultraviolet photoemission spectroscopy have been used to observe the interface electronic states as SiO2 was deposited on clean GaN(0001) surfaces. The substrates, grown by metallorganic chemical vapor deposition, were n- (1×1017) and p-type (2×1018) GaN on 6H-SiC(0001) with an AlN(0001) buffer layer. The GaN surfaces were atomically cleaned via an 860 °C anneal in an NH3 atmosphere. For the clean surfaces, n-type GaN showed upward band bending of 0.3±0.1 eV, while p-type GaN showed downward band bending of 1.3±0.1 eV. The electron affinity for n- and p-type GaN was measured to be 2.9±0.1 and 3.2±0.1 eV, respectively. To avoid oxidizing the GaN, layers of Si were deposited on the clean GaN surface via ultrahigh vacuum e-beam deposition, and the Si was oxidized at 300 °C by a remote O2 plasma. The substrates were annealed at 650 °C for densification of the SiO2 films. Surface analysis techniques were performed after each step in the process, and yielded a valence band offset of 2.0±0.2 eV and a conduction band offset of 3.6±0.2 eV for the GaN-SiO2 interface for both p- and n-type samples. Interface dipoles of 1.8 and 1.5 eV were deduced for the GaN-SiO2 interface for the n- and p-type surfaces, respectively. DA - 2003/4/1/ PY - 2003/4/1/ DO - 10.1063/1.1559424 VL - 93 IS - 7 SP - 3995-4004 SN - 0021-8979 ER - TY - JOUR TI - Influence of strain, surface diffusion and Ostwald ripening on the evolution of nanostructures for erbium on Si(001) AU - Fitting, L AU - Zeman, MC AU - Yang, WC AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - This study explores the evolution of nanoscale islands and wire structures during deposition and surface ripening. Ultraviolet photoelectron emission microscopy has been employed to study the real time growth process of individual erbium silicide nanostructures on Si(001) surfaces at temperatures up to 1050 °C. During the initial island formation process compact islands form and some undergo a shape transition to elongated islands oriented along the 〈110〉 directions of the Si substrate. The initial island formation is driven by the surface and interface energies of the silicide/Si structure. The widths of the growing islands remain essentially constant while the lengths increase. The observed elongated islands are ∼150 nm wide, which is larger than the width of prior reported erbium silicide nanowire structures. We propose that the ∼150 nm elongated islands are partially relaxed, possibly through the formation of misfit dislocations. The results indicate a temperature regime where island growth is mainly governed by surface diffusion of the deposited Er adatoms and a higher temperature regime where Ostwald ripening contributes to the island morphology. DA - 2003/4/1/ PY - 2003/4/1/ DO - 10.1063/1.1557787 VL - 93 IS - 7 SP - 4180-4184 SN - 1089-7550 ER - TY - JOUR TI - Highly CO2-permeable and selective polymer nanocomposite membranes AU - Patel, NP AU - Miller, AC AU - Spontak, RJ T2 - ADVANCED MATERIALS AB - As technologies turn to more efficient routes to remove CO 2 from mixed gas streams for H 2 or air purification, new cost‐effective multifunctional materials are needed for the separation processes. Here, hybrid poly(ethylene glycol)/fumed silica nanocomposite membranes exhibiting high CO 2 /H 2 selectivity (> 11) and CO 2 permeability (∼ 83 Barrer), as well as robust mechanical properties and optical clarity, are reported (see Figure). DA - 2003/5/2/ PY - 2003/5/2/ DO - 10.1002/adma.200304712 VL - 15 IS - 9 SP - 729-733 SN - 0935-9648 ER - TY - JOUR TI - Gel network development inn AB, ABA, and AB/ABA block copolymer solutions inn a selective solvent AU - Wilder, E. A. AU - White, S. A. AU - Smith, S. D. AU - Spontak, Richard T2 - Polymer gels: Fundamentals and applications AB - In the presence of a selective solvent, ordered block copolymers form micelles that, at sufficiently high copolymer concentrations, serve to stabilize a three-dimensional network and promote physical gelation. This study examines the steady and dynamic rheological properties of micellar solutions composed of AB diblock, ABA triblock and bidisperse mixtures of AB and ABA copolymer molecules. Of particular interest is the unexpected improvement in network development upon addition of an AB copolymer to an ABA copolymer at constant solution composition. This behavior is observed for ABA/solvent systems above and below the critical gelation concentration, and is interpreted in terms of the volume exclusion that occurs in bidisperse mixture of grafted chains. CN - QD549.2.P64 P653 2003 DA - 2003/// PY - 2003/// DO - 10.1021/bk-2002-0833.ch017 VL - 833 SP - 248–261 ER - TY - JOUR TI - Effect of an electric field on microstructure coarsening in 60Sn40Pb solder joints AU - Jung, K AU - Conrad, H T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - The influence of an electrostatic field E=15 and 25 kV cm−1 on the microstructure coarsening in 60Sn40Pb solder joints annealed at 150 °C was determined. Without a field the following were found: (a) the eutectic Pb and Sn phase size distributions (PSDs) fit the Bitti–DiNunzio model, (b) the phase size coarsening time exponent m=0.25 and (c) the intermetallic compound (IC) growth time exponent p=0.33. The field had only a slight effect on the PSDs and on the time exponents m or p; it, however, retarded significantly the rates of phase coarsening and of IC growth. The mechanism by which the field produced the retarding effects is not clear. A likely possibility is that it reduced the governing diffusion coefficient. DA - 2003/9/15/ PY - 2003/9/15/ DO - 10.1016/s0921-5093(02)00851-1 VL - 356 IS - 1-2 SP - 8-16 SN - 1873-4936 KW - electric field KW - microstructure coarsening KW - phase size distribution KW - kinetics ER - TY - JOUR TI - Bias frequency, waveform and duty-cycle effects on the bias-enhanced nucleation of epitaxial diamond AU - Wolter, SD AU - Okuzumi, F AU - Prater, JT AU - Sitar, Z T2 - THIN SOLID FILMS AB - In contrast to conventional DC bias-enhanced nucleation, a pre-carburization step was not needed in the processing of epitaxial diamond on (1 0 0) silicon using pulsed biasing. Otherwise, the procedure showed little frequency dependence on the epitaxial process in the range of 1 Hz–2 kHz, resulting in a constant percentage of highly oriented diamond of nearly 50%. The only variation with frequency was a linear increase in the bias current and a corresponding decrease in the biasing time required to form a quasi-continuous nucleation layer. In contrast, the variation of a 60-Hz square waveform duty cycle from 3 to 75% showed a decreasing hyperbolic relationship with the percentage of oriented diamond, with a plateau of ∼45% occurring at duty cycles of ⩽17%. The bias time to film formation was also determined to be inversely proportional to the duty cycle. The collective data highlights the relevance of the waveform attributes on the epitaxial nucleation of diamond on (1 0 0) silicon. DA - 2003/9/1/ PY - 2003/9/1/ DO - 10.1016/S0040-6090(03)00827-7 VL - 440 IS - 1-2 SP - 145-151 SN - 0040-6090 KW - chemical vapor deposition KW - diamond KW - epitaxy KW - plasma processing and deposition ER - TY - JOUR TI - Application of scanning transmission X-ray microscopy to the rubber industry AU - Winesett, DA AU - Ade, H AU - Smith, AP AU - Urquhart, SG AU - Dias, AJ AU - Stevens, P T2 - RUBBER CHEMISTRY AND TECHNOLOGY AB - Abstract Materials of commercial significance in the rubber industry are usually multi-component systems composed of several elastomers and various fillers. Elucidating the complex morphology that can arise from blending and understanding how this affects the various properties are essential. A technique advantageous to the study of multi-component elastomeric systems is Scanning Transmission X-ray Microscopy (STXM). STXM utilizes the chemical sensitivity of Near Edge X-ray Absorption Fine Structure (NEXAFS) and combines with relatively high spatial resolution and low beam damage to allow the successful characterization of multi-component materials that may be difficult or impossible with other techniques. An overview of the technique and example applications for the rubber industry is presented. DA - 2003/// PY - 2003/// DO - 10.5254/1.3547773 VL - 76 IS - 4 SP - 803-811 SN - 1943-4804 ER - TY - JOUR TI - A new approach for calculating the electronic structure and vibrational properties of non-crystalline solids: Effective charges for infrared-active normal mode vibrations in oxide and chalcogenide materials AU - Lucovsky, G. AU - Sremaniak, L. S. AU - Mowrer, T. AU - Whitten, J. L. T2 - Journal of Non-crystalline Solids DA - 2003/// PY - 2003/// VL - 326 IS - 2003 Oct 1 SP - 14- ER - TY - JOUR TI - Would diamond nanorods be stronger than fullerene nanotubes? AU - Shenderova, O AU - Brenner, D AU - Ruoff, RS T2 - NANO LETTERS AB - On the basis of literature ab initio data, we show that diamond nanorods would have a brittle fracture force and a zero strain stiffness that exceeds carbon nanotubes for radii greater than about 1−3 nm, depending on the orientation of the diamond nanorod. The energetic stability of diamond nanorods is predicted by molecular modeling to be comparable to single-walled carbon nanotubes. It is concluded that diamond nanorods represent an important and viable target structure for synthesis. DA - 2003/6// PY - 2003/6// DO - 10.1021/nl025949t VL - 3 IS - 6 SP - 805-809 SN - 1530-6992 ER - TY - JOUR TI - Surface morphology and strain of GaN layers grown using 6H-SiC(0001) substrates with different buffer layers AU - Einfeldt, S AU - Reitmeier, ZJ AU - Davis, RF T2 - JOURNAL OF CRYSTAL GROWTH AB - The evolution of both the surface morphology and the strain in GaN layers grown by metalorganic vapor phase epitaxy on either AlN or AlxGa1−xN (x≈0.15) buffer layers previously deposited on 6H-SiC(0 0 0 1) substrates has been investigated by varying the layer thickness from one GaN bilayer to 4μm. The GaN surfaces initially contained pits and undulations; the latter became smoother with continued growth. The growth of a 1–1.5 nm thick and continuous wetting layer and the subsequent formation of islands within the undulations are characteristic of the Stranski–Krastanov growth mode observed for the growth of GaN on AlN. The islands coalesced within the first 10 nm. Instead, a step-flow growth mode was observed for the growth of GaN on AlGaN. Increasing the thickness of the GaN grown on either AlN or AlGaN caused these biaxially stressed layers to gradually change their state of stress from compression to tension with regard to both their average strain and their local strain along the growth direction. The compressive and tensile stress components are attributed to the mismatch in lattice parameters between the GaN and the buffer layer and the mismatch in the coefficients of thermal expansion between GaN and SiC, respectively. A portion of the compressive stress is relieved within the first 20 nm of GaN grown on AlN buffer layer. The relief of the remaining stress follows an exponential dependence on the thickness of the GaN layer with values for the characteristic decay length of 0.24 and 0.64μm for the AlN and AlGaN buffer layer, respectively. The relaxation mechanism is discussed in terms of the formation of misfit dislocations via surface undulations. DA - 2003/6// PY - 2003/6// DO - 10.1016/S0022-0248(03)01039-X VL - 253 IS - 1-4 SP - 129-141 SN - 0022-0248 KW - stresses KW - surface structure KW - metalorganic vapor phase epitaxy KW - nitrides ER - TY - PAT TI - Supermolecular structures and devices made from same AU - Herr, D. J. C. AU - Zhirnov, V. V. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - JOUR TI - Spectroscopic study of chemical phase separation in zirconium silicate alloys AU - Rayner, G. B. AU - Kang, D. AU - Lucovsky, G. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 2003/// PY - 2003/// VL - 21 IS - 4 SP - 1783-1791 ER - TY - JOUR TI - Soft x-ray photoelectron spectroscopy of (HfO2)(x)(SiO2)(1-x) high-k gate-dielectric structures AU - Ulrich, M. D. AU - Hong, J. G. AU - Rowe, J. E. AU - Lucovsky, G. AU - Chan, A. S. Y. AU - Madey, T. E. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 2003/// PY - 2003/// VL - 21 IS - 4 SP - 1777-1782 ER - TY - JOUR TI - Phase behavior of poly(methyl methacrylate)/poly(vinylidene fluoride) blends with and without high-pressure CO2 AU - Walker, TA AU - Melnichenko, YB AU - Wignall, GD AU - Spontak, RJ T2 - MACROMOLECULES AB - ADVERTISEMENT RETURN TO ISSUECommunication to the...Communication to the EditorNEXTPhase Behavior of Poly(methyl methacrylate)/Poly(vinylidene fluoride) Blends with and without High-Pressure CO2Teri A. Walker, Yuri B. Melnichenko, George D. Wignall, and Richard J. SpontakView Author Information Departments of Chemical Engineering and Materials Science & Engineering, North Carolina State University, Raleigh, North Carolina 27695, and Condensed Matter Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 Cite this: Macromolecules 2003, 36, 12, 4245–4249Publication Date (Web):May 23, 2003Publication History Received11 February 2003Published online23 May 2003Published inissue 1 June 2003https://doi.org/10.1021/ma030103cCopyright © 2003 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views347Altmetric-Citations12LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. 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Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (86 KB) Get e-AlertsSUBJECTS:Differential scanning calorimetry,Fluoropolymers,Organic compounds,Polymers,Scattering Get e-Alerts DA - 2003/6/17/ PY - 2003/6/17/ DO - 10.1021/ma030103c VL - 36 IS - 12 SP - 4245-4249 SN - 0024-9297 ER - TY - PAT TI - Pendeoepitaxial methods of fabricating gallium nitride semiconductor layers on sapphire substrates, and gallium nitride semiconductor structures fabricated thereby AU - Gehrke, T. AU - Linthicum, K. J. AU - Davis, R. F. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Pendeoepitaxial methods of fabricating gallium nitride semiconductor layers on sapphire substrates AU - Gehrke, T. AU - Linthicum, K. J. AU - Davis, R. F. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - JOUR TI - Micro-Raman study of electronic properties of inversion domains in GaN-based lateral polarity heterostructures AU - Park, M AU - Cuomo, JJ AU - Rodriguez, BJ AU - Yang, WC AU - Nemanich, RJ AU - Ambacher, O T2 - JOURNAL OF APPLIED PHYSICS AB - The electronic properties of inversion domains in a GaN-based lateral polarity heterostructure were investigated using micro-Raman spectroscopy. The piezoelectric polarization of each domain was calculated from strain determined via Raman scattering. The free carrier concentration and electron mobility were deduced from the longitudinal optical phonon–plasmon coupled mode. The electron concentration in the N-face domain was slightly higher than that in the Ga-face domain. It appears that during growth, a larger number of donor impurities may have been incorporated into the N-face domain than into the Ga-face domain. DA - 2003/6/15/ PY - 2003/6/15/ DO - 10.1063/1.1570507 VL - 93 IS - 12 SP - 9542-9547 SN - 1089-7550 ER - TY - PAT TI - Methods of fabricating gallium nitride semiconductor layers on substrates including non-gallium nitride posts, and gallium nitride semiconductor structures fabricated thereby AU - Linthicum, K. J. AU - Gehrke, T. AU - Davis, R. F. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Methods of fabricating gallium nitride microelectronic layers on silicon layers AU - Linthicum, K. J. AU - Gehrke, T. AU - Davis, R. F. AU - Thomson, D. B. AU - Tracy, K. M. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Method for making optoelectronic and microelectronic devices including cubic ZnMgO and/or CdMgO alloys AU - Narayan, J. AU - Sharma, A. K. AU - Muth, J. F. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Lanthanum oxide-based gate dielectrics for integrated circuit field effect transistors AU - Maria, J.-P. AU - Kingon, A. I. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - JOUR TI - Influence of polymer conformation on the shear modulus and morphology of polyallylamine and poly(alpha-L-lysine) hydrogels AU - Oliveira, ED AU - Hirsch, SG AU - Spontak, RJ AU - Gehrke, SH T2 - MACROMOLECULES AB - Two polyamines with different conformational properties, poly(α-l-lysine) and polyallylamine, were chemically cross-linked to evaluate the effects of polypeptide secondary structures on gel properties. Both cationic gels are highly swollen at low pH and shrink as it increases primarily due to the reduction in of the concentration of associated counterions in the gel as its ionization decreases. Network shear moduli were determined under uniaxial compression. For the polyallylamine gels, the shear modulus (G) scales as φ20.31, where φ2 denotes the polymer volume fraction, over the entire pH range. This result is in favorable agreement with the G ∼ φ21/3 relationship predicted for networks of flexible chains. Poly(α-l-lysine) gels swollen below pH 11.0 obey the same scaling behavior. At higher pH levels, however, organized secondary structures are believed to develop, and the composition dependence of the modulus at high pH becomes consistent with the scaling relationship predicted for rigid-rod chain networks connected by flexible junctions (G ∼ φ23/2). Further evidence of the existence of more organized microstructures in the poly(α-l-lysine) gels at high pH is provided from complementary thermoelasticity and morphological analyses. DA - 2003/8/12/ PY - 2003/8/12/ DO - 10.1021/ma021468k VL - 36 IS - 16 SP - 6189-6201 SN - 1520-5835 ER - TY - PAT TI - High dielectric constant metal silicates formed by controlled metal-surface reactions AU - Parsons, G. N. AU - Chambers, J. J. AU - Kelly, M. J. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - JOUR TI - Helical-type surface defects in GaN thin films epitaxially grown on GaN templates at reduced temperatures AU - Miraglia, PQ AU - Preble, EA AU - Roskowski, AM AU - Einfeldt, S AU - Davis, RF T2 - JOURNAL OF CRYSTAL GROWTH AB - Surface pits in the form of v-shaped defects and resulting surface roughening, previously associated solely with InGaN films, were observed and investigated using atomic force microscopy on GaN films grown at 780°C via metalorganic vapor phase epitaxy on conventionally and pendeo-epitaxially deposited GaN thin film templates. The density of the v-shaped defects was similar to the density of threading dislocations of ∼3×109 cm−2 (that originate from the heteroepitaxial interface between the GaN template layer and the SiC substrate). Moreover, the v-defect density was diminished with decreases in the dislocation density via increases in the template layer thickness or the use of pendeo-epitaxial seed layers. A concomitant reduction in the full-width half-maxima of the X-ray rocking curves was also observed. A qualitative model is presented that describes the formation of v-shaped defects as a result of interactions between the movement of surface steps, screw-type dislocation cores, and clusters of atoms on the terraces that form under conditions of high surface undercooling. DA - 2003/6// PY - 2003/6// DO - 10.1016/S0022-0248(03)00970-9 VL - 253 IS - 1-4 SP - 16-25 SN - 1873-5002 KW - atomic force microscopy KW - growth models KW - line defects KW - surface defects KW - metalorganic vapor phase epitaxy KW - gallium nitride ER - TY - PAT TI - Gallium nitride semiconductor structures including lateral gallium nitride layers AU - Davis, R. F. AU - Nam, O.-H. AU - Zheleva, T. AU - Bremser, M. D. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Gallium nitride semiconductor structure including laterally offset patterned layers AU - Davis, R. F. AU - Nam, O.-H. