TY - JOUR TI - Interfacial Solute-Atom Segregation: An Atomic-scale Ahenomenon with Implications for the Oxidation Kinetics of Pt-Al Alloys AU - Dickey, EC AU - Alexander, KB AU - Pint, BA T2 - Microscopy and Microanalysis AB - Interfacial solute-atom segregation is known to have profound effects on macroscopic physical properties (e.g. electronic transport or fracture toughness) in interface-influenced or controlled materials. It has recently been shown that solute-atom segregation also can play an influential role in the dynamics of phase transformations, in particular the oxidation kinetics of alumina-forming alloys such as PtAl. By coupling analytical electron microscopy (AEM) with conventional macroscopic oxidation studies, we have demonstrated that oxidation kinetics are affected by atomic-scale segregation of dopant species to the grain boundaries and metal-oxide boundaries in the system. Furthermore, these studies illustrate the utility of AEM techniques in elucidating the atomic-scale aspects of macroscopic physical phenomena such as phase transformations. Oxidation studies were carried out on PtAl alloys with and without small additions of Zr to the alloy. While the pure PtAl alloys exhibited oxide scale spallation and very fast oxidation rates, the Zrcontaining alloys maintained a well-adhered oxide scale and significantly lower oxidation rates. DA - 1998/7/1/ PY - 1998/7/1/ DO - 10.1017/S1431927600023977 VL - 4 IS - 2 S SP - 770-771 UR - https://app.dimensions.ai/details/publication/pub.1129043725 ER - TY - CHAP TI - Thin film transistors fabricated with poly-Si films crystallized by microwave annealing AU - Choi, YW AU - Lee, JN AU - Jang, TW AU - Ahn, B AU - Parsons, GN AU - Tsai, CC AU - Fahlen, TS AU - Seager, CH T2 - Flat-Panel Display Materials-1998 PY - 1998/// VL - 508 SP - 139-144 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000077248500021&KeyUID=WOS:000077248500021 ER - TY - CHAP TI - Synthesis and characterization of luminescent ZnO powders produced by thermally-induced doping AU - Allieri, B AU - Depero, LE AU - Sangaletti, L AU - Antonini, L AU - Bettinelli, M AU - Parsons, GN AU - Tsai, CC AU - Fahlen, TS AU - Seager, CH T2 - Flat-Panel Display Materials-1998 PY - 1998/// VL - 508 SP - 275-280 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000077248500042&KeyUID=WOS:000077248500042 ER - TY - CHAP TI - Reaction processes for low temperature (< 150 degrees C) plasma enhanced deposition of hydrogenated amorphous silicon thin film transistors on transparent plastic substrates AU - Parsons, GN AU - Yang, CS AU - Klein, TM AU - Smith, L AU - Tsai, CC AU - Fahlen, TS AU - Seager, CH T2 - Flat-Panel Display Materials-1998 PY - 1998/// VL - 508 SP - 19-24 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000077248500003&KeyUID=WOS:000077248500003 ER - TY - JOUR TI - Reaction processes for low temperature (< 150 degrees C) plasma enhanced deposition of hydrogenated amorphous silicon thin film transistors on transparent plastic substrates AU - Parsons, GN AU - Yang, CS AU - Klein, TM AU - Smith, L AU - Schropp, R AU - Branz, HM AU - Hack, M AU - Shimizu, I AU - Wagner, S T2 - Amorphous and Microcrystalline Silicon Technology-1998 DA - 1998/// PY - 1998/// VL - 507 SP - 19-24 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000079335700003&KeyUID=WOS:000079335700003 ER - TY - CHAP TI - High conductivity gate metallurgy for TFT/LCD's AU - Fryer, PM AU - Colgan, E AU - Galligan, E AU - Graham, W AU - Horton, R AU - Jenkins, L AU - John, R AU - Kuo, Y AU - Latzko, K AU - Libsch, F AU - Lien, A AU - Nywening, R AU - Polastre, R AU - Rothwell, ME AU - Wilson, J AU - Wisnieff, R AU - Wright, S AU - Parsons, GN AU - Tsai, CC AU - Fahlen, TS AU - Seager, CH T2 - Flat-Panel Display Materials-1998 PY - 1998/// VL - 508 SP - 37-46 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000077248500006&KeyUID=WOS:000077248500006 ER - TY - CONF TI - A remotely interrogatable magnetochemical sensor for environmental monitoring AU - Grimes, CA AU - Stoyanov, P AU - Seitz, WR AU - Doherty, SA AU - Dickey, EC C2 - 1998/// C3 - 1998 IEEE AEROSPACE CONFERENCE PROCEEDINGS, VOL 5 DA - 1998/// SP - 87-92 ER - TY - CONF TI - Towards (predictive) structure-property relationships for heterophase interfaces in oxides AU - Dravid, VP AU - Dickey, EC AU - Revcolevschi, A C2 - 1998/// C3 - BOUNDARIES & INTERFACES IN MATERIALS: THE DAVID A. SMITH SYMPOSIUM DA - 1998/// SP - 169-177 ER - TY - JOUR TI - Dislocations at ductile/plastic crack tips: In-situ TEM observations AU - Jagannadham, K. T2 - Materials Research Innovations AB - In-situ observations of dislocation structures ahead of crack tips in TEM metal foils are reviewed. Two cases are compared in particular: Structure development during in-situ straining to failure of (i) electron-transparent foils ahead of the tip of a growing crack that spreads from the thinnest regions or perforations and (ii) initially non-transparent thick foils. In the latter case cracks formed only after substantial in-situ straining, and they propagated along dislocation cell walls via repeated stimulated crack nucleation ahead of the tip. This behavior was shown to adequately simulate bulk behavior and such cracks do not exhibit dislocation-free zones at their tips. By contrast, dislocation-free regions along ligaments formed by crack propagation and observed in thin (e.g. about 100 nm or less) TEM foils are found to be artifacts due to strong dislocation image forces. These image forces at the same time limit mutual dislocation interactions to the thickness of the foil, and rotate the dislocations to be normal to the foil plane, meanwhile straightening them. This behavior has no correspondence to conditions at real cracks in bulk materials. Theoretical expressions are derived for the dislocation densities ahead of crack tips that give rise to long-range and shorter range stress fields in mode I crack tip configurations, respectively. DA - 1998/// PY - 1998/// DO - 10.1007/s100190050050 VL - 1 IS - 4 SP - 254-264 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-24044483938&partnerID=MN8TOARS KW - cracks KW - in-situ straining KW - dislocations KW - crack tips KW - dislocation-free zones ER - TY - JOUR TI - Multilayer diamond heat spreaders for electronic power devices AU - Jagannadham, K. T2 - Solid-State Electronics AB - Single layer diamond and multilayer diamond heat spreader substrates are prepared and bonded to device wafers of silicon and gallium arsenide. Metallization schemes for the diamond surface and the backside of the device wafers are described. Bonding of the device wafers to the diamond substrates using the high thermal conductivity gold–tin eutectic solder is carried out. Characterization of the bond for the distribution of different elements in the metallization layers and the solder, for the presence of microscopic defects such as voids and cracks, for the adhesion strength and for the stability of the bond under thermal cycling is performed. The heat spreader characteristics of the substrates with single and multlayer diamond are determined using infrared imaging of the bonded device wafers and compared with that of wafers bonded to metal substrates. Modeling and analysis of the effectivethermal conductivity showed that the multilayer diamond substrates are better heat spreaders and reduce the device temperature so that the life of the electronic devices is prolonged. DA - 1998/// PY - 1998/// DO - 10.1016/S0038-1101(98)00216-0 VL - 42 IS - 12 SP - 2199-2208 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0032304412&partnerID=MN8TOARS ER - TY - CONF TI - Superhard biocompatible coatings AU - Narayan, R.J. AU - Wei, Q. AU - Sharma, A.K. AU - Jagannadham, K. AU - Narayan, J. C2 - 1998/// C3 - TMS Annual Meeting DA - 1998/// SP - 301-308 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0031710366&partnerID=MN8TOARS