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - JOUR TI - Formation of nanoscale voids and related metallic impurity gettering in high-energy ion-implanted and annealed epitaxial silicon AU - Kvit, A AU - Yankov, RA AU - Duscher, G AU - Rozgonyi, G AU - Glasko, JM T2 - APPLIED PHYSICS LETTERS AB - We have examined nanovoid formation, Fe gettering, and Fe clustering phenomena occurring in epitaxial silicon layers implanted with MeV Si ions. Insights into these phenomena as a function of depth have been gained from detailed analyses by Z-contrast imaging in conjunction with electron energy-loss spectroscopy. Our work has shown at the nanoscale structural and chemical levels that the defects produced by MeV self-ion implantation between the surface and the ion projected range Rp (i.e., in the so-called Rp/2 region) are voids, which provide extremely efficient and aggressive metallic impurity gettering. It has been proposed that the gettering does not occur via chemisorption or silicidation layering on the internal surface of the void walls, as in the well-known case of helium-induced cavities, but rather proceeds in a mode of metal–metal atom binding in the vicinity of the Rp/2 voids. DA - 2003/8/18/ PY - 2003/8/18/ DO - 10.1063/1.1601678 VL - 83 IS - 7 SP - 1367-1369 SN - 0003-6951 ER - TY - JOUR TI - Electrical characterization of InGaN quantum well p-n heterostructures AU - Gonzalez, JC AU - Silva, MIN AU - Bunker, KL AU - Batchelor, AD AU - Russell, PE T2 - MICROELECTRONICS JOURNAL AB - In this work, two methods for electrical characterization of InGaN quantum well p–n heterostructures at the nanometer level are presented. Cross-sectional Electrical Force Microscopy and High Resolution Electron Beam Induced Current (HR-EBIC) are used to study and identify regions of the cross-sectional surface of InGaN heterostructures with different types of electrical conductivity, the location of the InGaN quantum well, the location of the p–n junction, and the depletion layer. HR-EBIC was implemented in a Scanning Transmission Electron Microscope to take advantage of the high resolution chemical imaging capabilities of this microscope, such as Z-Contrast and Energy Dispersive X-ray Spectroscopy, and the small spread of the high energy electron beam in the electron transparent thin sample that allows electron beam induced current imaging with nanometer resolution. DA - 2003/// PY - 2003/// DO - 10.1016/S0026-2692(03)00072-7 VL - 34 IS - 5-8 SP - 455-457 SN - 0026-2692 KW - InGaN KW - electrical force microscopy KW - p-n heterostructure ER - TY - JOUR TI - Cross-sectional Scanning Probe Microscopy of GaN-based p-n heterostructures AU - Silva, MIN AU - Gonzalez, JC AU - Russell, PE T2 - MICROELECTRONICS JOURNAL AB - In this work, the structural and electrical properties of a GaN-based p–n heterostructure are studied using cross-sectional Atomic Force Microscopy, Friction Force Microscopy, Electrical Force Gradient Microscopy, and Surface Potential Microscopy. Using Atomic Force Microscopy and Friction Force Microscopy, we were able to identify and measure the thickness of the layers present in the heterostructures. The electrical conductivity type of the different layers as well as the p–n junction, and piezoelectric fields were identified and studied using Electric Force Gradient Microscopy and Surface Potential Microscopy. DA - 2003/// PY - 2003/// DO - 10.1016/S0026-2692(03)00051-X VL - 34 IS - 5-8 SP - 571-573 SN - 0026-2692 KW - GaN-based p-n heterostructure KW - Scanning Probe Microscopy KW - Electric Force Gradient Microscopy ER - TY - JOUR TI - Controlled synthesis of novel metalated poly(aminohexyl)-(aminopropyl)silsesquioxane colloids AU - Bronstein, LM AU - Linton, CN AU - Karlinsey, R AU - Ashcraft, E AU - Stein, BD AU - Svergun, DI AU - Kozin, M AU - Khotina, IA AU - Spontak, RJ AU - Werner-Zwanziger, U AU - Zwanziger, JW T2 - LANGMUIR AB - A new family of polysilsesquioxanes colloids was synthesized by hydrolytic condensation of a functionalized precursor N-(6-aminohexyl)aminopropyltrimethoxysilane (AHAPS), H2N(CH2)6NHCH2CH2CH2Si(OCH3)3, and studied using small-angle X-ray scattering, transmission electron microscopy, liquid and solid state NMR, elemental analysis, and other methods. The PAHAPS (polymerized AHAPS) structure is highly functionalized and its functionality can be varied by protonation of the amino groups. This allows varying the local ordering in the PAHAPS colloids, including formation of highly ordered lamellar structures when the AHAPS precursor is hydrolyzed in pure water. By varying the type of solvent (water or THF), one can vary the macrostructure and properties (for example, to impart colloidal solubility) of PAHAPS. These features make PAHAPS a robust polymer material synthesized in a one-pot reaction procedure. As amino groups (protonated or not) easily interact with the majority of transition-metal compounds, PAHAPS colloids can template a variety of particles of interest: magnetic, semiconductor, metal, or metal oxides with a small variation in the synthetic procedure. Here, formation of narrowly distributed discrete Pt nanoparticles packed within PAHAPS colloids (Pt content reaching 36 wt % without particle agglomeration) is described. The dependence of Pt nanoparticle and PAHAPS colloid sizes on metal compound and reducing agent types is demonstrated. DA - 2003/8/19/ PY - 2003/8/19/ DO - 10.1021/la034291b VL - 19 IS - 17 SP - 7071-7083 SN - 0743-7463 ER - TY - PAT TI - Chemically enhanced focused ion beam micro-machining of copper AU - Russell, P. E. AU - Griffis, D. P. AU - Gonzales Perez, J. C. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - JOUR TI - Bonding and structure of ultrathin yttrium oxide films for Si field effect transistor gate dielectric applications AU - Ulrich, MD AU - Rowe, JE AU - Niu, D AU - Parsons, GN T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Soft x-ray photoelectron spectroscopy using synchrotron radiation has been employed to study the interface between Y2O3 films and Si(100). Y2O3 films of ∼8, ∼15, and 65 Å were formed by plasma assisted chemical vapor deposition on HF-last Si(100). With this deposition technique, SiO2 forms at the interface and a kinetically limited silicate layer forms between the resulting SiO2 deposited Y2O3. For 65 Å films, the Y 3d5/2 binding energy was between 158.8 and 159.0 eV, 2.2–2.4 eV higher than the reported value of 156.6 eV for Y2O3. For 8 and 15 Å films, the Y 3d5/2 binding energies were 159.6 and 158.9 eV, respectively. The relatively high binding energies are attributed to hydroxide incorporation in the film. For the ultrathin films, ∼10 Å of SiO2 was formed at the interface during or after the deposition. For the 8 Å film, no silicate is detectable whereas for the 15 Å film, an estimated 4 Å of silicate is present between the interfacial SiO2 and Y2O3 overlayer. Because this transition layer does not form in the 8 Å film, it is concluded that the mixing is kinetically limited. For the 8 Å film, the Si 2p3/2 [SiO2] binding energy was 3.65 eV relative to the substrate peak. For the 15 Å deposition, the Si 2p3/2 [SiO2] binding energy was 3.44 eV and the Si 2p3/2 [silicate] binding energy was 2.65 eV relative to the substrate peak. DA - 2003/// PY - 2003/// DO - 10.1116/1.1593647 VL - 21 IS - 4 SP - 1792-1797 SN - 1071-1023 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000185080000113&KeyUID=WOS:000185080000113 ER - TY - PAT TI - Binary non-crystalline oxide analogs of silicon dioxide for use in gate dielectrics AU - Lucovsky, G. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - JOUR TI - Application of the simplified bond-hyperpolarizability model to fourth-harmonic generation AU - Hansen, JK AU - Peng, HJ AU - Aspnes, DE T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - We show that the simplified bond-hyperpolarizability model (SBHM), previously used to accurately describe anisotropies observed in second-harmonic generation from Si–dielectric interfaces, also describes anisotropies observed in fourth-harmonic generation (FHG). FHG data from (001)Si–SiO2 interfaces show two contributions: one from the intrinsic response of the interface bonds and the second from roughness. SBHM calculations yield excellent agreement with scaled ps and ss polarization data and the phases of the pp and sp equivalents with no adjustable parameters. The SHBM also precisely reproduces the anisotropy data for samples with systematic variations of interface roughness, and predicts relative amplitudes consistent with measured fields to factors of about 2. DA - 2003/// PY - 2003/// DO - 10.1116/1.1593057 VL - 21 IS - 4 SP - 1798-1803 SN - 1071-1023 ER - TY - JOUR TI - Aberration-corrected scanning transmission electron microscopy: the potential for nano- and interface science AU - Pennycook, S. J. AU - Lupini, A. R. AU - Kadavanich, A. AU - Mcbride, J. R. AU - Rosenthal, S. J. AU - Puetter, R. C. AU - Yahil, A. AU - Krivanek, O. L. AU - Dellby, N. AU - Nellist, P. D. L. AU - Duscher, G. AU - Wang, L. G. AU - Pantelides, S. T. T2 - Zeitschrift fur MetallkundeAmerican Journal of Physiology DA - 2003/// PY - 2003/// VL - 94 IS - 4 SP - 350-357 ER - TY - JOUR TI - Thermal stability of TaSixNy films deposited by reactive sputtering on SiO2 AU - Suh, YS AU - Heuss, GP AU - Misra, V AU - Park, DG AU - Limb, KY T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - The thermal stability of /p-type Si metal-insulator-semiconductor structure has been evaluated by measuring equivalent oxide thickness (EOT) from capacitance-voltage curves and gate leakage current as a function of annealing temperatures. films were deposited using reactive sputtering from a target, varying the nitrogen/argon flow ratio. A reaction between and was observed after a 1000°C anneal, resulting in the increase of interfacial roughness and oxide thickness in the structures. Cross-sectional transmission electron microscopy shows no indication of an interfacial reaction or crystallization in on up to 1000°C as manifested by the negligible change in EOT and the stable leakage currents density A/cm2 at V). The presence of Si-N bonds is attributed to cause the amorphous nature of the high N-containing films. This may retard the formation of an interface layer and improve the chemical-thermal stability of the gate electrode/dielectric interface and oxygen diffusion barrier properties under high-temperature annealing. © 2003 The Electrochemical Society. All rights reserved. DA - 2003/5// PY - 2003/5// DO - 10.1149/1.1562599 VL - 150 IS - 5 SP - F79-F82 SN - 1945-7111 ER - TY - JOUR TI - TaN-TiN binary alloys and superlattices as diffusion barriers for copper interconnects AU - Wang, H AU - Gupta, A AU - Tiwari, A AU - Zhang, X AU - Narayan, J T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 2003/10// PY - 2003/10// DO - 10.1007/s11664-003-0081-7 VL - 32 IS - 10 SP - 994-999 SN - 0361-5235 KW - TaN KW - TiN KW - superlattice KW - alloy KW - Cu diffusion barrier ER - TY - JOUR TI - Synthesis of nanostructured titania powders via hydrolysis of titanium isopropoxide in supercritical carbon dioxide AU - Stallings, WE AU - Lamb, HH T2 - LANGMUIR AB - Titania powders were synthesized via hydrolysis of titanium(IV) isopropoxide (TIP) in supercritical carbon dioxide (SCCD). Injection of TIP into water-in-CO2 (w/c) dispersions resulted in precipitation of spherical titania particles, and free-flowing white titania powders were isolated in 65−70% yield by slow isothermal depressurization. Qualitatively similar results were obtained with and without the addition of an anionic phosphate fluorosurfactant (DuPont Zonyl FSP) to stabilize the w/c dispersions. The titania powders had broad particle size distributions (20−800 nm) and specific surface areas in the 100−500 m2/g range. Addition of Zonyl FSP resulted in a decrease in specific surface area at a given water-to-alkoxide molar ratio (hydrolysis level). The specific surface area increased as the hydrolysis level was increased, irrespective of the presence of surfactant. The surface area is associated primarily with internal porosity of the spherical titania particles, as evidenced by scanning transmission electron microscopy and N2 porosimetry. Calcination of a surfactant-free titania powder at 300 °C in air decreased the specific surface area from ∼300 to 65 m2/g and increased the mean cylindrical pore diameter from 2.6 to 4.9 nm, consistent with collapse of micropores. Titania nanoparticle synthesis via TIP hydrolysis in SCCD was attempted using w/c microemulsions formed with ammonium carboxylate perfluoropolyether (PFPE-NH4); however, injection of TIP into PFPE-NH4-stabilized microemulsions resulted in precipitation of 0.3−2 μm titania particles. The use of other CO2-soluble titanium(IV) alkoxides gave qualitatively similar results. DA - 2003/4/1/ PY - 2003/4/1/ DO - 10.1021/la020760i VL - 19 IS - 7 SP - 2989-2994 SN - 0743-7463 ER - TY - JOUR TI - Photoelectron emission microscopy observation of inversion domain boundaries of GaN-based lateral polarity heterostructures AU - Yang, W. C. AU - Rodriguez, B. J. AU - Park, M. AU - Nemanich, R. J. AU - Ambacher, O. AU - Cimalla, V. T2 - Journal of Applied Physics AB - An intentionally grown GaN film with laterally patterned Ga- and N-face polarities is studied using in situ UV-photoelectron emission microscopy (PEEM). Before chemical vapor cleaning of the surface, the emission contrast between the Ga- and N-face polarities regions was not significant. However, after cleaning the emission contrast between the different polarity regions was enhanced such that the N-face regions exhibited increased emission over the Ga-face regions. The results indicate that the emission threshold of the N-face region is lower than that of the Ga face. Moreover, bright emission was detected from regions around the inversion domain boundaries of the lateral polarity heterostructure. The PEEM polarity contrast and intense emission from the inversion domain boundary regions are discussed in terms of the built-in lateral field and the surface band bending induced by the polarization bound surface charges. DA - 2003/// PY - 2003/// DO - 10.1063/1.1618355 VL - 94 IS - 9 SP - 5720-5725 ER - TY - JOUR TI - Nanofibrillar networks in poly(ethyl methacrylate) and its silica nanocomposites AU - Wilder, EA AU - Braunfeld, MB AU - Jinnai, H AU - Hall, CK AU - Agard, DA AU - Spontak, RJ T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - Recent advances in polymer materials design seek to incorporate functionality, enhance existing properties, and reduce weight without compromising mechanical properties or processability. While much attention has been drawn to the development of organic/inorganic hybrid nanocomposites modified with discrete siliceous nanoparticles (such as fumed/colloidal silica or organoclays), other opportunities exist for comparably enlightened materials design. Dibenzylidene sorbitol (DBS) is a sugar derivative that is capable of self-organizing into a 3D nanofibrillar network at relatively low concentrations in a wide variety of organic solvents and polymers. In this work, we explore the morphological characteristics and properties of DBS in poly(ethyl methacrylate) (PEMA) and PEMA nanocomposites with colloidal silica. Transmission electron microscopy and microtomography reveal that the DBS molecules form highly connected networks, with nanofibrils measuring ca. 10 nm in diameter and ranging up to several hundred nanometers in length. Dynamic mechanical property analysis reveals that, while DBS has little effect on glassy PEMA, it serves to increase the elastic modulus in molten PEMA. DA - 2003/10/23/ PY - 2003/10/23/ DO - 10.1021/jp035113u VL - 107 IS - 42 SP - 11633-11642 SN - 1520-6106 ER - TY - PAT TI - Methods of fabricating gallium nitride semiconductor layers by lateral overgrowth AU - Davis, R. F. AU - Nam, O.-H. AU - Zheleva, T. AU - Bremser, M. D. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Gallium nitride semiconductor structures fabricated by pendeoepitaxial methods of fabricating gallium nitride semiconductor layers on weak posts AU - Linthicum, K. J. AU - Gehrke, T. AU - Davis, R. F. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - JOUR TI - Effects of grain boundary on impurity gettering and oxygen precipitation in polycrystalline sheet silicon AU - Lu, JG AU - Wagener, M AU - Rozgonyi, G AU - Rand, J AU - Jonczyk, R T2 - JOURNAL OF APPLIED PHYSICS AB - The effects of grain boundaries (GB) in polycrystalline sheet silicon on impurity gettering and oxygen precipitation were investigated by electron beam induced current (EBIC), deep level transient spectroscopy (DLTS), micro-Fourier-transform infrared spectroscopy (FTIR), and preferential etching/Normaski optical microscopy techniques. Both as-grown and thermally processed wafers were studied. A correlation between GB density and transition metal concentration was quantitatively established by combining DLTS and EBIC studies. It was found that four deep levels arising from Fe–B, Fe–Al, Cr–B, and Fei were present in the as-grown sample, and their concentrations decrease with increasing GB density. GB gettering was further verified by the presence of an EBIC image contrast halo around the GB. Preferential etching also revealed a precipitate density of 2×107 cm−2 on the GB. After processing, a clearly defined oxygen precipitate denuded zone formed around the GB with the interstitial oxygen concentration [Oi] decreased from 14.4 to 2.2×1017 cm−3. Micro-FTIR showed that, for both processed and as-grown samples, more silicon oxynitride appears in the GB than in the intragrain region. Since nitrogen enhances oxygen precipitation, it is likely that nitrogen preferentially precipitated on the GB during the wafer formation process and resulted in a nitrogen depletion zone, where oxygen precipitation was further suppressed and a denuded zone formed. DA - 2003/7/1/ PY - 2003/7/1/ DO - 10.1063/1.1578699 VL - 94 IS - 1 SP - 140-144 SN - 0021-8979 ER - TY - JOUR TI - Convergence acceleration scheme for self-consistent orthogonal-basis-set electronic structure methods AU - Areshkin, DA AU - Shenderova, OA AU - Schall, JD AU - Brenner, DW T2 - MOLECULAR SIMULATION AB - A new self-consistent convergence acceleration scheme that is a variant of the Newton-Raphson algorithm for non-linear systems of equations is presented. With this scheme, which is designed for use with minimal orthogonal basis set electronic structure methods, the conventional Newton-Raphson scaling with respect to the number of atoms is enhanced from quartic to cubic. The scheme is demonstrated using a self-consistent environment-dependent tight binding model for hydrocarbons that allows an efficient and reasonably precise simulation of charge density distortions due to external electric fields, finite system sizes, and surface effects. In the case of a metallic system, self-consistency convergence starts at a high fictitious temperature, typically 1500 K. As the electron density approaches the self-consistent configuration the temperature is decreased. Typically, seven to nine iterations are required to achieve self-consistency in metallic systems to a final temperature of 300 K. For systems with a finite band gap the convergence may start at the target temperature so that temperature reduction is unnecessary, and typically two iterations are needed to achieve self-consistency. The convergence algorithm can handle extremely high applied fields and is very robust with respect to initial electron densities. DA - 2003/4// PY - 2003/4// DO - 10.1080/0892702031000092197 VL - 29 IS - 4 SP - 269-286 SN - 1029-0435 KW - convergence acceleration scheme KW - Newton-Raphson algorithm KW - self-consistent orthogonal-basis-set electronic structure method KW - HOMO-LUMO gap ER - TY - JOUR TI - Chemical, physical, and electrical characterizations of oxygen plasma assisted chemical vapor deposited yttrium oxide on silicon AU - Niu, D AU - Ashcraft, RW AU - Chen, Z AU - Stemmer, S AU - Parsons, GN T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - Understanding and controlling interface and bulk chemical stability of chemical vapor deposited high-k dielectrics is an important research issue. We report thin films deposited by oxygen plasma assisted chemical vapor deposition using two yttrium diketonate precursors. Unacceptable large hysteresis in capacitance-voltage data, presumably due to the incorporation of fluorine, is observed for the films from the F-containing precursor. For films deposited with the hydrogenated precursor and exposed to air after deposition, transmission electron microscopy shows a triple layer structure after annealing, and electron energy loss spectroscopy and X-ray photoelectron spectroscopy show the film to be stoichiometric on top and yttrium at dielectric/Si interface. This structure is also confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, and atomic force microscopy. Prenitridation of the silicon surface prior to dielectric deposition impedes the reaction with the substrate, promoting