ER - TY - CONF TI - Comparison of AlN films synthesized by pulsed laser ablation and magnetron sputtering techniques AU - Jagannadham, K. AU - Sharma, A.K. AU - Wei, Q. AU - Kalyanraman, R. AU - Narayan, J. C2 - 1998/// C3 - Materials Research Society Symposium - Proceedings DA - 1998/// VL - 505 SP - 469-474 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0031629667&partnerID=MN8TOARS ER - TY - CONF TI - Comparative study of residual stresses in single and multilayer composite diamond coatings AU - Jagannadham, K. AU - Watkins, T.R. C2 - 1998/// C3 - Materials Research Society Symposium - Proceedings DA - 1998/// VL - 505 SP - 391-396 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0031621445&partnerID=MN8TOARS ER - TY - CONF TI - Atomic structure and property correlation in pulsed laser deposited high-Tc films AU - Kalyanaraman, R. AU - Oktyabrsky, S. AU - Jagannadham, K. AU - Narayan, J. C2 - 1998/// C3 - Materials Research Society Symposium - Proceedings DA - 1998/// VL - 526 SP - 281-286 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0032316887&partnerID=MN8TOARS ER - TY - JOUR TI - Variation of oxygen content and crystal chemistry of YBa4Cu3O8.5+delta AU - ZHU, YT AU - BALDONADO, PS AU - PETERSON, EJ AU - al., T2 - PHYSICA C DA - 1998/// PY - 1998/// VL - 298 IS - 1-2 SP - 29-36 ER - TY - JOUR TI - Synthesis and characterization of the new compound EuBa4Cu3O8.5+delta AU - ZHU, YT AU - PETERSON, EJ AU - BALDONADO, PS AU - al., T2 - JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS DA - 1998/// PY - 1998/// VL - 59 IS - 8 SP - 1331-1336 ER - TY - JOUR TI - Severe plastic deformation: new technique for powder consolidation and grain size refinement AU - ALEXANDROV, , IV AU - ZHU, YT AU - LOWE, TC AU - al., T2 - POWDER METALLURGY DA - 1998/// PY - 1998/// VL - 41 IS - 1 SP - 11-13 ER - TY - JOUR TI - Microstructures and properties of nanocomposites obtained through SPTS consolidation of powders AU - ALEXANDROV, , IV AU - ZHU, YT AU - LOWE, TC AU - al., T2 - METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE DA - 1998/// PY - 1998/// VL - 29 IS - 9 SP - 2253-2260 ER - TY - JOUR TI - Kinetics of thermal, passive oxidation of Nicalon fibers AU - ZHU, YT AU - TAYLOR, ST AU - STOUT, MG AU - al., T2 - JOURNAL OF THE AMERICAN CERAMIC SOCIETY DA - 1998/// PY - 1998/// VL - 81 IS - 3 SP - 655-660 ER - TY - BOOK TI - Influence of reinforcement morphology on the mechanical properties of short-fiber composites AU - Zhu, YT AU - Valdez, JA AU - Shi, N AU - Lovato, ML AU - Stout, MG AU - Zhou, SJ AU - Blumenthal, WR AU - Lowe, TC DA - 1998/// PY - 1998/// PB - SE - 251-259 ER - TY - JOUR TI - Evaluation of a modified Weibull distribution for describing the strength of ceramic fibers and whiskers with varying diameters AU - ZHU, YT AU - BUTT, DP AU - TAYLOR, ST AU - al., T2 - JOURNAL OF TESTING AND EVALUATION DA - 1998/// PY - 1998/// VL - 26 IS - 2 SP - 144-150 ER - TY - JOUR TI - Crystal structure and chemistry of four new RBa4Cu3O8.5+delta (R = Ho, Er, Tm and Yb) compounds AU - ZHU, YT AU - PETERSON, EJ AU - BALDONADO, PS AU - al., T2 - JOURNAL OF ALLOYS AND COMPOUNDS DA - 1998/// PY - 1998/// VL - 281 IS - 2 SP - 137-145 ER - TY - JOUR TI - Consolidation of nanometer sized powders using severe plastic torsional straining AU - ALEXANDROV, , IV AU - ZHU, YT AU - LOWE, TC AU - al., T2 - NANOSTRUCTURED MATERIALS DA - 1998/// PY - 1998/// VL - 10 IS - 1 SP - 45-54 ER - TY - JOUR TI - Characterization of Nicalon fibres with varying diameters - Part II - Modified Weibull distribution AU - ZHU, YT AU - TAYLOR, ST AU - STOUT, MG AU - al., T2 - JOURNAL OF MATERIALS SCIENCE DA - 1998/// PY - 1998/// VL - 33 IS - 6 SP - 1475-1480 ER - TY - JOUR TI - Characterization of Nicalon fibres with varying diameters - Part I - Strength and fracture studies AU - TAYLOR, ST AU - ZHU, YT AU - BLUMENTHAL, WR AU - al., T2 - JOURNAL OF MATERIALS