the structure. A substantial consumption of silicon substrate is directly demonstrated by a carefully designed etching experiment. Possible mechanisms consistent with the observed results, including Si diffusion, crystallization of and reaction with absorbed OH, are discussed. © 2003 The Electrochemical Society. All rights reserved. DA - 2003/5// PY - 2003/5// DO - 10.1149/1.1566415 VL - 150 IS - 5 SP - F102-F109 SN - 1945-7111 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000182184200051&KeyUID=WOS:000182184200051 ER - TY - JOUR TI - Band-gap dependence of field emission from one-dimensional nanostructures grown on n-type and p-type silicon substrates AU - Chang, CS AU - Chattopadhyay, S AU - Chen, LC AU - Chen, KH AU - Chen, CW AU - Chen, YF AU - Collazo, R AU - Sitar, Z T2 - PHYSICAL REVIEW B AB - Field emission of electrons from narrow-band-gap and wide-band-gap one-dimensional nanostructures were studied. N-type silicon substrates enhanced the emission from the low-band-gap silicon nanowires and carbon nanotubes, whereas p-type substrates were a better choice for field emission from wide-band-gap silicon carbon nitride nanocrystalline thin films and nanorods. The role of the substrate-nanostructure interface was modeled based on different junction mechanisms to explain, qualitatively, the fundamentally different emission behavior of these nanostructures when n- and p-type silicon substrates were used. The results could be explained on the basis of simple carrier transport across the silicon-silicon nanowire interface and subsequent tunneling of electrons for the silicon nanowires. Schottky barrier theory can explain the better field emission of electrons from the n-type silicon supported carbon nanotubes. The decreased barrier height at the interface of the silicon-silicon carbon nitride heterojunction, when p-type silicon substrate was used, could explain the superior field emission in comparison to when n-type silicon substrates were used. DA - 2003/9/15/ PY - 2003/9/15/ DO - 10.1103/physrevb.68.125322 VL - 68 IS - 12 SP - SN - 1098-0121 ER - TY - JOUR TI - Attractive migration and coalescence: A significant process in the coarsening of TiSi2 islands on the Si(111) surface AU - Yang, WC AU - Zeman, M AU - Ade, H AU - Nemanich, RJ T2 - PHYSICAL REVIEW LETTERS AB - The dynamics and coarsening of TiSi2 islands on Si(111) surfaces are studied in real time with photoelectron emission microscopy. A significant fraction of events are observed in which nearby islands move attractively toward each other and subsequently coalesce. It is proposed that attractive island migration is due to the growth-decay flow of the island edges driven by a nonuniform surface concentration around the islands. The local surface concentration is induced by the neighboring islands. This coarsening mechanism should significantly affect the evolution of the island distribution. DA - 2003/4/4/ PY - 2003/4/4/ DO - 10.1103/physrevlett.90.136102 VL - 90 IS - 13 SP - SN - 0031-9007 ER - TY - JOUR TI - Sorption, transport, and structural evidence for enhanced free volume in poly(4-methyl-2-pentyne)/fumed silica nanocomposite membranes AU - Merkel, TC AU - Freeman, BD AU - Spontak, RJ AU - He, Z AU - Pinnau, I AU - Meakin, P AU - Hill, AJ T2 - CHEMISTRY OF MATERIALS AB - In contrast to the performance of traditional filled polymer systems, penetrant permeability coefficients in high-free-volume, glassy poly(4-methyl-2-pentyne) (PMP) increase systematically and substantially with increasing concentration of nonporous, nanoscale fumed silica (FS). For instance, the permeability of PMP containing 40 wt % FS to methane is 2.3 times higher than that of the unfilled polymer. Gas and vapor uptake in the PMP/FS nanocomposites is essentially unaffected by the presence of up to 40 wt % FS, while penetrant diffusion coefficients increase regularly with increasing filler content. This increase in diffusivity is responsible for elevated permeability in the PMP/FS nanocomposites. The addition of FS to PMP augments the permeability of large penetrants more than that of small gases, consistent with a reduction in diffusivity selectivity. Consequently, vapor selectivity in the nanocomposites increases with increasing FS concentration. Activation energies of permeation in PMP decrease with increasing FS content, suggesting that penetrant diffusive jumps require less energy at higher filler concentrations. Positron annihilation lifetime spectroscopy (PALS) reveals that FS subtly increases the free volume in PMP available for molecular transport. The accessible free volume measured by PALS correlates favorably with relative penetrant permeability in the nanocomposites. Transmission electron microscopy confirms that the FS nanoparticles are relatively well dispersed in PMP. DA - 2003/1/14/ PY - 2003/1/14/ DO - 10.1021/cm020672j VL - 15 IS - 1 SP - 109-123 SN - 0897-4756 ER - TY - JOUR TI - Properties of La-silicate high-K dielectric films formed by oxidation of La on silicon AU - Gougousi, T AU - Kelly, MJ AU - Terry, DB AU - Parsons, GN T2 - JOURNAL OF APPLIED PHYSICS AB - In this article, we present data on the properties of La-based high-k dielectric films prepared by oxidation of La deposited by physical vapor deposition on silicon. Films are characterized by x-ray photoelectron spectroscopy, infrared absorption, and capacitance versus voltage analysis. We find that when we oxidize La metal sputter deposited on Si substrates, it reacts with the silicon substrate to form La silicate. La films as thick as 300 Å will react completely with Si under moderate oxidation conditions (900 °C for 10 min) suggesting a very rapid silicidation reaction between La and Si. Under some processing conditions the as-deposited films contain a small La2O3 component that reduces to La silicate upon anneal at high temperatures. La-silicate films do not phase separate into La2O3 and SiO2 upon annealing at 1050 °C, and their resistance to H2O incorporation depends critically on the oxidation temperature. Electrical measurements show a high concentration of positive fixed charge. DA - 2003/2/1/ PY - 2003/2/1/ DO - 10.1063/1.1531818 VL - 93 IS - 3 SP - 1691-1696 SN - 1089-7550 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000180630200056&KeyUID=WOS:000180630200056 ER - TY - JOUR TI - Preparation and characterization of atomically clean, stoichiometric surfaces of n- and p-type GaN(0001) AU - Tracy, KM AU - Mecouch, WJ AU - Davis, RF AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - It is demonstrated that in situ exposure of the (0001) surface of n- and p-type GaN thin films to flowing ammonia at 860 °C and 10−4 Torr removes hydrocarbon and oxygen/hydroxide species below the detectable limits of x-ray and ultraviolet photoelectron spectroscopies (UPS) and decreases the Ga/N ratio from 1.3 to 1.0. Additional indications of the efficacy of this ammonia-based chemical vapor cleaning (CVC) process were the shifts in the Ga 3d and the N 1s core level positions from the as-loaded to the CVC surfaces of the n-type samples from 21.0±0.1 to 20.6±0.1 eV and from 398.3±0.1 to 398.0±0.1 eV, respectively, and the change in the UPS measured low energy spectrum turn on from 3.9±0.1 (as-loaded samples) to 3.0±0.1 eV (cleaned samples) below the Fermi level. Analogous changes in the p-type samples were from 19.6±0.1 to 18.9±0.1 eV and from 397.1±0.1 to 396.3±0.1 eV for the Ga 3d and the N 1s core levels, and from 3.0±0.1 to 1.1±0.1 eV for the UPS valence band maximum (VBM). The VBM values of the CVC samples indicate band bending of ∼0.3 eV upward on n type and ∼0.8 eV downward on p type. Electron affinities of 2.8±0.1 and 2.6±0.1 eV were determined for the clean n-type and p-type surfaces, respectively. Irrespective of doping, the CVC process left unchanged the (1×1) low energy diffraction pattern, the terraced microstructure, and the root mean square roughness observed for the surfaces of the as-loaded samples, i.e., the surface microstructure was not damaged during the high temperature exposure to ammonia at low pressure. DA - 2003/9/1/ PY - 2003/9/1/ DO - 10.1063/1.1596369 VL - 94 IS - 5 SP - 3163-3172 SN - 1089-7550 ER - TY - JOUR TI - On the origin and energy of triple junction defects due to the finite length of grain boundaries AU - Nazarov, AA AU - Bachurin, DV AU - Shenderova, OA AU - Brenner, DW T2 - INTERFACE SCIENCE DA - 2003/10// PY - 2003/10// DO - 10.1023/A:1026143927269 VL - 11 IS - 4 SP - 417-424 SN - 0927-7056 KW - grain boundary KW - triple junction KW - grain boundary dislocation KW - disclination KW - nanocrystal ER - TY - JOUR TI - High performance 0.14 mu m gate-length AlGaN/GaN power HEMTs on SiC AU - Jessen, GH AU - Fitch, RC AU - Gillespie, JK AU - Via, GD AU - Moser, NA AU - Yannuzzi, MJ AU - Crespo, A AU - Sewell, JS AU - Dettmer, RW AU - Jenkins, TJ AU - Davis, RF AU - Yang, J AU - Khan, MA AU - Binari, SC T2 - IEEE ELECTRON DEVICE LETTERS AB - High electron mobility transistors (HEMTs) were fabricated from AlGaN/GaN on semi-insulating SiC substrates with excellent performance and high yield. The devices had 0.14 μm T-gates with a total width of 300 μm. Extrinsic, unpassivated peak performance values for these HEMTs include transconductance of 338 mS/mm, maximum drain current of 1481 mA/mm, unity current gain cutoff frequency of 91 GHz, and maximum frequency of oscillation of 122 GHz. Saturated CW power measurements of these devices at 10 GHz result in 4.6 W/mm with PAE at 46% when optimized for power and 3.0 W/mm with PAE at 65% when optimized for efficiency. DA - 2003/11// PY - 2003/11// DO - 10.1109/LED.2003.818816 VL - 24 IS - 11 SP - 677-679 SN - 0741-3106 KW - GaN KW - high electron mobility transistor (HEMT) KW - power KW - SiC ER - TY - JOUR TI - Growth, characterization,, and electrical properties of PbZr0.52Ti0.48O3 thin films on buffered silicon substrates using pulsed laser deposition AU - Gilmore, WM AU - Chattopadhyay, S AU - Kvit, A AU - Sharma, AK AU - Lee, CB AU - Collis, WJ AU - Sankar, J AU - Narayan, J T2 - JOURNAL OF MATERIALS RESEARCH DA - 2003/1// PY - 2003/1// DO - 10.1557/JMR.2003.0016 VL - 18 IS - 1 SP - 111-114 SN - 0884-2914 ER - TY - JOUR TI - Field emission characterization of silicon tip arrays coated with GaN and diamond nanoparticle clusters AU - Hajra, M AU - Chubun, NN AU - Chakhovskoi, AG AU - Hunt, CE AU - Liu, K AU - Murali, A AU - Risbud, SH AU - Tyler, T AU - Zhirnov, V T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Wide band-gap materials show promise for applications in coating of field emission tips. Recently nanocrystalline hexagonal GaN crystallites as small as 12 nm average diameter have been formed using reactive laser ablation of gallium metal in nitrogenating ambient [T. J. Goodwin et al., Appl. Phys. Lett. 70, 3122 (1997)]. In this article we investigated the performance of ungated emitters with and without surface coating. Silicon tip arrays are coated by dielectrophoresis of gallium nitride nanoparticles or nanocrystalline diamond clusters from an ethanol suspension. The emitters were evaluated and compared before and after the surface treatment using SEM image and I–V measurements in the diode configuration. The results suggest that the emitters benefit from coating the surface with nanocrystalline diamond clusters in terms of reduction in the turn on voltage by 100 V and increase uniformity in emission during low voltage operation. The long-term emission stability for both types of the coated cathodes was studied over a period of 90 h. The emitters coated with GaN nanoparticle clusters show a significant improvement in the current fluctuation from 150% (for untreated cathodes) to 50%. DA - 2003/// PY - 2003/// DO - 10.1116/1.1540986 VL - 21 IS - 1 SP - 458-463 SN - 1071-1023 ER - TY - JOUR TI - Electron emission from diamond nanoparticles on metal tips AU - Tyler, T AU - Zhirnov, , VV AU - Kvit, AV AU - Kang, D AU - Hren, JJ T2 - APPLIED PHYSICS LETTERS AB - Single-crystalline diamond nanoparticles (∼5 nm in scale) have been deposited onto molybdenum needles (with radii &lt;100 nm), and their effects on field emission behavior were measured. Combined transmission electron microscopy observations, field emission measurements, and diamond depositions allowed for direct comparison of the effects of various amounts of nanodiamond coating on the field emission properties of a coated metal field emitter. In the limit, field emission from a single isolated diamond nanoparticle is compared here with that from an uncoated metal emitter and from a coating comprised of several layers of nanoparticles. DA - 2003/4/28/ PY - 2003/4/28/ DO - 10.1063/1.1570498 VL - 82 IS - 17 SP - 2904-2906 SN - 0003-6951 ER - TY - JOUR TI - Carbonate formation during post-deposition ambient exposure of high-k dielectrics AU - Gougousi, T AU - Niu, D AU - Ashcraft, RW AU - Parsons, GN T2 - APPLIED PHYSICS LETTERS AB - When thick films of group-III (La, Y)- and group-IV (Hf, Zr)-based high-k dielectrics are exposed to ambient for several months, Fourier transform infrared spectroscopy shows formation of carbonate species in the film bulk, likely due to reaction with atmospheric CO2. Group-III-based films show signs of carbonate feature growth within 10 min of air exposure, especially in films processed at relatively low temperatures (&lt;600 °C). Carbonate formation is verified also for group-IV-based films, but at a significantly reduced concentration. Post-exposure annealing can reduce the carbonate observed in the IR spectra. However, post-exposure annealing likely does not remove carbon contamination, and it results in interface silicon oxide growth. The observed reactions of high-k films with the ambient may impose significant constraints on the post-deposition handling of high-k films. DA - 2003/10/27/ PY - 2003/10/27/ DO - 10.1063/1.1623316 VL - 83 IS - 17 SP - 3543-3545 SN - 0003-6951 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000186068400033&KeyUID=WOS:000186068400033 ER - TY - JOUR TI - Band offset measurements of the GaN (0001)/HfO2 interface AU - Cook, T. E. AU - Fulton, C. C. AU - Mecouch, W. J. AU - Davis, R. F. AU - Lucovsky, G. AU - Nemanich, R. J. T2 - Journal of Applied Physics DA - 2003/// PY - 2003/// DO - 10.1063/1.1618374 VL - 94 IS - 11 SP - 7155-7158 ER - TY - JOUR TI - Supersonic jet epitaxy of gallium nitride using triethylgallium and ammonia AU - McGinnis, AJ AU - Thomson, D AU - Banks, A AU - Preble, E AU - Davis, RF AU - Lamb, HH T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Gallium nitride (GaN) films were grown on GaN(0001)/AlN/6H–SiC composite substrates at 700–780 °C by supersonic jet epitaxy using triethylgallium (TEG) and NH3. TEG was seeded in He and N2 supersonic free jets to obtain kinetic energies of ∼2.1 and ∼0.5 eV, respectively, and NH3 was supplied from a variable leak valve. Higher TEG beam intensities (by about a factor of 5) were obtained by seeding in He. In situ reflection high-energy electron diffraction indicated a transition from three-dimensional to two-dimensional (2D) growth between 730 and 750 °C for films grown using TEG seeded in He and a constant NH3/TEG flux ratio. Ex situ atomic force microscopy of films grown at 730 and 750 °C revealed smooth surfaces comprised of quasi-2D islands with irregular perimeters. Cross-sectional transmission electron microscopy evidenced that the film grown at 750 °C was homoepitaxial α-GaN with a high density of planar lattice defects. Secondary ion mass spectrometry detected high residual carbon concentrations in the films. The GaN growth rate at 750 °C was found to depend on TEG flux and NH3 pressure in a manner consistent with Langmuir–Hinshelwood kinetics. Films grown under NH3-rich conditions were faceted and microscopically rough, whereas nonfaceted, basal-plane growth was observed under Ga-rich conditions. The first-order dependence of growth rate on TEG flux under NH3-rich conditions was used to estimate Ga incorporation efficiencies for high- and low-energy TEG beams. The Ga incorporation efficiency is lower for high-energy TEG beams, consistent with a decrease in the sticking coefficient for dissociative chemisorption. DA - 2003/// PY - 2003/// DO - 10.1116/1.1532736 VL - 21 IS - 1 SP - 294-301 SN - 0734-2101 ER - TY - JOUR TI - Spatial inhomogeneity of imprint and switching behavior in ferroelectric capacitors AU - Gruverman, A AU - Rodriguez, BJ AU - Kingon, AI AU - Nemanich, RJ AU - Cross, JS AU - Tsukada, M T2 - APPLIED PHYSICS LETTERS AB - Piezoresponse force microscopy has been used to perform nanoscale characterization of the spatial variations in the imprint and switching behavior of (111)-oriented Pb(Zr,Ti)O3-based capacitors on Pt electrodes. Mapping of polarization distribution in the poled capacitors as well as local d33–V loop measurements revealed a significant difference in imprint and switching behavior between the peripheral and inner parts of the capacitors. It has been found that the inner regions of the capacitors are negatively imprinted (with the preferential direction of the normal component of polarization upward) and tend to switch back after application of the positive poling voltage. On the other hand, switchable regions at the edge of the integrated capacitors generally exhibit more symmetric hysteresis behavior. Application of an ac switching voltage, contrary to what was expected, resulted in an increase of the negatively imprinted regions. The observed effect has been explained by incomplete or asymmetric switching due to the mechanical stress conditions existing in the central parts of the capacitors. DA - 2003/5/5/ PY - 2003/5/5/ DO - 10.1063/1.1570942 VL - 82 IS - 18 SP - 3071-3073 SN - 0003-6951 ER - TY - JOUR TI - Spatial distribution of electron emission sites for sulfur doped and intrinsic nanocrystalline diamond films AU - Kock, FAM AU - Garguilo, JM AU - Nemanich, RJ AU - Gupta, S AU - Weiner, BR AU - Morell, G T2 - DIAMOND AND RELATED MATERIALS AB - We have investigated high sp2 content intrinsic and sulfur doped nanocrystalline diamond films to study field emission properties by electron emission microscopy operated in different modes. Electron emission microscopy enables real time imaging of the electron emission from a surface with a lateral resolution of ∼15 nm. The nanocrystalline intrinsic diamond films exhibit electron emission at room temperature from localized emission sites with weak temperature dependence, and a density of ∼103–104/cm2. In contrast, sulfur doped diamond films show similar emission characteristics at room temperature, but at elevated temperatures the emission significantly increases from the localized regions and a thermionic component is identified in the I/V dependence. We discuss the role of S-donor states to explain the enhanced emission of the S-doped nanocrystalline diamond. DA - 2003/// PY - 2003/// DO - 10.1016/S0925-9635(02)00365-5 VL - 12 IS - 3-7 SP - 474-480 SN - 1879-0062 KW - nanocrystalline KW - plasma CVD KW - field emission ER - TY - JOUR TI - Solvent-facilitated homopolymer sorption in swollen block copolymer matrices AU - Stevens, JE AU - Thongruang, W AU - Patel, NP AU - Smith, SD AU - Spontak, RJ T2 - MACROMOLECULES AB - Homopolymer sorption in microphase-ordered block copolymers can provide insight into the factors governing transport of chain molecules in dense nanostructured environments, as well as yield novel nonequilibrium materials. Here, we examine the sorption of homopolymer B (hB) in ABA triblock copolymers swollen in a B-selective solvent. Gravimetric analysis reveals that the solubility of hB (ShB) varies linearly with solution concentration (C) and that (∂ShB/∂C)T depends on the molecular weight of the B midblock (MB). These data also show that the effective diffusion coefficient of hB is ∼10-8 cm2/s, independent of MB. DA - 2003/5/6/ PY - 2003/5/6/ DO - 10.1021/ma0215868 VL - 36 IS - 9 SP - 3206-3209 SN - 1520-5835 ER - TY - JOUR TI - Schottky-barrier behavior of metals on n- and p-type 6H-SiC AU - Aboelfotoh, M. O. AU - Frojdh, C. AU - Petersson, C. S. T2 - Physical Review. B, Condensed Matter and Materials Physics DA - 2003/// PY - 2003/// VL - 67 IS - 7 SP - 075312-1 ER - TY - JOUR TI - Role of silver addition in the synthesis of high critical current density MgB2 bulk superconductors AU - Kumar, D AU - Pennycook, SJ AU - Narayan, J AU - Wang, H AU - Tiwari, A T2 - SUPERCONDUCTOR SCIENCE & TECHNOLOGY AB - Ag-doped MgB2 bulk superconductors have been prepared using a standard solid state processing. The addition of Ag to MgB2 powders during the sintering process has been found to result in an important advantage, namely, the prevention/reduction of loss of Mg, a problem most commonly observed in the sintering of MgB2 bulk samples at elevated temperature and ambient pressures. The Ag-doped MgB2 sample has a distinct superconducting transition temperature around 39 K, while the undoped MgB2 undergoes only a very feeble transition to a diamagnetic superconducting state at around 39 K. The normal conducting silver regions in the MgB2 matrix act as pinning centres resulting in the realization of high critical currents in the presence of magnetic fields. DA - 2003/4// PY - 2003/4// DO - 10.1088/0953-2048/16/4/306 VL - 16 IS - 4 SP - 455-458 SN - 0953-2048 ER - TY - JOUR TI - Role of self-assembled gold nanodots in improving the electrical and optical characteristics of zinc oxide films AU - Tiwari, A AU - Chugh, A AU - Jin, C AU - Narayan, J T2 - JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY AB - We have studied the effect of embedding nanocrystalline Au particles on the electrical and optical characteristics of ZnO films. Au-embedded epitaxial ZnO films were deposited on (0001) sapphire substrates with a pulsed laser deposition technique. The crystalline quality of both the ZnO matrix and Au nanoparticles was investigated by X-ray diffraction and transmission electron microscopy. Composite films were characterized by photoluminescence, optical absorption, and low-temperature electrical resistivity measurements. Photoluminescence spectra of theses films showed a sharp excitonic peak at 3.22 +/- 0.05 eV without any signature of green band emission. Electrical resistivity measurements showed these films to be highly conducting, with a room-temperature resistivity of 3.4 +/- 0.2 m omega-cm. DA - 2003/10// PY - 2003/10// DO - 10.1166/jnn.2003.217 VL - 3 IS - 5 SP - 368-371 SN - 1533-4880 KW - ZnO KW - gold nanodots KW - plasmon resonance KW - photoluminescence KW - green band emission KW - pulsed laser deposition ER - TY - JOUR TI - Pulse current electrodeposition of nanocrystalline zinc AU - Saber, K. AU - Koch, C. C. AU - Fedkiw, P. S. T2 - Materials Science & Engineering. A, Structural Materials: Properties, Microstructure and Processing AB - Pulse electrodeposition exhibits marked advantages over direct current electrodeposition in the control of deposit grain size, surface morphology, and preferred orientation. The effect of pulse peak current density (Jp) on the grain size and surface morphology of zinc deposits with additives (polyacrylamide and thiourea) was studied by scanning electron microscopy and field emission scanning electron microscopy. The preferred orientation of zinc deposits was studied by X-ray diffraction, and microhardness of the deposits was measured by a Knoop microhardness tester. Increasing JP dramatically changed the surface morphology and decreased the grain size. Nanocrystalline zinc (56 nm) was produced at JP=2 A cm−2. At JP equal to 0.4 A cm−2, the preferred orientation of zinc deposits was (112̄2) and changed to the prismatic (112̄0) orientation at Jp equal to 0.8, 1.2, and 1.6 A cm−2. However, increasing the peak current density to 2 A cm−2 altered the prismatic (112̄0) to the random (101̄1). The microhardness increased to approximately 8 times higher than that of pure polycrystalline zinc (0.29 GPa). Microhardness reached a maximum (2.3 GPa) at 1.6 A cm−2, then decreased to 1.5 GPa at 2 A cm−2. The hardness drop was correlated with the presence of additives and the change in texture from (112̄0) to the random (101̄1) with increasing Jp. DA - 2003/// PY - 2003/// DO - 10.1016/s0921-5093(02)00198-3 VL - 341 IS - 1-2 SP - 174-181 ER - TY - JOUR TI - Phase behavior of poly(methyl methacrylate)/poly(vinylidene fluoride) blends in the presence of high-pressure carbon dioxide AU - Walker, TA AU - Melnichenko, YB AU - Wignall, GD AU - Lin, JS AU - Spontak, RJ T2 - MACROMOLECULAR CHEMISTRY AND PHYSICS AB - Abstract Previous efforts have demonstrated that high‐pressure CO 2 can markedly influence the phase behavior of amorphous polymer blends. In this work, we examine the effect of high‐pressure CO 2 on the miscibility of blends composed of glassy poly(methyl methacrylate) (PMMA) and semicrystalline poly(vinylidene fluoride) (PVDF). Blends of this type are known to exhibit lower critical solution temperature (LCST) behavior with partial miscibility up to ≈50–60 wt.‐% PVDF at ambient conditions. Two miscible PMMA/PVDF blends have been systematically exposed to high‐pressure CO 2 at 35 °C and pressures below and above the critical pressure. Small‐angle X‐ray scattering reveals that the scattering intensity at high scattering angles shows little dependence on pressure at low CO 2 pressures, but increases substantially at relatively high CO 2 pressures. Transmission electron microscopy and differential scanning calorimetry analyses confirm that the blends are initially quasi‐homogeneous with diffuse PVDF‐rich dispersions and a single glass transition temperature. After exposure to relatively high CO 2 pressures, however, the PVDF is found to crystallize within the PMMA‐rich matrix. Thermal recycling of these blends promotes homogenization, indicating that such CO 2 ‐altered phase behavior is reversible. SAXS patterns acquired from the 69/31 w/w PMMA/PVDF blend. magnified image SAXS patterns acquired from the 69/31 w/w PMMA/PVDF blend. DA - 2003/11/12/ PY - 2003/11/12/ DO - 10.1002/macp.200350075 VL - 204 IS - 17 SP - 2064-2077 SN - 1521-3935 KW - blends KW - high-pressure CO2 KW - phase miscibility KW - SAXS ER - TY - JOUR TI - Nanoindentation characterization of surface layers of electrical discharge machined WC-Co AU - Qu, J AU - Riester, L AU - Shih, AJ AU - Scattergood, RO AU - Lara-Curzio, E AU - Watkins, TR T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - This study applies nanoindentation and other analysis techniques to investigate the influence of wire electrical discharge machining (EDM) process on the structure and properties of machined surface layers of WC–Co composites. Multiple indents were conducted on the cross-section of the surface recast layer, sub-surface heat-affected zone, and bulk material. The energy disperse X-ray spectrometry and X-ray diffraction were used to analyze the material compositions in the heat-affected zone and recast layer and to study the electrical spark eroded surface. The indents were inspected by scanning electron microscopy to distinguish between regular and irregular indents in these three regions. Irregular indents were caused by the porosity, soft matrix material, separation of grain boundaries, and thermal cracks caused by EDM process. The hardness and modulus of elasticity obtained from regular indents in bulk material and heat-affected zone were comparable to those of WC. It was found that the recast layer had lower hardness and modulus of elasticity than the bulk material and heat-affected zone. DA - 2003/3/15/ PY - 2003/3/15/ DO - 10.1016/s0921-5093(02)00395-7 VL - 344 IS - 1-2 SP - 125-131 SN - 0921-5093 KW - nanoindentation KW - mechanical properties KW - metal matrix ceramic composites KW - electrical discharge machining ER - TY - JOUR TI - Mechanical properties of polyphenylene-sulfide (PPS) bonded NdFe-B permanent magnets AU - Garrell, MG AU - Ma, BM AU - Shih, AJ AU - Lara-Curzio, E AU - Scattergood, RO T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Mechanical properties, namely tensile and flexural strengths and elastic modulus, of polyphenylene-sulfide (PPS) bonded Nd–Fe–B magnets have been studied from −40 to 180 °C. The ultimate tensile strength (Sut) of PPS bonded magnets decreases with increasing temperature. The tensile strength of PPS bonded Nd–Fe–B magnets was reduced significantly above 100 °C. At 180 °C, the PPS bonded magnets still exhibit a Sut of 16–18 MPa. For bonded magnets with about 60% volume fraction of Nd–Fe–B powder, the PPS bonded magnet shows about twice the tensile strength and half the ultimate strain compared to that of Nylon bonded magnet. At room temperature, the flexural strength is, in general, comparable to the tensile strength. Dynamic elastic modulus measured using the impact resonance method was in good agreement with the elastic modulus obtained from tensile tests. Scanning Electron Microscopy analyses of the fractured surfaces revealed two distinct failure mechanisms. Debonding along the Nd–Fe–B particle and PPS interface is the main cause for failures at 100 and 180 °C. The fracture of Nd–Fe–B particle was observed on the fracture surface of specimens tested at −40 and 23 °C. DA - 2003/10/25/ PY - 2003/10/25/ DO - 10.1016/s0921-5093(03)00400-3 VL - 359 IS - 1-2 SP - 375-383 SN - 0921-5093 KW - polyphenylene-sulfide bonded magnets KW - tensile strength KW - flexural strength KW - elastic modulus ER - TY - JOUR TI - High-pressure phase transformation of silicon nitride AU - Patten, J AU - Fesperman, R AU - Kumar, S AU - McSpadden, S AU - Qu, J AU - Lance, M AU - Nemanich, R AU - Huening, J T2 - APPLIED PHYSICS LETTERS AB - We provide evidence for a high-pressure phase transformation (HPPT) in the ceramic material silicon nitride. This HPPT is inferred by a high-pressure diamond anvil cell, Raman spectroscopy, scanning/transmission electron microscopy, and optical and acoustic microscope inspection. In the case of silicon nitride, the HPPT involves a ductile or metallike behavior that is observed in severe deformation processes, such as nanoindentation and micromachining. This pressure-induced plasticity is believed to be similar to that found in silicon and germanium with its origin in the high-pressure metallic β-Sn phase formation. DA - 2003/12/8/ PY - 2003/12/8/ DO - 10.1063/1.1632031 VL - 83 IS - 23 SP - 4740-4742 SN - 0003-6951 ER - TY - JOUR TI - Gallium nitride and related materials: challenges in materials processing AU - Davis, RF AU - Einfeldt, S AU - Preble, EA AU - Roskowski, AM AU - Reitmeier, ZJ AU - Miraglia, PQ T2 - ACTA MATERIALIA AB - Boules and large wafers of the III-Nitrides of AlN, GaN and InN having a low density of dislocations are not available. As such, essentially all nitride films and device structures are grown on either sapphire or silicon carbide substrates containing a previously deposited buffer layer of GaN, AlN or AlGaN. These films grow via complex thermodynamically- and kinetically-controlled mechanisms and contain significant residual stresses and densities of defects that affect the properties of all optoelectronic and microelectronic devices produced in this materials system. It is the purpose of this paper to describe the challenges presented by the growth of these heteroepitaxial films and some of the recent results of research to understand the complex relationships between film growth, and stress and defect generation as well as the reduction in these mechanical and microstructural problems. Films of GaN grow on AlN/SiC substrates via the formation of a 1–1.5 nm thick wetting layer and the subsequent growth and coalescence of islands. These films are biaxially stressed. Increasing their thickness causes a gradual change in their average strain and their local strain from compression to tension due to the mismatch in lattice parameters between GaN and AlN and the mismatch in the coefficients of thermal expansion between GaN and SiC. A portion of the compressive stress is relieved within the first 20 nm due to the formation of misfit dislocations. Copious threading dislocations are also generated. Additional microstructural problems are presented by the SiC substrates that contain domains with varying size and tilt that are mimicked in the GaN films and that mask most variations in the FWHM of their X-ray rocking curves. Reduction in both the residual stresses and the dislocation density has been achieved via lateral overgrowth techniques. DA - 2003/11/25/ PY - 2003/11/25/ DO - 10.1016/j.actamat.2003.08.005 VL - 51 IS - 19 SP - 5961-5979 SN - 1873-2453 KW - compound semiconductors KW - thin films KW - dislocations KW - strain KW - pendeo-epitaxy ER - TY - JOUR TI - Evolution of microstructure and mechanical properties of in situ consolidated bulk ultra-fine-grained and nanocrystalline Zn prepared by ball milling AU - Zhang, X AU - Wang, H AU - Scattergood, RO AU - Narayan, J AU - Koch, CC T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - The evolution of the microstructure and mechanical properties of ultra-fine-grained and nanocrystalline Zn induced by ball milling at room temperature are studied systematically. The yield stresses measured from miniaturized disk bend tests and tensile tests are consistent with the microhardness results and generally increase with the decrease of average grain size. A dramatic decrease of hardness during milling from 1 to 3 h is a reflection of the increase of average grain size from 80 to 240 nm due to the initial unstable grain size and therefore, grain growth in this period. Young's modulus remains almost the same for samples milled for different times and is that for conventional grain size Zn. A transition from bending to membrane stretching is observed in the force–displacement curves for Zn ball milled for ≤18 h. The variation of transition strain with milling time could be related to the evolution of grain size distribution and therefore hardness during milling. DA - 2003/3/15/ PY - 2003/3/15/ DO - 10.1016/s0921-5093(02)00422-7 VL - 344 IS - 1-2 SP - 175-181 SN - 0921-5093 KW - ultra-fine-grain KW - nanocrystalline KW - force-displacement ER - TY - JOUR TI - Diffusion-accomodated rigid-body translations along grain boundaries in nanostructured materials AU - Bachurin, DV AU - Nazarov, AA AU - Shenderova, OA AU - Brenner, DW T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - A model for the structural relaxation of grain boundaries (GBs) in nanostructured materials (NSMs) by diffusion-accommodated rigid body translations along GBs is proposed. The model is based on the results of recent computer simulations that have demonstrated that the GBs in NSMs retain a high-energy structure with random translational states due to severe geometrical constraints applied from neighboring grains (J. Appl. Phys. 78 (1995) 847; Scripta Metall. Mater. 33 (1995) 1245). The shear stresses within a GB caused by non-optimized rigid-body translations (RBTs) can be accommodated by diffusive flow of atoms along a GB. This mechanism is particularly important for low-angle and vicinal GBs, the energy of which noticeably depends on the rigid body translations. At moderate and high temperatures the model yields relaxation times that are very short and therefore GBs in NSMs can attain an equilibrium structure with optimized rigid body translations. In contrast, at room temperature the model predicts that in some metals non-equilibrium structures can be preserved for a long time, which may result in the observation of grain boundary structures different from those in coarse grained polycrystals. DA - 2003/10/25/ PY - 2003/10/25/ DO - 10.1016/s0921-5093(03)00354-x VL - 359 IS - 1-2 SP - 247-252 SN - 1873-4936 KW - grain boundary KW - nanocrystalline materials KW - grain boundary diffusion ER - TY - JOUR TI - Dielectric functions of Cd1-xMgxTe alloy films by uusing spectroscopic ellipsometry AU - Ihn, Y. S. AU - Kim, T. J. AU - Kim, Y. D. AU - Aspnes, D. E. AU - Kossut, J. T2 - Journal of the Korean Physical Society DA - 2003/// PY - 2003/// VL - 43 IS - 4 SP - 634-637 ER - TY - JOUR TI - Cost-effective grinding of zirconia using the dense vitreous bond silicon carbide wheel AU - Shih, AJ AU - Scattergood, RO AU - Curry, AC AU - Yonushonis, TM AU - Gust, DJ AU - Grant, MB AU - McSpadden, SB AU - Watkins, TR T2 - JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME AB - Results of grinding zirconia using wheels with fine grain size SiC and dense vitreous bond are presented. Wheel wear results demonstrated that this type of SiC wheel could grind fully and partially stabilized zirconia (PSZ) very effectively. X-ray diffraction was used to analyze the percentage of monoclinic phase in the PSZ base material, ground surface, and debris. As expected, due to the stress- and temperature-induced phase transformation during grinding, the percentage of monoclinic phase on the ground surface was increased relative to the base material. However, X-ray diffraction showed no monoclinic phase in the PSZ debris. This suggests that, during grinding, the low thermal conductivity of zirconia and SiC, compared to that of diamond, facilitates heat retention in the chip and softens the work-material. This makes the efficient grinding of PSZ possible. Grinding temperature measurement results supported this hypothesis. DA - 2003/5// PY - 2003/5// DO - 10.1115/1.1559167 VL - 125 IS - 2 SP - 297-303 SN - 1087-1357 ER - TY - JOUR TI - Characterization of hydrogen etched 6H-SiC(0001) substrates and subsequently grown AlN films AU - Hartman, JD AU - Roskowski, AM AU - Reitmeier, ZJ AU - Tracy, KM AU - Davis, RF AU - Nemanich, RJ T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Wafers of n-type, 6H–SiC(0001) with (ND–NA)=(5.1–7.5)×1017 and 2.5×1018 were etched in a flowing 25%H2/75%He mixture within the range of 1500–1640 °C at 1 atm. Equilibrium thermodynamic calculations indicated that the presence of atomic hydrogen is necessary to achieve etching of SiC. Atomic force microscopy, optical microscopy, and low energy electron diffraction of the etched surface revealed a faceted surface morphology with unit cell and half unit cell high steps and a 1×1 reconstruction. The latter sample also exhibited a much larger number of hexagonal pits on the surface. Annealing the etched samples under ultrahigh vacuum (UHV) at 1030 °C for 15 min resulted in (1) a reduction of the surface oxygen and adventitious hydrocarbons below the detection limit of Auger electron spectroscopy, (2) a (√3×√3)R30° reconstructed surface and (3) a Si-to-C peak-to-peak height ratio of 1.2. By contrast, using a chemical vapor cleaning (CVC) process consisting of an exposure to 3000 Langmuir (L) of silane at 1030 °C for 10 min under UHV conditions resulted in a (3×3) surface reconstruction, a Si-to-C ratio of 3.9, and islands of excess silicon. Continued annealing of the latter material for an additional 10 min at 1030 °C resulted in a (1×1) LEED pattern with a diffuse ring. Films of AlN grown via MOCVD at a sample platter temperature of 1274 °C for 15 min on hydrogen etched wafers having a doping concentration of 8.7×1017 cm−3 and cleaned via annealing had a rms roughness value of ≈0.4 nm. DA - 2003/// PY - 2003/// DO - 10.1116/1.1539080 VL - 21 IS - 2 SP - 394-400 SN - 0734-2101 ER - TY - JOUR TI - Structure, energetics, and thermal stability of nitrogen-vacancy-related defects in nitrogen doped silicon AU - Karoui, A AU - Karoui, FS AU - Rozgonyi, GA AU - Hourai, M AU - Sueoka, K T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - The electronic structure, formation energy, and thermal stability of nitrogen-vacancy related complexes in silicon have been investigated using density functional theory and semi-empirical Hartree-Fock calculations. The calculated energies of formation in the ground state showed that was not stable, whereas when formed from was the most stable, followed by and formed from a divacancy. The calculated free energy changes of the considered chemical reactions confirmed the low stability of compared to The latter can form during crystal growth from whereas reactions between and divacancy can also occur upon wafer heating. At low nitrogen concentration cm−3), only about 10% of vacancy concentration was converted into while at a high nitrogen concentration cm−3) about 75% of vacancies are trapped by nitrogen. appeared to create a potential well of −2.4 eV for oxygen and about −0.3 eV for vacancies, suggesting that the stable is a nucleus for oxygen precipitation while it is a weak trapping center for vacancies. © 2003 The Electrochemical Society. All rights reserved. DA - 2003/12// PY - 2003/12// DO - 10.1149/1.1621418 VL - 150 IS - 12 SP - G771-G777 SN - 1945-7111 ER - TY - JOUR TI - Semiclassical calculation of reaction rate constants for homolytical dissociation reactions of interest in organometallic vapor-phase epitaxy (OMVPE) AU - Cardelino, BH AU - Moore, CE AU - Cardelino, CA AU - McCall, SD AU - Frazier, DO AU - Bachmann, KJ T2 - JOURNAL OF PHYSICAL CHEMISTRY A AB - A procedure for calculating homolytic dissociation rate constants is reported for modeling organometallic vapor-phase epitaxy (OMVPE) of III−V compounds for all pressure regimes. Reaction rate constants were predicted following a semiclassical approach based on quantum mechanical calculations and transition-state theory. The critical configuration was determined using linear interpolations for the geometry of the intermediate structures, Morse potentials for the intermediate electronic energies, and Hase's relationship for the vibrational frequencies that become annihilated. Low-pressure rate constants were calculated from Rice−Ramsperger−Kassel−Marcus (RRKM) theory following the Troe approach. The calculations were compared with experimental values for the dissociation of one methyl radical from the closed-shell molecules Al(CH3)3, Ga(CH3)3, and In(CH3)3 and the radical molecules Ga(CH3)2 and In(CH3) and for the dissociation of one hydrogen atom from NH3, PH3, and AsH3. A simplified system of reactions for the homolytic dissociation of In(CH3)3 was modeled in an OMV reactor designed for the pressure range 10-2 to 102 atm using computational fluid dynamics coupled with chemical kinetics. The steady-state simulations were carried out at 1000 K and at N2 pressures of 1 and 20 atm. DA - 2003/5/15/ PY - 2003/5/15/ DO - 10.1021/jp026289j VL - 107 IS - 19 SP - 3708-3718 SN - 1089-5639 ER - TY - JOUR TI - R&D of diamond films in the Frontier Carbon Technology Project and related topics AU - Kobashi, K AU - Nishibayashi, Y AU - Yokota, Y AU - Ando, Y AU - Tachibana, T AU - Kawakami, N AU - Hayashi, K AU - Inoue, K AU - Meguro, K AU - Imai, H AU - Furata, H AU - Hirao, T AU - Oura, K AU - Gotoh, Y AU - Nakahara, H AU - Tsuji, H AU - Ishikawa, J AU - Koeck, FA AU - Nernanich, RJ AU - Sakai, T AU - Sakuma, N AU - Yoshida, H T2 - DIAMOND AND RELATED MATERIALS AB - R&D activities on diamond chemical vapor deposition (CVD) and field emission in the Frontier Carbon Technology Project are presented. The topics are (1) morphology control of diamond films grown by a 60-kW, 915-MHz microwave plasma CVD reactor, (2) growth technology of large single crystal diamond with a low density of defects, (3) heteroepitaxial growth technology of diamond films on Pt, (4) fabrication of sharp emitter tips on single crystal diamond, (5) field emission study from diamond particles, and (6) intense field emission from ion implanted homoepitaxial diamond layer. Research results of field emission obtained by Kyoto University and North Carolina State University are also described. DA - 2003/// PY - 2003/// DO - 10.1016/S0925-9635(02)00298-4 VL - 12 IS - 3-7 SP - 233-240 SN - 1879-0062 KW - diamond films KW - chemical vapor deposition KW - etching KW - field emission ER - TY - JOUR TI - Processing routes for direct bonding of silicon to epitaxially textured diamond AU - Wolter, SD AU - Yushin, GN AU - Prater, JT AU - Sitar, Z T2 - DIAMOND AND RELATED MATERIALS AB - Direct bonding of (1 0 0) silicon to epitaxially textured diamond is reported. Fusion of the silicon wafers to the diamond specimens was conducted at high temperature, under an applied stress of 32 MPa in a dedicated ultra-high vacuum bonding apparatus. The highly oriented films were characterized by a RMS surface roughness of ∼150.0 nm (via atomic force microscopy) and discrete crystallites that had formed on the otherwise smooth, (1 0 0)-sheet textured surfaces. Consequently, only partial bonding was observed from 950 to 1150 °C; attempts at silicon-to-diamond fusion at lower temperatures were unsuccessful. The diamond films were also mechanically polished to a RMS surface roughness of ∼5.0 nm. Successful bonding of silicon to these films was observed at fusion temperatures ⩾850 °C using the same processing conditions implemented in the unpolished diamond work. Scanning acoustic microscopy revealed a more uniform interface in these silicon-on-diamond specimens. DA - 2003/// PY - 2003/// DO - 10.1016/S0925-9635(02)00392-8 VL - 12 IS - 3-7 SP - 257-261 SN - 0925-9635 KW - wafer bonding KW - silicon-on-diamond KW - silicon-on-insulator ER - TY - JOUR TI - Planar gallium nitride ultraviolet optical modulator AU - Oberhofer, AE AU - Muth, JF AU - Johnson, MAL AU - Chen, ZY AU - Fleet, EF AU - Cooper, GD T2 - APPLIED PHYSICS LETTERS AB - A planar optical modulator operating near 360 nm suitable for ultraviolet spatial light modulation has been constructed. The modulator operates in transmission mode with a 18% change in transmission at 305 V. The modulator is based on using the electric field to shift and broaden the room-temperature resonance of the gallium nitride exciton with electric fields. DA - 2003/10/6/ PY - 2003/10/6/ DO - 10.1063/1.1615675 VL - 83 IS - 14 SP - 2748-2750 SN - 0003-6951 ER - TY - JOUR TI - Origin and implications of the observed rhombohedral phase in nominally tetragonal Pb(Zr0.35Ti0.65)O-3 thin films AU - Kelman, MB AU - McIntyre, PC AU - Gruverman, A AU - Hendrix, BC AU - Bilodeau, SM AU - Roeder, JF T2 - JOURNAL OF APPLIED PHYSICS AB - The structural and electrical properties of Pb(Zr0.35Ti0.65)O3 (PZT) thin films ranging in thickness from 700 to 4000 Å have been investigated. These (001)/(100)-textured films were grown by metalorganic chemical vapor deposition on (111)-textured Ir bottom electrodes. It was observed that, in the as-deposited state, the thinnest PZT films are rhombohedral even though bulk PZT of this composition should be tetragonal. Thicker films have a layered structure with tetragonal PZT at the surface and rhombohedral PZT at the bottom electrode interface. In this article we investigate the origin of this structure and its effect of the ferroelectric and dielectric properties of PZT capacitors. It has been suggested that thin films stresses can affect the phase stability regions of single domain PZT. This possibility has been investigated by piezoresponse microscopy and thin film stress measurements. In the as-deposited state the majority of PZT grains contain a single ferroelastic domain, whereas after a high temperature anneal, a large fraction of the grains contain several ferroelastic domains. Wafer curvature measurements in combination with x-ray diffraction stress measurements in the Ir bottom electrode showed that the as-deposited PZT films are, within experimental error, stress free at room temperature. Landau–Ginbzurg–Devonshire formalism was used to explain the origin of the rhombohedral phase as a result of substrate constraint on single domain PZT grains. Annealing was found to affect the relative volume fractions of the rhombohedral and tetragonal phases and the electrical properties of PZT films. Intermediate temperature anneals increased the volume fraction of the rhombohedral phase and the coercive field extracted from the polarization-electric field hysteresis loops. After a high temperature anneal (650 °C) the majority of the grains transformed into a polydomain state, decreasing the volume fraction of the rhombohedral phase and the coercive field. If the high temperature anneal was performed after deposition of the top electrode, the coercive field became independent of the PZT thickness. DA - 2003/10/15/ PY - 2003/10/15/ DO - 10.1063/1.1610773 VL - 94 IS - 8 SP - 5210-5219 SN - 1089-7550 ER - TY - JOUR TI - Nanocomposite electrolytes with fumed silica and hectorite clay networks: Passive versus active fillers AU - Walls, HJ AU - Riley, MW AU - Singhal, RR AU - Spontak, RJ AU - Fedkiw, PS AU - Khan, SA T2 - ADVANCED FUNCTIONAL MATERIALS AB - Abstract The use of nanocomposites constitutes a versatile and robust approach in the development of novel electrolytes with tailored electrochemical and mechanical characteristics. In this study, we examine the morphology, rheology, and ion‐transport properties of two types of nanocomposite electrolyte gels, one consisting of branched silica nanoparticles and the other composed of hectorite clay. In the first system with hydrophobic (fumed) silica, oligomers of poly(ethylene oxide) (PEO), and lithium salt, the silica acts as a passive filler and does not participate in ion transport. The electrochemical properties are controlled by the salt–PEO electrolyte, allowing for ionic conductivities greater than 10 –3 S cm –1 at ambient temperature. At sufficiently high concentrations, the silica forms an elastic gel possessing a large open network structure that provides for unimpeded ion mobility. In the second system composed of lithium‐exchanged hectorite filler, the nanoscale platelets serve as the anion. This active filler yields ionic conductivities in excess of 10 –4 S cm –1 and lithium transference numbers approaching unity. Similar to fumed silica, the hectorite clay also forms an elastic gel network. However, the morphologies of the two systems are distinctively different both in terms of network structure and characteristic length scale. These morphological differences manifest themselves in different rheological responses with regard to gel modulus and yield stress. DA - 2003/9// PY - 2003/9// DO - 10.1002/adfm.200304333 VL - 13 IS - 9 SP - 710-717 SN - 1616-301X ER - TY - JOUR TI - In situ point defect generation and agglomeration during electron-beam irradiation of nitrogen-doped Czochralski silicon AU - Stoddard, N AU - Karoui, A AU - Duscher, G AU - Kvit, A AU - Rozgonyi, G T2 - ELECTROCHEMICAL AND SOLID STATE LETTERS AB - Samples of Czochralski silicon were observed after irradiation by a convergent electron beam in a transmission electron microscope. In a nitrogen-doped sample, the 200 keV electrons induced a vacancy-rich region containing point-defect clusters, surrounded by a ring rich in self-interstitials. No comparable effect existed in nitrogen-free reference samples. It is proposed that Frenkel pairs, created by electron collisions, are separated and stabilized by nitrogen or related complexes. Some interstitials become free to diffuse while the nitrogen, vacancies and oxygen agglomerate. This study demonstrates that the initial formation of voids and precipitate nuclei from point defects can be observed at low temperatures. © 2003 The Electrochemical Society. All rights reserved. DA - 2003/11// PY - 2003/11// DO - 10.1149/1.1614471 VL - 6 IS - 11 SP - G134-G136 SN - 1944-8775 ER - TY - JOUR TI - Helical-type surface defects in InGaN thin films epitaxially grown on GaN templates at reduced temperatures AU - Miraglia, PQ AU - Preble, EA AU - Roskowski, AM AU - Einfeldt, S AU - Lim, SH AU - Liliental-Weber, Z AU - Davis, RF T2 - THIN SOLID FILMS AB - Abstract The surface morphologies of InGaN films grown at 780 °C by metalorganic vapor phase epitaxy were determined using atomic force microscopy. A qualitative model was developed to explain the observed instabilities in the step morphology of these films, namely, the formation of hillocks and v-defects that give rise to surface roughening. V-defects, observed at a surface density greater than 2×10 8 /cm 2 , are a result of interactions between moving surface steps, cores of screw-type dislocations, and two-dimensional islands of atoms that form on the terraces during growth at high surface undercooling. A delay in the formation of v-defects in InGaN to a nominal thickness of 10 nm was observed and associated with the ammonia partial pressure and the interactions between steps associated with hillock islands and cores of screw-type dislocations. Hillock formation was attributed to a transition in the thermodynamic mode of film growth, as three-dimensional islands nucleated on the cores of screw-type dislocations at a density of 2×10 8 /cm 2 . Explanations for the foregoing observations are based on growth model theory previously developed by Burton, Cabrera and Frank and on changes in the surface kinetics with temperature, In composition, and gas phase composition. DA - 2003/8/1/ PY - 2003/8/1/ DO - 10.1016/S0040-6090(03)00611-4 VL - 437 IS - 1-2 SP - 140-149 SN - 1879-2731 KW - surface defects KW - atomic force microscopy KW - metalorganic vapor phase epitaxy KW - indium gallium nitride ER - TY - JOUR TI - Growth and characteristics of TaN/TiN superlattice structures AU - Wang, H AU - Zhang, X AU - Gupta, A AU - Tiwari, A AU - Narayan, J T2 - APPLIED PHYSICS LETTERS AB - Epitaxial B1 NaCl-structured TaN(3 nm)/TiN(2 nm) superlattice structures were grown on Si(100) substrates with a TiN buffer layer, using pulsed-laser deposition. A special target assembly was used to manipulate the thickness of each layer. X-ray diffraction, transmission electron microscopy, and scanning transmission electron microscopy (Z contrast) studies confirmed the single-crystalline nature of the superlattice with a uniform layer structure. Nanoindentation results suggest the high hardness of these superlattice structures. Four-point-probe resistivity measurements show low resistivity of the heterostructures and a Cu diffusion characteristic study proved this superlattice system can be a promising diffusion barrier and can withstand 700 °C annealing for 30 min. DA - 2003/10/13/ PY - 2003/10/13/ DO - 10.1063/1.1616656 VL - 83 IS - 15 SP - 3072-3074 SN - 0003-6951 ER - TY - JOUR TI - Formation of self-assembled epitaxial nickel nanostructures AU - Zhou, H AU - Kumar, D AU - Kvit, A AU - Tiwari, A AU - Narayan, J T2 - JOURNAL OF APPLIED PHYSICS AB - Highly orientated nickel magnetic nanoparticles were obtained by pulsed laser deposition technique on silicon (100) substrate using epitaxial titanium nitride film as the template. These nanoparticles have been characterized by conventional and high-resolution transmission electron microscopy, scanning transmission electron microscopy Z-contrast imaging, and x-ray diffraction techniques. The results have shown that the growth of nickel on epitaxially grown titanium nitride follows a three-dimensional island growth mechanism. The predominant orientation of nickel islands observed is Ni(100)∥TiN(100)∥Si(100), the so-called “cube-on-cube” orientation relation. The islands are faceted with a truncated pyramidal shape and bounded by (111) planes at sides and (100) plane at the top. Islands with nontruncated pyramidal shape were also found in some samples, but with rotational orientation relations, where the nickel crystal rotates with an approximate angle of 90° with respect to one of TiN 〈110〉 directions parallel to the interface. The appearance of this rotational epitaxial growth did not show any obvious deposition temperature dependence in the range of 400–650 °C, rather it seemed to be closely related to the crystalline quality of TiN template. The actual size of islands varies from a few nanometers to tens of nanometers, depending on the deposition time and temperature. The three-dimensional growth of nickel islands and the island faceting could be explained by the surface energy anisotropy of both nickel and titanium nitride. DA - 2003/10/15/ PY - 2003/10/15/ DO - 10.1063/1.1609046 VL - 94 IS - 8 SP - 4841-4846 SN - 1089-7550 ER - TY - JOUR TI - Electrical and chemical characterization of the Schottky barrier formed between clean n-GaN(0001) surfaces and Pt, Au, and Ag AU - Tracy, KM AU - Hartlieb, PJ AU - Einfeldt, S AU - Davis, RF AU - Hurt, EH AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - Platinum, gold, and silver formed abrupt, unreacted, smooth, and epitaxial metal–semiconductor interfaces when deposited from the vapor onto clean, n-type GaN(0001) films. The Schottky barrier heights, determined from data acquired using x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, capacitance–voltage, and current–voltage measurements agreed to within the experimental error for each contact metal and had the values of 1.2±0.1, 0.9±0.1, and 0.6±0.1 eV for Pt, Au, and Ag, respectively. The band bending and the electron affinity at the clean n-GaN surface were 0.3±0.1 and 3.1±0.1 eV, respectively. The barrier height is proportional to the metal work function, indicating that the Fermi level is not pinned at the GaN surface. However, discrepancies to the Schottky–Mott model were found as evidenced by a proportionality factor of 0.44 between the work function of the metal and the resulting Schottky barrier height. The sum of these discrepancies constitute the interface dipole contributions to the Schottky barrier height which were measured to be ∼1.4, 1.3, and 0.7 eV for Pt, Au, and Ag, respectively. DA - 2003/9/15/ PY - 2003/9/15/ DO - 10.1063/1.1598630 VL - 94 IS - 6 SP - 3939-3948 SN - 0021-8979 ER - TY - JOUR TI - Effects of composition and matrix polarity on network development in organogels of poly(ethylene glycol) and dibenzylidene sorbitol AU - Wilder, EA AU - Hall, CK AU - Khan, SA AU - Spontak, RJ T2 - LANGMUIR AB - Dibenzylidene sorbitol (DBS) is a low-molecular-weight organic molecule that can gel a variety of organic solvents and polymers by self-organizing into a three-dimensional nanofibrillar network through hydrogen-bonding and phenyl interactions. In this work, we investigate the composition dependence of such “organogels” prepared with poly(ethylene glycol) (PEG) and two PEG derivatives differing in methoxy end- group substitution, which serves to reduce matrix polarity. Transmission electron microscopy reveals that individual DBS nanofibrils measure from about 10 to 70 nm in diameter, with a primary nanofibrillar diameter of about 10 nm. Dynamic rheological measurements indicate that the rate by which the elastic modulus increases during gelation, the temperatures corresponding to gel formation and dissolution, and the magnitude of the elastic modulus are all sensitive to the DBS mass concentration (φ) and the matrix polarity. Hydroxy-end-capped PEG/DBS systems gel more slowly, but dissolve faster, than their methoxy-end-capped analogues at constant φ. The elastic modulus, however, is less dependent on matrix polarity and scales as φ1.8 over the range of φ examined in PEG/DBS organogels. Time−temperature superposition analysis provides direct evidence for the activation energy of network evolution increasing linearly with (i) decreasing φ at constant matrix polarity and (ii) increasing matrix polarity at constant φ. DA - 2003/7/22/ PY - 2003/7/22/ DO - 10.1021/la027081s VL - 19 IS - 15 SP - 6004-6013 SN - 0743-7463 ER - TY - JOUR TI - Effect of the composition on the electrical properties of TaSixNy metal gate electrodes AU - Suh, YS AU - Heuss, GP AU - Lee, JH AU - Misra, V T2 - IEEE ELECTRON DEVICE LETTERS AB - In this letter, the effect of silicon and nitrogen on the electrical properties of TaSi/sub x/N/sub y/ gate electrode were investigated. The TaSi/sub x/N/sub y/ films were deposited on SiO/sub 2/ using reactive cosputtering of Ta and Si target in Ar and N/sub 2/ ambient. The thermal stability of TaSi/sub x/N/sub y//SiO/sub 2//p-type Si stacks was evaluated by measuring the flatband voltage and equivalent oxide thickness at 400/spl deg/C and 900/spl deg/C in Ar. It was found that under high temperature anneals, Si-rich TaSi/sub x/N/sub y/ films increased and this was attributed to the formation of a reaction layer at the electrode-dielectric interface. Reducing the Si content alone did not prevent the formation of this reaction layer while removing Si completely by utilizing TaN resulted in work functions that were too high. The presence of both Si and N was deemed necessary and their content was critical in obtaining optimized TaSi/sub x/N/sub y/ gates that are suitable for NMOS devices. DA - 2003/7// PY - 2003/7// DO - 10.1109/LED.2003.814009 VL - 24 IS - 7 SP - 439-441 SN - 1558-0563 KW - dual metal gates KW - gate Electrodes KW - low work function KW - MOS capacitors KW - N diffusion KW - TaSiN ER - TY - JOUR TI - Dielectric functions of InxGa1-xAs alloys AU - Kim, TJ AU - Ghong, TH AU - Kim, YD AU - Kim, SJ AU - Aspnes, DE AU - Mori, T AU - Yao, T AU - Koo, BH T2 - PHYSICAL REVIEW B AB - We present room-temperature pseudodielectric function spectra $〈\ensuremath{\varepsilon}〉=〈{\ensuremath{\varepsilon}}_{1}〉+i〈{\ensuremath{\varepsilon}}_{2}〉$ of ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ films grown on (100) InP by solid-source molecular-beam epitaxy. A wet-chemical etching procedure was used to remove overlayers and obtain the best approximation to the bulk dielectric responses $\ensuremath{\varepsilon}={\ensuremath{\varepsilon}}_{1}+i{\ensuremath{\varepsilon}}_{2}$ of the films. By lineshape fitting we determined the dependences of the ${E}_{1}{,E}_{1}+{\ensuremath{\Delta}}_{1}{,E}_{0}^{\ensuremath{'}}{,E}_{0}^{\ensuremath{'}}+{\ensuremath{\Delta}}_{0}^{\ensuremath{'}},$ and ${E}_{2}$ critical-point energies on x. Using a parametric semiconductor model we represent these spectra analytically to allow $〈\ensuremath{\varepsilon}〉$ to be calculated as a continuous function of x. These results are expected to be useful for design purposes, for example of nanostructures and multilayer systems involving ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}.$ DA - 2003/9/15/ PY - 2003/9/15/ DO - 10.1103/physrevb.68.115323 VL - 68 IS - 11 SP - SN - 1098-0121 ER - TY - JOUR TI - American Vacuum Society leadership in electronic materials processing: Past, present, and future AU - Lucovsky, G AU - Rubloff, G T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - This article traces the evolution of electronics materials processing in the American Vacuum Society (AVS) up to the present time, and projects the trajectory of this activity into the future. The format and style of this article benefits from perspective of one of the authors (G.L.), who has been editor-in-chief of the Journal of Vacuum Science and Technology (JVST) for more than 20 years, and who has additionally contributed personally to materials processing research through interactions involving AVS symposia, divisions, and publications in the JVST. Major areas of contributions are identified, and then are correlated with the evolution of the AVS and JVST. As we move into the 21st century, the foundation laid by a strong presence in electronic materials processing is proving to be the basis for emerging cross-disciplinary AVS activities in the nanoscience and technology advances that will continue to evolve in unanticipated ways in 21st century and beyond. DA - 2003/// PY - 2003/// DO - 10.1116/1.1599866 VL - 21 IS - 5 SP - S175-S181 SN - 1520-8559 ER - TY - JOUR TI - Synthesis of bulk nanostructured Zn by combinations of cryomilling and powder consolidation by room temperature milling: optimizing mechanical properties AU - Zhu, XK AU - Zhang, X AU - Wang, H AU - Sergueeva, AV AU - Mukherjee, AK AU - Scattergood, RO AU - Narayan, J AU - Koch, CC T2 - SCRIPTA MATERIALIA AB - A new technique is used to synthesize nanocrystalline Zn, i.e. cryomilling followed by in situ consolidation of the powders by room temperature ball milling. The room temperature milling appears to sharpen the broad grain size distribution obtained by cryomilling only. Strength and ductility may be optimized in this way by the control of grain size and grain size distribution. DA - 2003/9// PY - 2003/9// DO - 10.1016/S1359-6462(03)00297-5 VL - 49 IS - 5 SP - 429-433 SN - 1359-6462 KW - mechanical milling KW - nanocrystalline KW - tension test ER - TY - JOUR TI - Remote plasma-assisted nitridation (RPN): applications to Zr and Hf silicate alloys and Al2O3 AU - Hinkle, C AU - Lucovsky, G T2 - APPLIED SURFACE SCIENCE AB - Remote plasma-assisted nitridation or RPN is demonstrated to be a processing pathway for nitridation of Zr and Hf silicate alloys, and for Al2O3, as well. The dependence of nitrogen incorporation on the process pressure is qualitatively similar to what has been reported for the plasma-assisted nitridation of SiO2, the lower the process pressure the greater the nitrogen incorporation in the film. The increased incorporation of nitrogen has been correlated with the penetration of the plasma-glow into the process chamber, and the accompanying increase in the concentration of N2+ ions that participate in the reactions leading to bulk incorporation. The nitrogen incorporation as been studied by Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS) and X-ray absorption spectroscopy (XAS). DA - 2003/6/30/ PY - 2003/6/30/ DO - 10.1016/S0169-4332(03)00499-9 VL - 216 IS - 1-4 SP - 124-132 SN - 0169-4332 KW - remote plasma nitridation KW - Auger electron spectroscopy KW - X-ray photoelectron spectroscopy KW - X-ray absorption spectroscopy KW - zirconium and hafnium silicate alloys KW - Al2O3 ER - TY - JOUR TI - Oxide formation and passivation for micro- and nano-electronic devices AU - Bae, C AU - Lucovsky, G T2 - APPLIED SURFACE SCIENCE AB - A low-temperature remote plasma-assisted oxidation process for interface formation and passivation has been extended from Si and SiC to GaN. The process, which can be applied to nano-scale structures including quantum dots and wires, provides excellent control of ultra-thin interfacial layers which passivate the GaN substrate, preventing a parasitic or subcutaneous oxidation of the substrate during plasma deposition of SiO2. The remote plasma processing for GaN–SiO2 heterostructures includes: (i) an in situ nitrogen plasma surface clean; (ii) a remote plasma-assisted oxidation for formation of an interfacial GaOx (x=1.5) transition region between the GaN and deposited dielectric; and (iii) a remote plasma-enhanced chemical vapor deposition of an SiO2 dielectric. DA - 2003/5/15/ PY - 2003/5/15/ DO - 10.1016/S0169-4332(03)00139-9 VL - 212 SP - 644-648 SN - 0169-4332 KW - plasma processing KW - Auger electron spectroscopy KW - semiconductor-insulator interfaces KW - interface states ER - TY - JOUR TI - Nano-scale analysis of precipitates in nitrogen-doped Czochralski silicon AU - Rozgonyi, GA AU - Karoui, A AU - Kvit, A AU - Duscher, G T2 - MICROELECTRONIC ENGINEERING AB - Nitrogen-doped Czochralski (CZ) silicon wafers were heat treated with Lo-Hi annealing in argon. Nanoscale defects were then examined by high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) in the Z-contrast mode, and electron energy loss spectroscopy (EELS) analyses using a field emission JEOL 2010 with a resolution below 2 A. The structures of precipitates, stacking faults and interstitial aggregates were found to depend on their location relative to the wafer surface. Precipitate composition, strain at the interface and interface roughness were obtained and are discussed in connection with the point defects generated during crystal growth and modified during wafer annealing. An excellent correlation was found between Z-contrast line scans across the precipitates and the N to O concentration ratio determined with EELS. In the precipitate central region that ratio is between 1 and 6%, whereas at precipitate boundaries it reaches 17%. DA - 2003/4// PY - 2003/4// DO - 10.1016/S0167-9317(02)00923-1 VL - 66 IS - 1-4 SP - 305-313 SN - 1873-5568 KW - Czochralski silicon wafers KW - nitrogen doping ER - TY - JOUR TI - Mechanical stress effect on imprint behavior of integrated ferroelectric capacitors AU - Gruverman, A AU - Rodriguez, BJ AU - Kingon, AI AU - Nemanich, RJ AU - Tagantsev, AK AU - Cross, JS AU - Tsukada, M T2 - APPLIED PHYSICS LETTERS AB - Stress-induced changes in the imprint and switching behavior of (111)-oriented Pb(Zr,Ti)O3 (PZT)-based capacitors have been studied using piezoresponse force microscopy. Visualization of polarization distribution and d33-loop measurements in individual 1×1.5-μm2 capacitors before and after stress application, generated by substrate bending, provided direct experimental evidence of stress-induced switching. Mechanical stress caused elastic switching in capacitors with the direction of the resulting polarization determined by the sign of the applied stress. In addition, stress application turned capacitors into a heavily imprinted state characterized by strongly shifted hysteresis loops and almost complete backswitching after application of the poling voltage. It is suggested that substrate bending generated a strain gradient in the PZT layer, which produced asymmetric lattice distortion with preferential polarization direction and triggered polarization switching due to the flexoelectric effect. DA - 2003/7/28/ PY - 2003/7/28/ DO - 10.1063/1.1593830 VL - 83 IS - 4 SP - 728-730 SN - 0003-6951 ER - TY - JOUR TI - GaN evaporation and enhanced diffusion of Ar during high-temperature ion implantation AU - Usov, I AU - Parikh, N AU - Kudriavtsev, Y AU - Asomoza, R AU - Reitmeier, Z AU - Davis, R T2 - JOURNAL OF APPLIED PHYSICS AB - GaN films were implanted with 150 keV Ar+ at temperatures up to 1100 °C to a dose of 3×1015 cm−2. Concentration profiles of Ar were measured by secondary ion mass spectroscopy and depth distributions of ion-induced damage were estimated from Rutherford backscattering/channeling spectra. No redistribution of Ar atoms was detected up to 700 °C. At 1000 °C a deep penetrating diffusion tail and a shift of the Ar peak to the surface were observed. At temperatures higher than 800 °C shift of the damage peak to the surface was also observed. We attributed the shift of the Ar peak and the damage peaks to evaporation of thin layer of GaN during high-temperature implantation and estimated its temperature dependence. DA - 2003/5/1/ PY - 2003/5/1/ DO - 10.1063/1.1564271 VL - 93 IS - 9 SP - 5140-5142 SN - 1089-7550 ER - TY - JOUR TI - Evolution and growth of ZnO thin films on GaN(0001) epilayers via metalorganic vapor phase epitaxy AU - Smith, TP AU - Mecouch, WJ AU - Miraglia, PQ AU - Roskowski, AM AU - Hartlieb, PJ AU - Davis, RF T2 - JOURNAL OF CRYSTAL GROWTH AB - Zinc oxide thin films have been grown via metalorganic vapor phase epitaxy at 450°C and 250 Torr total pressure on O-terminated areas and micro-regions of native oxide formed on GaN(0 0 0 1) epilayers during exposure to the oxygen reactant. Analyses of the Ga3d core level spectra acquired from films grown for progressively longer times and comparisons of these data with both thermodynamic models of growth processes and associated atomic force micrographs revealed that the ZnO nucleated and grew via the Stranski–Krastanov mode. Considerations of (1) differences in surface energetics of the polar (0 0 0 1) surfaces of ZnO and GaN and that of the Ga-based oxide as well as (2) the relatively low stress generated by the moderate lattice mismatches in the a-axis lattice parameters of these compounds supported the observed growth mode. The shifts in the position of the Ga3d core level with increasing deposition time and decreasing peak intensity were caused by surface charging and increasing sampling volumes of the Ga-based oxide as well as the growing ZnO layer. The island/ocean morphology of the Ga-based oxide controlled the morphology of the initial ZnO layer, which, in turn controlled the locations and the morphologies of the subsequently nucleated ZnO islands. Scanning electron microscopy of thicker ZnO films revealed a highly textured microstructure. DA - 2003/10// PY - 2003/10// DO - 10.1016/S0022-0248(03)01469-6 VL - 257 IS - 3-4 SP - 255-262 SN - 1873-5002 KW - crystal morphology KW - dislocations KW - stacking faults KW - x-ray diffraction KW - organometallic vapor phase deposition KW - ZnO ER - TY - JOUR TI - Evaluation of intrinsic and extrinsic contributions to the piezoelectric properties of Pb(Zr1-xTX)O-3 thin films as a function of composition AU - Kim, DJ AU - Maria, JP AU - Kingon, AI AU - Streiffer, SK T2 - JOURNAL OF APPLIED PHYSICS AB - The piezoelectric, dielectric, and ferroelectric properties of highly (111)-textured, 200-nm-thick polycrystalline lead zirconate titanate (PZT) films have been investigated as a function of Zr/Ti ratio. The distinct peak in piezoelectric coefficient at the morphotropic phase boundary found in bulk PZT ceramics is not observed in thin film PZTs. Measurements of the temperature dependence of relative permittivity and the nonlinear behavior of relative permittivity and piezoelectric coefficient suggest that non-180° domain wall motion in these films is negligible, indicating that the extrinsic contribution to the room temperature permittivity is dominated by only 180° domain wall motion. The semiempirical phenomenological equation relating the piezoelectric coefficient to measured polarization and permittivity values is demonstrated to give an excellent description of the piezoelectric behavior in these films, assuming bulk electrostrictive and elastic coefficients. The small deviation between calculated and measured piezoelectric coefficients as well as the dependence of piezoelectric and polarization behavior on the external field, i.e., hysteresis loop, are suggested to be primarily due to backswitching of 180° domains. DA - 2003/5/1/ PY - 2003/5/1/ DO - 10.1063/1.1566478 VL - 93 IS - 9 SP - 5568-5575 SN - 0021-8979 ER - TY - JOUR TI - Etching characteristics of chromium thin films by an electron beam induced surface reaction AU - Wang, JH AU - Griffis, DP AU - Garcia, R AU - Russell, PE T2 - SEMICONDUCTOR SCIENCE AND TECHNOLOGY AB - In this paper, we demonstrate the etching of chromium (Cr) film on quartz through a surface reaction induced by an electron beam and enhanced with XeF2 gas. We have studied the influences of the electron beam energy, the gas flow rate and the specimen composition on the etch rate. The electron beam energy has significant influence on the etch rate. The etch rate made by an electron beam of 20 keV is five times higher compared to that made by a beam of 10 keV. The XeF2 gas flow rate shows little effect on the etch rate when the gas pressure is higher than 2 × 10−6 Torr. The structure and grain size of the Cr film did not show any apparent change under exposure to XeF2 or when irradiated by an electron beam, while the composition of Cr has a significant effect on the etch process. The material removal of Cr induced by an electron beam means that it can be applied to the direct fabrication of microstructures on Cr films and that it solves the contamination problem in Cr mask repair. DA - 2003/4// PY - 2003/4// DO - 10.1088/0268-1242/18/4/302 VL - 18 IS - 4 SP - 199-205 SN - 0268-1242 ER - TY - JOUR TI - Electronic structure of transition metal/rare earth alternative high-K gate dielectrics: interfacial band alignments and intrinsic defects AU - Lucovsky, G T2 - MICROELECTRONICS RELIABILITY AB - Hybrid inorganic–organic solar cells typically combine a transition metal oxide and organic absorber to form the donor–acceptor pair. Here, we explore the use of a rare earth oxide to function as the inorganic component of a hybrid solar cell. Oxidized neodymium (Nd2O3) particles are combined with [6,6]-phenyl C61 butyric acid methyl ester (PCBM) to form the solar cell active layer. The short circuit current and open circuit voltage are both enhanced compared to pure PCBM. In addition, the photoinduced absorption decay rate increases, and photobleaching is observed. This provides evidence for charge transfer between the organic and rare earth inorganic components. DA - 2003/// PY - 2003/// DO - 10.1016/S0026-2714(03)00253-1 VL - 43 IS - 9-11 SP - 1417-1426 SN - 0026-2714 ER - TY - JOUR TI - Electronic structure of transition metal high-k dielectrics: interfacial band offset energies for microelectronic devices AU - Lucovsky, G AU - Raynor, GB AU - Zhang, Y AU - Fulton, CC AU - Nemanich, RJ AU - Appel, G AU - Ade, H AU - Whitten, JL T2 - APPLIED SURFACE SCIENCE AB - Transition metal silicates, (ZrO2)x(SiO2)1� x, have dielectric constants k > 10 that make them attractive for advanced Si devices. Band offset energies relative to Si are an important factor in determining tunneling leakage current, and internal photoemission. Studies by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and X-ray absorption spectroscopy (XAS) are combined with ab initio calculations to identify the compositional variation of the band-gap, and valence and conduction band offset energies of Zr silicate alloys with respect to Si. The minimum conduction band offset, due to DA - 2003/5/15/ PY - 2003/5/15/ DO - 10.1016/S0169-4332(03)00055-2 VL - 212 SP - 563-569 SN - 0169-4332 KW - ab initio quantum chemical calculations KW - plasma processing KW - Auger electron spectroscopy KW - X-ray photoelectron spectroscopy KW - X-ray absorption spectroscopy KW - zirconium silicate alloys KW - semiconductor-insulator interfaces ER - TY - JOUR TI - Domain structures in 6H-SiC wafers and their effect on the microstructures of GaN films grown on AlN and Al0.2Ga0.8N buffer layers AU - Preble, EA AU - Miraglia, PQ AU - Roskowski, AM AU - Vetter, WM AU - Dudley, M AU - Davis, RF T2 - JOURNAL OF CRYSTAL GROWTH AB - Silicon carbide wafers contain domains with varying sizes and degrees of tilt. The present research has shown that this microstructure is mimicked in GaN films deposited on AlN-containing buffer layers and that it masks most variations in the FWHM of the X-ray rocking curves of the former. The shape and FWHM in the GaN curves are determined both by domain tilting and dislocation broadening; the latter was dominant in areas of reduced tilt. Analyses of the on- and off-axis X-ray data acquired from these regions of lower tilt revealed the marked effect of the higher density of edge dislocations on broadening. This effect decreased with increasing GaN thickness due to dislocation annihilation. The densities of edge dislocations in GaN films deposited at 1010°C on pitted, less pitted and very smooth AlN layers of the same thickness grown at 1010°C, 1130°C and 1220°C, respectively, were lowest and highest in those films grown on the last two respective layers. Additional studies showed that GaN films grow on Al0.2Ga0.8N layers via step-flow and possess a lower edge dislocation density than films grown via the Stranski–Krastanov mode on AlN because of the reduced misfit and the absence of boundaries between coalesced islands. DA - 2003/10// PY - 2003/10// DO - 10.1016/S0022-0248(03)01515-X VL - 258 IS - 1-2 SP - 75-83 SN - 0022-0248 KW - characterization KW - defects KW - X-ray diffraction KW - metalorganic vapor phase epitaxy KW - nitrides KW - semiconducting silicon compounds ER - TY - JOUR TI - Device-quality GaN-dielectric interfaces by 300 degrees C remote plasma processing AU - Bae, C AU - Rayner, GB AU - Lucovsky, G T2 - APPLIED SURFACE SCIENCE AB - In previous studies, device-quality Si–SiO2 interfaces and dielectric bulk films (SiO2) were prepared using a two-step process; (i) remote plasma-assisted oxidation (RPAO) to form a superficially interfacial oxide (∼0.6 nm) and (ii) remote plasma enhanced chemical vapor deposition (RPECVD) to deposit the oxide film. The same approach has been applied to GaN–SiO2 system. Low-temperature (300 °C) remote N2/He plasma cleaning of the GaN surface, and the kinetics of GaN oxidation using RPAO process and subcutaneous oxidation during the SiO2 deposition using an RPECVD process have been investigated from analysis of on-line Auger electron spectroscopy (AES) features associated N and O. Compared to single-step SiO2 deposition, significantly reduced defect state densities are obtained at the GaN–dielectric interfaces by independent control of GaN–GaOx (x∼1.5) interface formation by RPAO, and SiO2 deposition by RPECVD. DA - 2003/6/30/ PY - 2003/6/30/ DO - 10.1016/S0169-4332(03)00497-5 VL - 216 IS - 1-4 SP - 119-123 SN - 1873-5584 KW - GaN-dielectric interfaces KW - surface leaning KW - subcutaneous oxidation KW - Ga2O3 KW - SiO2 KW - MOSd devices ER - TY - JOUR TI - Contributions to the infrared effective charges of oxides and chalcogenides from equilibrium charge and dynamic charge redistribution during normal mode motions AU - Sremaniak, LS AU - Whitten, JL AU - Menon, M AU - Lucovsky, G T2 - APPLIED SURFACE SCIENCE AB - Empirical force constant models for infrared (IR) and Raman scattering have emphasized differences between non-crystalline oxides and chalcogenides, attributing them to different bond angles at the two-fold coordinated O- and S(Se)-atoms in spite of the fact that both classes of materials form continuous random networks (CRNs) with equivalent 8N rule bonding coordination. This article applies ab initio electronic structure calculations to determine (i) equilibrium bonding geometries, and (ii) infrared effective charges for normal mode motions of O- and S-atoms in SiO2, and GeS2 and As2S3, respectively. Differences in equilibrium bond angles and normal mode effective charges are shown to result from quantitative differences in SiO, and GeS and GeSe bond ionicities that optimize the SiO2, and GeS2 and As2S3 total energies at markedly different bond angles. DA - 2003/5/15/ PY - 2003/5/15/ DO - 10.1016/S0169-4332(03)00087-4 VL - 212 SP - 839-843 SN - 0169-4332 KW - non-crystalline oxides and chalcogenides KW - continuous random networks KW - infrared active vibrations KW - infrared effective charges KW - Ab initio quantum chemistry calculations KW - normal mode motions ER - TY - JOUR TI - Band offset energies in zirconium silicate Si alloys AU - Lucovsky, G AU - Rayner, B AU - Zhang, Y AU - Appel, G AU - Whitten, J T2 - APPLIED SURFACE SCIENCE AB - Transition metal silicates, (ZrO2)x(SiO2)1−x, with dielectric constants, k>10 have been proposed as alternative dielectrics for advanced Si devices. Studies by X-ray absorption, X-ray photoelectron and Auger electron spectroscopy are combined to identify the compositional variation of the valence and conduction band offset energies with respect to Si in Zr silicate alloys. The minimum conduction band offset energy, associated with localized Zr 4d∗-states, is ∼1.4 eV, and is independent of alloy composition, while valence band offsets decrease monotonically with increasing ZrO2 content. Differences between the coupling of tunneling electrons to localized Zr 4d∗ and extended Si 3s∗ states, characterized by respective tunneling masses of ∼0.5mo and ∼0.2mo, combine to contribute to a minimum in the direct tunneling current in the mid-silicate-alloy composition range, x∼0.4–0.6. DA - 2003/6/30/ PY - 2003/6/30/ DO - 10.1016/S0169-4332(03)00429-X VL - 216 IS - 1-4 SP - 215-222 SN - 0169-4332 KW - plasma processing and deposition KW - Auger electron spectroscopy KW - X-ray photoelectron spectroscopy KW - X-ray absorption spectroscopy KW - zirconium silicate alloys KW - semiconductor-dielectric band offset energies ER - TY - JOUR TI - A novel technique for making self-encapsulated and self-aligned copper films AU - Chugh, A AU - Tiwari, A AU - Kvit, A AU - Narayan, J T2 - MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY AB - We provide a method to grow self-aligned epitaxial MgO/Cu/MgO films on silicon substrates by pulsed laser deposition (PLD) technique. Here, a thin layer of Cu/Mg (Mg 5%) is deposited using a PLD over Si (100) specimens, followed by annealing at 500 °C in a controlled oxygen environment resulting in the segregation of Mg on either side of the copper film. Mg on the upper side of copper reacts with ambient oxygen and on the lower side with the adsorbed oxygen in the substrate to form layers of MgO. High-resolution transmission electron microscopy (HRTEM) measurements showed thin layers of MgO formed on either side of the copper films. The lower MgO layer acts as a diffusion barrier and inhibits the diffusion of Cu into the system while the upper MgO layer acts as a passivating layer and protects copper against oxidation. This approach can also be used to grow high quality epitaxial YBa2Cu3O7−δ films with MgO acting as a buffer for the superconducting device applications. DA - 2003/9/25/ PY - 2003/9/25/ DO - 10.1016/s0921-5107(03)00148-x VL - 103 IS - 1 SP - 45-48 SN - 0921-5107 KW - pulsed laser ablation KW - self-aligned passivated contacts KW - domain matching epitaxy KW - transmission electron microscopy KW - annealing ER - TY - JOUR TI - Thermal conductivity of epitaxially textured diamond films AU - Wolter, SD AU - Borca-Tasciuc, DA AU - Chen, G AU - Govindaraju, N AU - Collazo, R AU - Okuzumi, F AU - Prater, JT AU - Sitar, Z T2 - DIAMOND AND RELATED MATERIALS AB - The in-plane thermal conductivity of epitaxially textured, (1 0 0) diamond has been evaluated in comparison to (1 0 0) diamond possessing a random fiber texture. The diamond films were bias-enhanced nucleated using an alternating current source and grown on (1 0 0) silicon using microwave plasma chemical vapor deposition. Thermal conductivity values of ∼1120 (±11%) W/m K and ∼550 (±11%) W/m K were determined for the epitaxial versus non-epitaxial diamond, respectively, using Joule heating thermometry. This twofold improvement in the thermal conductivity of the epitaxially textured diamond is ascribed to a reduction in the grain boundary defects within the film. DA - 2003/1// PY - 2003/1// DO - 10.1016/S0925-9635(02)00248-0 VL - 12 IS - 1 SP - 61-64 SN - 0925-9635 KW - epitaxial diamond KW - thermal conductivity KW - joule heating thermometry ER - TY - JOUR TI - Study of the dielectric function of ZnS by spectroscopic ellipsometry AU - Ghong, T. H. AU - Kim, T. J. AU - Kim, Y. D. AU - Kim, S. J. AU - Aspnes, D. E. AU - Choi, Y. D. AU - Yu, Y. M. T2 - Journal of the Korean Physical Society DA - 2003/// PY - 2003/// VL - 42 IS - 2003 Feb SP - S238-241 ER - TY - JOUR TI - Structural dependence of breakdown characteristics and electrical degradation in ultrathin RPECVD oxide/nitride gate dielectrics under constant voltage stress AU - Lee, YM AU - Wu, YD AU - Bae, C AU - Hong, JG AU - Lucovsky, G T2 - SOLID-STATE ELECTRONICS AB - Abstract The structural dependence of breakdown characteristics and electrical degradation in ultrathin oxide/nitride (O/N) dielectrics, prepared by remote plasma enhanced chemical vapor deposition, is investigated under constant voltage stress. In the early stage of oxide wearout, soft breakdown is a local phenomenon dominated by the tunneling current. After a given period of stress, a strong channel-length dependence of dielectric breakdown and the corresponding stress-induced leakage current from the evolution of increased tunneling current have been found. Stacked O/N dielectrics with interface nitridation demonstrate improved device performance on subthreshold swing and threshold voltage shifts after stress, indicating the suppression of stress-induced traps at the oxide/Si and oxide/drain interfaces compared to thermal oxides. Experimental evidence shows more severe breakdown and device degradation in the threshold voltage, drain current and transconductance for shorter channel PMOSFETs with O/N dielectrics. These degradations result from the enhancement of hole trapping in the gate–drain overlap region as evidenced by a positive off-state leakage current, which leads to hard breakdown, and the complete failure of device functionality. DA - 2003/1// PY - 2003/1// DO - 10.1016/S0038-1101(02)00257-5 VL - 47 IS - 1 SP - 71-76 SN - 1879-2405 KW - dielectric degradation KW - soft breakdown KW - RPECVD oxide/nitride dielectric KW - stress-induced leakage current KW - constant voltage stress KW - hard breakdown ER - TY - JOUR TI - Optical properties of InGaAs alloy films in the E-2 region by spectroscopic ellipsometry AU - Ihn, Y. S. AU - Ghong, T. H. AU - Kim, Y. D. AU - Kim, S. J. AU - Aspnes, D. E. AU - Yao, T. AU - Koo, B. H. T2 - Journal of the Korean Physical Society DA - 2003/// PY - 2003/// VL - 42 IS - 2003 Feb SP - S242-245 ER - TY - JOUR TI - Electron energy distribution during high-field transport in AlN AU - Collazo, R AU - Schlesser, R AU - Roskowski, A AU - Miraglia, P AU - Davis, RF AU - Sitar, Z T2 - JOURNAL OF APPLIED PHYSICS AB - The energy distribution of electrons transported through intrinsic AlN heteroepitaxial films grown on SiC was directly measured as a function of applied field and AlN film thickness. Following the transport, electrons were extracted into vacuum through a semitransparent Au electrode and their energy distribution was measured using an electron spectrometer. Transport through films thicker than 95 nm at an applied field between 200 and 350 kV/cm occurred as steady-state hot electron transport following a Maxwellian energy distribution with a characteristic carrier temperature. At higher fields (470 kV/cm), intervalley scattering was evidenced by a multicomponent energy distribution featuring a second peak at the energy position of the first satellite valley. Velocity overshoot was observed in films thinner than 95 nm and at fields greater than 550 kV/cm. In this case, a symmetric energy distribution centered at an energy above the conduction band minimum was measured, indicating that the drift component of the electron velocity was on the order of the “thermal” component. A transient transport length of less than 80 nm was deduced from these observations. DA - 2003/3/1/ PY - 2003/3/1/ DO - 10.1063/1.1543633 VL - 93 IS - 5 SP - 2765-2771 SN - 0021-8979 ER - TY - JOUR TI - Combined atomic force microscopy and scanning tunneling microscopy imaging of cross-sectioned GaN light-emitting diodes AU - Bender, J. W. AU - Salmon, M. E. AU - Russell, P. E. T2 - Scanning DA - 2003/// PY - 2003/// VL - 25 IS - 1 SP - 45-51 ER - TY - JOUR TI - Local electrostatic effects of surface structure on field emission AU - Jaeger, DL AU - Hren, JJ AU - Zhirnov, , VV T2 - JOURNAL OF APPLIED PHYSICS AB - We examined the classical electrostatic effects due to geometric surface structures on conductive field emission needles numerically using the finite element method and compared our results to several commonly applied analytic relations. Analysis of the morphology of electrochemically prepared Mo needles by high-resolution transmission electron microscopy was incorporated in the numerical analysis in the form of small surface protrusions and gross needle shape. We found that the error between the electrostatic potential defined by popular analytic equations and both analytic equations derived in prolate spheroidal coordinates and finite element method results was significant for ellipsoidal needles with and without surface protrusions. The morphology of the surface protrusion was found to introduce a significant nonlinear potential barrier near the needle surface. Finally we numerically analyzed a nonsymmetric, nonhomogeneous experimental needle indicating that even larger errors in the electrostatic potential can be expected relative to analytic equations. DA - 2003/1/1/ PY - 2003/1/1/ DO - 10.1063/1.1526934 VL - 93 IS - 1 SP - 691-697 SN - 1089-7550 ER - TY - JOUR TI - Microscopic mapping of strain relaxation in uncoalesced pendeoepitaxial GaN on SiC AU - Schwarz, U. T. AU - Schuck, P. J. AU - Mason, M. D. AU - Grober, R. D. AU - Roskowski, A. M. AU - Einfeldt, S. AU - Davis, R. F. T2 - Physical Review. B, Condensed Matter and Materials Physics DA - 2003/// PY - 2003/// VL - 67 IS - 4 SP - 045321-1 ER - TY - JOUR TI - Voltage-controlled RF filters employing thin-film barium-strontium-titanate tunable capacitors AU - Tombak, A AU - Maria, JP AU - Ayguavives, FT AU - Jin, Z AU - Stauf, GT AU - Kingon, AI AU - Mortazawi, A T2 - IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES AB - Tunable lowpass and bandpass lumped-element filters employing barium-strontium-titanate (BST)-based capacitors are presented. A new metallization technique is used, which improves the quality factor of the tunable BST capacitors by a factor of two. The lowpass filter has an insertion loss of 2 dB and a tunability of 40% (120-170 MHz) with the application of 0-9 V DC bias. The bandpass filter (BPF) has an insertion loss of 3 dB and a tunability of 57% (176-276 MHz) with the application of 0-6 V DC. The third-order intercept point of the BPF was measured to be 19 dBm with the application of two tones around 170 MHz. DA - 2003/2// PY - 2003/2// DO - 10.1109/TMTT.2002.807822 VL - 51 IS - 2 SP - 462-467 SN - 1557-9670 KW - barium-strontium-titanate.(BST) KW - ferroelectric KW - intermodulation distortion KW - metalorganic chemical vapor deposition (MOCVD) KW - multilayer ground plane KW - paraelectric KW - tunable bandpass filter (BPF) KW - tunable lowpass filter (LPF) ER - TY - JOUR TI - Response to "Comment on 'Pd growth and subsequent Schottky barrier formation on chemical vapor cleaned p-type GaN surfaces' [J. Appl. Phys. 91, 732 (2002)]" AU - Hartlieb, PJ AU - Roskowski, A AU - Davis, RF AU - Platow, W AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS DA - 2003/3/15/ PY - 2003/3/15/ DO - 10.1063/1.1542911 VL - 93 IS - 6 SP - 3679-3679 SN - 0021-8979 ER - TY - JOUR TI - Plasma plume characteristics and properties of pulsed laser deposited diamond-like carbon films AU - Haverkamp, J AU - Mayo, RM AU - Bourham, MA AU - Narayan, J AU - Jin, C AU - Duscher, G T2 - JOURNAL OF APPLIED PHYSICS AB - Pulsed laser deposition is a unique technique for the deposition of hydrogen-free diamond-like carbon films. During deposition, amorphous carbon is evaporated from a solid target by a high-energy KrF laser, ionized, and ejected as a plasma plume. The plume expands outwards and deposits the target material on a substrate. The plasma properties of the plume determine the quality of the thin films deposited on the substrate. These plume properties include ion density, ion flow speed, electron temperature, and plume peaking parameter. In this research, a triple Langmuir probe is used to determine various plasma properties of the plume created from the pulsed laser ablation of amorphous graphite as a function of laser energy density and laser spot size on the target. A thin diamond-like carbon film is deposited and analyzed with electron energy-loss spectroscopy to determine the sp3/sp2 fraction. A special preparation technique was used to prepare the thin film for analysis to prevent the damage that may be caused by conventional ion milling techniques. DA - 2003/3/15/ PY - 2003/3/15/ DO - 10.1063/1.1555695 VL - 93 IS - 6 SP - 3627-3634 SN - 1089-7550 ER - TY - JOUR TI - Grinding temperature measurements in magnesia-partially-stabilized zirconia using infrared spectrometry AU - Curry, AC AU - Shih, AJ AU - Kong, J AU - Scattergood, RO AU - McSpadden, SB T2 - JOURNAL OF THE AMERICAN CERAMIC SOCIETY AB - Results of temperature measurements by analysis of the thermal emission spectra generated during grinding and subsequently transmitted through partially stabilized zirconia workpieces are presented. Portions of emitted visible and near-infrared spectra were collected with spectrometers. Source temperatures were determined by fitting the scaled spectrometer output spectra to blackbody curves. Simulations showed that the effective temperatures determined by this method will be strongly biased toward hot-spot (flash) temperatures, which are expected to occur at the grinding grit–workpiece interface. Hot-spot temperatures on the order of 3000 K were obtained for grinding with both SiC and diamond wheels. These high temperatures modify the grinding process and the phase content of grinding chips. DA - 2003/2// PY - 2003/2// DO - 10.1111/j.1151-2916.2003.tb00019.x VL - 86 IS - 2 SP - 333-341 SN - 1551-2916 ER - TY - JOUR TI - Fibrous structures on diamond and carbon surfaces formed by hydrogen plasma under direct current bias and field electron-emission properties AU - Kobashi, K AU - Tachibana, T AU - Yokota, Y AU - Kawakami, N AU - Hayashi, K AU - Yamamoto, K AU - Koga, Y AU - Fujiwara, S AU - Gotoh, Y AU - Nakahara, H AU - Tsuji, H AU - Ishikawa, J AU - Kock, FA AU - Nemanich, RJ T2 - JOURNAL OF MATERIALS RESEARCH DA - 2003/2// PY - 2003/2// DO - 10.1557/JMR.2003.0042 VL - 18 IS - 2 SP - 305-326 SN - 2044-5326 ER - TY - JOUR TI - Comparative investigation of photoluminescence of In- and Si- doped GaN/AlGaN multi-quantum wells AU - Wang, LS AU - Sun, WH AU - Chua, SJ AU - Johnson, M T2 - MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY AB - This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief and author, as the authors have plagiarized part of a paper that had already appeared in Mater. Res. Soc. Symp. Proc., 719 (2002) 371–376. One of the conditions of submission of a paper for publication is that authors declare explicitly that their work is original and has not appeared in a publication elsewhere. Re-use of any data should be appropriately cited. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process. DA - 2003/1/25/ PY - 2003/1/25/ DO - 10.1016/s0921-5107(02)00572-x VL - 97 IS - 2 SP - 196-199 SN - 0921-5107 KW - GaN/AlGaN multiquantum wells KW - photoluminescence KW - indium and silicon doings ER - TY - CONF TI - Optimization of nitrogen removal from anaerobically-pretreated swine wastewater in intermittent aeration tanks AU - Hu, Z. AU - Mota, C. R., III AU - Reyes F. L., AU - Cheng, J. C2 - 2003/// C3 - Animal, Agricultural and Food Processing Wastes IX : proceedings of the Ninth International Symposium, 12-15 October, 2003, Raleigh, North Carolina DA - 2003/// VL - 9 SN - 1892769328 ER - TY - JOUR TI - Synthesis, characterization, and direct observation of star microgels AU - Gurr, PA AU - Qiao, GG AU - Solomon, DH AU - Harton, SE AU - Spontak, RJ T2 - MACROMOLECULES AB - The molecular sizes of four star microgels, synthesized by atom transfer radical polymerization of poly(methyl methacrylate) (PMMA) with ethylene glycol dimethacrylate as the cross-linker, have been investigated by light scattering methods and transmission electron microscopy (TEM). Gel permeation chromatography right-angle laser light scattering performed with a triple detector system and dynamic light scattering together confirm that individual particles of one star microgel in tetrahydrofuran and styrene solutions possess mean diameters of 31 and 18 nm, respectively. Complementary TEM reveals that another star microgel appears as discrete particles measuring 18−30 nm in diameter when added to styrene monomer subsequently polymerized to form a solid matrix. These particles likewise undergo macrophase separation to form microgel-rich domains consisting of nanoscale PMMA channels. Additional TEM examination of a star microgel deposited by dilute solution casting provides direct evidence for the existence of individual microgel molecules with a mean (dry) diameter of ∼15 nm. DA - 2003/7/29/ PY - 2003/7/29/ DO - 10.1021/ma030122m VL - 36 IS - 15 SP - 5650-5654 SN - 0024-9297 ER - TY - JOUR TI - Pulsed laser deposition of Bi2Te3-based thermoelectric thin films AU - Makala, RS AU - Jagannadham, K AU - Sales, BC T2 - JOURNAL OF APPLIED PHYSICS AB - Thin films of p-type Bi0.5Sb1.5Te3, n-type Bi2Te2.7Se0.3, and n-type (Bi2Te3)90(Sb2Te3)5(Sb2Se3)5 (with 0.13 wt % SbI3) were deposited on substrates of mica and aluminum nitride (on silicon) using pulsed laser ablation at substrate temperatures between 300 °C to 500 °C. The films were characterized using x-ray diffraction and transmission electron microscopy for crystalline quality and epitaxial growth on the substrates. The surface morphology and microstructure were examined using scanning electron microscopy. X-ray mapping and energy-dispersive spectroscopy were performed to determine nonstoichiometry in the composition and homogeneity. The quality of the films, in terms of stoichiometric composition and crystal perfection, was studied as a function of growth temperature and laser fluence. The values of the Seebeck coefficient, electrical resistivity, and Hall mobility in the thin films were measured and compared with those in the bulk. Thermoelectric figure of merit of the films was evaluated from the measured parameters. Correlation of the thermoelectric properties, with the crystalline quality and stoichiometric composition of the films, showed the advantages of pulsed laser deposition of the multicomponent thermoelectric thin films. The results illustrate that laser physical vapor deposition is a suitable choice for deposition of multicomponent thermoelectric films. However, optimization of target composition, substrate temperature, and annealing of the films after deposition were found necessary to maintain the desired stoichiometry and low defect density. AlN/Si substrates provided better quality films compared to substrates of mica. Poor adhesion and cracking of the films on mica were found to be detrimental factors. Films deposited on AlN/Si substrates were found to show higher carrier mobility and higher values of Seebeck coefficient. DA - 2003/9/15/ PY - 2003/9/15/ DO - 10.1063/1.1600524 VL - 94 IS - 6 SP - 3907-3918 SN - 1089-7550 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0141990549&partnerID=MN8TOARS ER - TY - JOUR TI - Optimization of strength and ductility in nanocrystalline and ultrafine grained metals AU - Koch, CC T2 - SCRIPTA MATERIALIA AB - The possible optimization of strength and ductility in nanocrystalline and ultrafine grained metals is assessed. Most nanocrystalline metals show little ductility while exhibiting enhanced strength. The possibility that these properties can be optimized is discussed for microstructures with appropriate grain size distributions, and the introduction of second phase particles. DA - 2003/10// PY - 2003/10// DO - 10.1016/S1359-6462(03)00394-4 VL - 49 IS - 7 SP - 657-662 SN - 1359-6462 KW - nanocrystalline metals KW - ultrafine grained metals KW - yield strength KW - ductility ER - TY - JOUR TI - Optimization of secondary ion mass spectrometry detection limit for N in SiC AU - Pivovarov, AL AU - Stevie, FA AU - Griffis, DP AU - Guryanov, GM T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Controlled changes in the Cs+ primary ion beam density and analytical expressions describing the sources (bulk concentration, memory effect, and adsorption of N from the residual vacuum) of secondary ion mass spectrometry analyte secondary ion intensities were used to determine the contributions to the N secondary ion intensity obtained during the analysis of trace levels of N in bulk SiC. This methodology allows the determination of N concentrations that can be substantially less than the apparent N secondary ion background intensity. It was shown that for the Cameca IMS-6F instrumental conditions used, memory effect is the main contributor to the N background signal. Taking into consideration the Cs+ beam diameter, the raster size, the diameter of the ion-extracted area, and the impurity secondary ion intensity, an optimized combination of primary ion beam current and raster size was determined that resulted in the best detection limit for N in bulk SiC. This detection limit for N in bulk SiC (∼6×1014 atoms/cm3) was obtained for a primary ion current of 100 nA, a raster size of 45 μm×45 μm, and a secondary ion extraction area diameter of 30 μm. DA - 2003/// PY - 2003/// DO - 10.1116/1.1595108 VL - 21 IS - 5 SP - 1649-1654 SN - 0734-2101 ER - TY - JOUR TI - Mechanisms limiting electron field emission from diamond AU - Schlesser, R. AU - McClure, M. T. AU - Sitar, Z. T2 - New Diamond and Frontier Carbon Technology DA - 2003/// PY - 2003/// VL - 13 IS - 5 SP - 285-295 ER - TY - JOUR TI - Experimental and numerical method for determining temperature distribution in a wood cutting tool AU - Sheikh-Ahmad, JY AU - Lewandowski, CM AU - Bailey, JA AU - Stewart, JS T2 - EXPERIMENTAL HEAT TRANSFER AB - Abstract A 2-D boundary-element model was used to solve the steady-state heat conduction problem in a wood cutting tool. Cutting experiments were conducted in order to measure temperatures at remote locations on the tool rake face and at the tool/holder interface. The tool/holder interface temperatures were used as inputs into the boundary-element model. Heat input into the tool was adjusted until predicted temperatures on the rake face agreed with experimental results. The proportion of the machining power conducted into the tool as heat was determined as a function of the cutting geometry, specific cutting energy, and cutting speed. DA - 2003/// PY - 2003/// DO - 10.1080/08916150390223092 VL - 16 IS - 4 SP - 255-271 SN - 0891-6152 ER - TY - JOUR TI - Band offset measurements of the Si3N4/GaN (0001) interface AU - Cook, TE AU - Fulton, CC AU - Mecouch, WJ AU - Davis, RF AU - Lucovsky, G AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy were used to measure electronic states as Si3N4 was deposited on clean GaN (0001) surfaces. The n-type (2×1018) and p-type (1×1017) GaN surfaces were atomically cleaned in NH3 at 860 °C, and the n-and p-type surfaces showed upward band bending of ∼0.2±0.1 eV and downward band bending of 1.1±0.1 eV, respectively, both with an electron affinity of 3.1±0.1 eV. Layers of Si (∼0.2 nm) were deposited on the clean GaN and nitrided using an electron cyclotron resonance N2 plasma at 300 °C and subsequently annealed at 650 °C for densification into a Si3N4 film. Surface analysis was performed after each step in the process, and yielded a valence band offset of 0.5±0.1 eV. Both interfaces exhibited type II band alignment where the valence band maximum of GaN lies below that of the Si3N4 valence band. The conduction band offset was deduced to be 2.4±0.1 eV, and a change of the interface dipole of 1.1±0.1 eV was observed for Si3N4/GaN interface formation. DA - 2003/9/15/ PY - 2003/9/15/ DO - 10.1063/1.1601314 VL - 94 IS - 6 SP - 3949-3954 SN - 0021-8979 ER - TY - JOUR TI - The stress-strain behavior of polymer-nanotube composites from molecular dynamics simulation AU - Frankland, SJV AU - Harik, VM AU - Odegard, GM AU - Brenner, DW AU - Gates, TS T2 - COMPOSITES SCIENCE AND TECHNOLOGY AB - Stress–strain curves of polymer–carbon nanotube composites generated from molecular dynamics simulations of a single-walled carbon nanotube embedded in polyethylene are presented. A comparison is made between the response to mechanical loading of a composite with a long, continuous nanotube (replicated via periodic boundary conditions) and the response of a composite with a short, discontinuous nanotube. Both composites are mechanically loaded in the direction of, and transverse to, the nanotube axis. The long-nanotube composite shows an increase in the stiffness relative to the polymer and behaves anisotropically under the different loading conditions considered. The short-nanotube composite shows no enhancement relative to the polymer, most probably because of its low aspect ratio. The stress–strain curves from molecular dynamics simulations are compared with corresponding rule-of-mixtures predictions. DA - 2003/8// PY - 2003/8// DO - 10.1016/S0266-3538(03)00059-9 VL - 63 IS - 11 SP - 1655-1661 SN - 0266-3538 KW - polymer-matrix composites (PMCs) KW - mechanical properties KW - stress/strain curves KW - computational simulation KW - carbon nanotubes ER - TY - JOUR TI - Mechanical properties of Nylon bonded Nd-Fe-B permanent magnets AU - Garrell, MG AU - Shih, AJ AU - Ma, BM AU - Lara-Curzio, E AU - Scattergood, RO T2 - JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS AB - Tensile and flexural strengths as well as Young's modulus of Polyamide-11 (Nylon-11) based injection molded Nd–Fe–B magnets have been determined from −40°C to 100°C. Two types of Nd–Fe–B powders were included in this study. One is the conventional melt spun powder of irregular shape, the other is the atomized powder of spherical morphology. It was found that the tensile strength varies significantly with both test temperature and morphology of Nd–Fe–B powder. For a fixed volume fraction of magnet powder, the tensile strength decreases with increasing temperature. For bonded magnets made of melt spun powder, the tensile strength increases with increasing volume fraction of magnet powder. Specimens made of spherical atomized powders exhibit much lower tensile strength and better flexibility when compared to those made of melt spun powder. Scanning electron microscopy (SEM) analysis indicated that the debonding at the Nd–Fe–B powder and Nylon interface is the main cause of failure at 23°C and 100°C. At −40°C, a different failure mechanism with the fracture of Nd–Fe–B particle was observed on magnets prepared from melt spun powders. For the specimen containing 59.7 vol% of melt spun powder, a bending strength of 41 MPa and dynamic Young's modulus of 12.7 GPa were obtained. DA - 2003/2// PY - 2003/2// DO - 10.1016/S0304-8853(02)00983-6 VL - 257 IS - 1 SP - 32-43 SN - 0304-8853 KW - bonded magnets KW - melt spun NdFeB KW - atomized NdFeB KW - mechanical properties ER - TY - JOUR TI - Low temperature semiconductor surface passivation for nanoelectronic device applications AU - Bae, C AU - Lucovsky, G T2 - SURFACE SCIENCE AB - Abstract A low temperature remote plasma assisted oxidation (RPAO) process for interface formation and passivation has been extended from Si and SiC to GaN. The process, which can be applied to nanoscale structures including quantum dots and wires, provides excellent control of ultra-thin interfacial layers which passivate the GaN substrate, preventing a parasitic or subcutaneous oxidation of the substrate during plasma deposition of SiO 2 . This remote plasma processing for GaN-dielectric heterostructures includes: (i) an in situ nitrogen plasma surface clean, (ii) RPAO for formation of an interfacial GaO x transition region between the GaN and deposited dielectric, and (iii) a remote plasma enhanced chemical vapor deposition of an SiO 2 dielectric. DA - 2003/6/10/ PY - 2003/6/10/ DO - 10.1016/S0039-6028(03)00181-X VL - 532 SP - 759-763 SN - 0039-6028 KW - plasma processing KW - Auger electron spectroscopy KW - semiconductor-insulator interfaces KW - interface states ER - TY - JOUR TI - Growth kinetics and thermal stress in AlN bulk crystal growth AU - Wu, B AU - Ma, RH AU - Zhang, H AU - Dudley, M AU - Schlesser, R AU - Sitar, Z T2 - JOURNAL OF CRYSTAL GROWTH AB - Group III nitrides, such as GaN, AlN and InGaN, have attracted great attention due to their applications in blue-green and ultraviolet light emitting diodes and lasers. In this paper, an integrated model has been developed based on the conservation of momentum, mass, chemical species and energy together with boundary conditions that account for heterogeneous chemical reactions both at the source and seed surfaces. The predicted temperature profiles have been compared with measurements for different power levels and flow rates in a reactor for AlN crystal growth at the North Carolina State University. We have found that the heat power level affects the entire temperature distribution greatly while the flow rate has insignificant effect on the temperature distribution; the overall thermal stress level is higher than the critical resolved shear stress, indicating that thermal elastic stress can be a major source to induce high dislocation density in the as-grown crystal. The stress level is strongly dependent on the temperature gradient in the as-grown crystal. Results are correlated well with defects showing in an X-ray topograph for the AlN plate crystal. DA - 2003/6// PY - 2003/6// DO - 10.1016/S0022-0248(03)01044-3 VL - 253 IS - 1-4 SP - 326-339 SN - 1873-5002 KW - computer simulation KW - growth models KW - growth from vapor KW - single crystal growth KW - chemical vapor deposition processes KW - nitrides ER - TY - JOUR TI - Grain size dependence of the plastic deformation kinetics in Cu AU - Conrad, H T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Data on the effect of grain size d in the range of nm to mm on the plastic deformation kinetics of Cu at 77–373 K are analyzed to determine the influence of grain size on the strain rate-controlling mechanism. Three grain size regimes were identified: Regimes I (d≈10−6–10−3 m), II (d≈10−8–10−6 m) and III (d<∼10−8 m). A dislocation cell structure characterizes Regime II, which no longer occurs in Regime II. The absence of all intragranular dislocation activity characterizes Regime III. The following mechanisms were concluded to be rate-controlling for ε̇≈10−5–10−3s−1: (a) Regime I, intersection of dislocations; (b) Regime I, grain boundary shear promoted by dislocation pile-ups; and (c) Regime III, grain boundary shear. The major effect of grain size on the intersection mechanism in Regime I is on the mobile and forest dislocation densities; the effect in Regime II is on the number of dislocations and on the number of grain boundary atom sites; the effect in Regime III is on the number of grain boundary atom sites. The transition grain size from one regime to another depends on the strain rate and temperature. Crystallographic texture is also important. DA - 2003/1/20/ PY - 2003/1/20/ DO - 10.1016/s0921-5093(02)00238-1 VL - 341 IS - 1-2 SP - 216-228 SN - 1873-4936 KW - copper KW - dislocations KW - grain boundaries KW - thermally-activated processes KW - Hall-Petch constants ER - TY - JOUR TI - Gold Schottky contacts on oxygen plasma-treated, n-type ZnO(000(1)over-bar) AU - Coppa, BJ AU - Davis, RF AU - Nemanich, RJ T2 - APPLIED PHYSICS LETTERS AB - Reverse bias current–voltage measurements of ∼100-μm-diameter gold Schottky contacts deposited on as-received, n-type ZnO(0001̄) wafers and those exposed for 30 min to a remote 20% O2/80% He plasma at 525±20 °C and cooled either in vacuum from 425 °C or the unignited plasma gas have been determined. Plasma cleaning resulted in highly ordered, stoichiometric, and smooth surfaces. Contacts on as-received material showed μA leakage currents and ideality factors &gt;2. Contacts on plasma-cleaned wafers cooled in vacuum showed ∼36±1 nA leakage current to −4 V, a barrier height of 0.67±0.05 eV, and an ideality factor of 1.86±0.05. Cooling in the unignited plasma gas coupled with a 30 s exposure to the plasma at room temperature resulted in decreases in these parameters to ∼20 pA to −7 V, 0.60±0.05 eV, and 1.03±0.05, respectively. Differences in the measured and theoretical barrier heights indicate interface states. (0001) and (0001̄) are used in this letter to designate the polar zinc- and oxygen-terminated surfaces, respectively. DA - 2003/1/20/ PY - 2003/1/20/ DO - 10.1063/1.1536264 VL - 82 IS - 3 SP - 400-402 SN - 0003-6951 ER - TY - JOUR TI - Genome studies and molecular genetics - The rice genome and comparative genomics of higher plants - Editorial overview AU - Sasaki, T AU - Sederoff, RR T2 - CURRENT OPINION IN PLANT BIOLOGY AB - Rice varieties vary in their capacity for callus induction, growth, and regeneration. We identified the locus and candidate gene which conferred good callus growth and regenerative ability in the rice variety Koshihikari, a notorious poor rice line for genetic transformation. In addition, we succeeded in establishment of a new selectable marker system using the NiR gene for Agrobacterium-mediated transformation of rice, c.v. “Koshihikari.” The locus was mapped onto chromosome 1, and the nearest RFLP marker was C0178. A total of 500 segregating individuals (BC6F2 seeds) were screened for recombination by PCR-based screening and its location narrowed to a 540-kb region that had been sequenced by the International Rice Genome Sequencing Project. One ORF encoded a putative ferredoxin-nitrite reductase (NiR), which has been suggested to be required for callus induction and growth. The growth and regeneration ability of the calli initiated from Koshihikari was improved through integration of the NiR gene from Konansou. Analysis of ORFs and the promoter region of NiR indicated that the promoter region of NiR gene is responsible for growth and regeneration ability of calli in rice, c.v. Koshihikari. We established a NiR selection system for Agrobacterium-mediated transformation in rice, c.v. Koshihikari, by integration of the NiR gene isolated from rice c.v. Konansou. Transgenic rice plants regenerated from selected calli exhibited β-glucuronidase (GUS) activity. A transformation frequency of 9% was obtained. The results indicated that the NiR selection system is devoid of the disadvantages and concerns of using foreign genes (antibiotics and herbicide resistant) for selection. DA - 2003/4// PY - 2003/4// DO - 10.1016/S1369-5266(03)00018-9 VL - 6 IS - 2 SP - 97-100 SN - 1369-5266 ER - TY - JOUR TI - Composite electrolytes from self-assembled colloidal networks AU - Walls, HJ AU - Riley, MW AU - Fedkiw, PS AU - Spontak, RJ AU - Baker, GL AU - Khan, SA T2 - ELECTROCHIMICA ACTA AB - In this study, we present two approaches to developing composite electrolytes exploiting the self-assembling nature of colloidal fillers. The first system comprises of oligomers of poly(ethylene glycol) dimethyl ether, branched fumed silica particulates and lithium salt. The fumed silica forms a three-dimensional, self-supporting network that provides mechanical stability. The large pores of the network has little effect on diffusivity of ions and oligomers, lithium transference number and ionic conductivity, with the latter showing values >10−3 S/cm at ambient conditions. The second system consists of Li exchanged hectorite clay in a mixture of low molar mass carbonates. Similar to the fumed silica, the clay provides mechanical stability through formation of a three-dimensional network. In addition, the immobile clay platelets also serve as the anion rendering the system to be a single ion conductor. Near-unity transference number is observed in this case. However, the room temperature conductivity of the clay composite is lower than the fumed silica, revealing a value of about 10−4 S/cm. The lower conductivity can be attributed to the clay not being in a fully exfoliated form as evident from morphological analysis. DA - 2003/6/30/ PY - 2003/6/30/ DO - 10.1016/S0013-4686(03)00187-7 VL - 48 IS - 14-16 SP - 2071-2077 SN - 0013-4686 KW - composite electrolytes KW - colloidal networks KW - oligomers ER - TY - JOUR TI - Bonding and stability of hybrid diamond/nanotube structures AU - Shenderova, OA AU - Areshkin, D AU - Brenner, DW T2 - MOLECULAR SIMULATION AB - Geometrical considerations combined with detailed atomic modeling are used to define general classes of diamond/carbon nanotube interface structures with low residual stresses and no unsatisfied bonding. Chemically and mechanically robust interfaces are predicted, supporting recent experimental studies in which structures of this type were proposed. DA - 2003/4// PY - 2003/4// DO - 10.1080/0892702021000049691 VL - 29 IS - 4 SP - 259-268 SN - 1029-0435 KW - hybrid structures KW - diamond KW - nanotube KW - bonding and stability ER - TY - JOUR TI - Effect of microstructure on diffusion of copper in TiN films AU - Gupta, A AU - Wang, H AU - Kvit, A AU - Duscher, G AU - Narayan, J T2 - JOURNAL OF APPLIED PHYSICS AB - We investigated the effect of the microstructure of TiN films on the diffusion behavior of Cu. Cu/TiN films were synthesized on Si(100) substrate by the pulsed laser deposition (PLD) technique. Three different microstructures of TiN were achieved by growing the films at different substrate temperatures, where higher deposition temperatures (∼650 °C) led to epitaxial growth by the mechanism of domain matching epitaxy and lower temperature depositions resulted in polycrystalline and nanocrystalline TiN films. These structures were characterized using x-ray diffraction and high-resolution transmission electron microscopy. Cu was deposited in situ on the samples with three different microstructures of TiN films on Si(100) by PLD. All three samples were simultaneously annealed at 500 °C for 30 min in high vacuum to study the effect of diffusion characteristics of Cu as a function of microstructure of the TiN films. Secondary ion mass spectroscopy, Z-contrast imaging and electron energy-loss spectroscopy were used to understand the diffusion mechanisms and rationalize results in different microstructures. DA - 2003/5/1/ PY - 2003/5/1/ DO - 10.1063/1.1566472 VL - 93 IS - 9 SP - 5210-5214 SN - 1089-7550 ER - TY - JOUR TI - Domain epitaxy: A unified paradigm for thin film growth AU - Narayan, J AU - Larson, BC T2 - JOURNAL OF APPLIED PHYSICS AB - We present a unified model for thin film epitaxy where single crystal films with small and large lattice misfits are grown by domain matching epitaxy (DME). The DME involves matching of lattice planes between the film and the substrate having similar crystal symmetry. In this framework, the conventional lattice matching epitaxy becomes a special case where a matching of lattice constants or the same planes is involved with a small misfit of less than 7%–8%. In large lattice mismatch systems, we show that epitaxial growth of thin films is possible by matching of domains where integral multiples of major lattice planes match across the interface. We illustrate this concept with atomic-level details in the TiN/Si(100) with 3/4 matching, the AlN/Si(100)with 4/5 matching, and the ZnO/α−Al2O3(0001) with 6/7 matching of major planes across the film/substrate interface. By varying the domain size, which is equal to intregral multiple of lattice planes, in a periodic fashion, it is possible to accommodate additional misfit beyond perfect domain matching. Thus, we can potentially design epitaxial growth of films with any lattice misfit on a given substrate with atomically clean surfaces. In situ x-ray diffraction studies on initial stages of growth of ZnO films on sapphire correctly identify a compressive stress and a rapid relaxation within 1 to 2 monolayers, consistent with the DME framework and the fact that the critical thickness is less than 1 monolayer. DME examples ranging from the Ge–Si/Si(100) system with 49/50 matching (2% strain) to metal/Si systems with 1/2 matching (50% strain) are tabulated, strategies for growing strain-free films by engineering the misfit to be confined near the interface are presented, and the potential for epitaxial growth of films with any lattice misfit on a given substrate with atomically clean surfaces is discussed. DA - 2003/1/1/ PY - 2003/1/1/ DO - 10.1063/1.1528301 VL - 93 IS - 1 SP - 278-285 SN - 1089-7550 ER -