SCIENCE DA - 1998/// PY - 1998/// VL - 33 IS - 6 SP - 1465-1473 ER - TY - JOUR TI - A composite reinforced with bone-shaped short fibers AU - ZHU, YT AU - VALDEZ, JA AU - SHI, N AU - al., T2 - SCRIPTA MATERIALIA DA - 1998/// PY - 1998/// VL - 38 IS - 9 SP - 1321-1325 ER - TY - BOOK TI - Towards (predictive) structure-property relationships for heterophase interfaces in oxides AU - Dravid, VP AU - Dickey, EC AU - Revcolevschi, A DA - 1998/// PY - 1998/// PB - SE - 169-177 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000072465300020&KeyUID=WOS:000072465300020 ER - TY - JOUR TI - Three-dimensional atomic structure of NiO-ZrO2(cubic) interfaces AU - Dickey, EC AU - Dravid, VP AU - Nellist, PD AU - Wallis, DJ AU - Pennycook, SJ T2 - Acta Materialia AB - The three-dimensional atomic structure of low-energy NiO–ZrO2(cubic) interfaces is determined through a combination of electron imaging and spectroscopy techniques. High resolution electron microscopy, and Z-contrast STEM imaging with simultaneous electron energy loss spectroscopy are employed as complementary techniques for elucidating the structural and chemical aspects of the interface and associated interfacial relaxation mechaubic) interface. The planar interfaces show an atomically abrupt transition between the two phases which share a common oxygen plane at the boundary. Structural relaxations accommodating the lattice mismatch indicate that the boundary has relaxed to a low-energy configuration. The resulting interface structure is found to facilitate strong bonding across the boundary as is reflected in the fracture behavior of the composite system. DA - 1998/// PY - 1998/// DO - 10.1016/S1359-6454(97)00373-X VL - 46 IS - 5 SP - 1801-1816 UR - https://app.dimensions.ai/details/publication/pub.1028274840 ER - TY - JOUR TI - Reversible intercalation of charged iodine chains into carbon nanotube ropes AU - Grigorian, L AU - Williams, KA AU - Fang, S AU - Sumanasekera, GU AU - Loper, AL AU - Dickey, EC AU - Pennycook, SJ AU - Eklund, PC T2 - Physical Review Letters AB - We report intercalation of charged polyiodide chains into the interstitial channels in a single-wall carbon nanotube (SWNT) rope lattice, suggesting a new carbon chemistry for nanotubes, distinctly different from that of graphite and ${\mathrm{C}}_{60}$. This structural model is supported by results from Raman spectroscopy, x-ray diffraction, $Z$-contrast electron microscopy, and electrical transport data. Iodine-doped SWNTs are found to be air stable, permitting the use of a variety of techniques to explore the effect of charge transfer on the physical properties of these novel quantum wires. DA - 1998/// PY - 1998/// DO - 10.1103/PhysRevLett.80.5560 VL - 80 IS - 25 SP - 5560-5563 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000074313000025&KeyUID=WOS:000074313000025 ER - TY - JOUR TI - Chemical attachment of organic functional groups to single-walled carbon nanotube material AU - Chen, Y AU - Haddon, RC AU - Fang, S AU - Rao, AM AU - Lee, WH AU - Dickey, EC AU - Grulke, EA AU - Pendergrass, JC AU - Chavan, A AU - Haley, BE AU - Smalley, RE T2 - Journal of Materials Research DA - 1998/// PY - 1998/// DO - 10.1557/JMR.1998.0337 VL - 13 IS - 9 SP - 2423-2431 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000075621600011&KeyUID=WOS:000075621600011 ER - TY - BOOK TI - A remotely interrogatable magnetochemical sensor for environmental monitoring AU - Grimes, CA AU - Stoyanov, P AU - Seitz, WR AU - Doherty, SA AU - Dickey, EC DA - 1998/// PY - 1998/// PB - SE - 87-92 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000074665200008&KeyUID=WOS:000074665200008 ER - TY - JOUR TI - In-situ mass spectrometry for real-time uniformity sensing in ECR silicon dioxide etching AU - Chambers, J.J. AU - Min, K. AU - Parsons, G.N. T2 - Journal of Vacuum Science & Technology DA - 1998/// PY - 1998/// VL - B IS - 16 SP - 2996-3002 ER - TY - PAT TI - Modulated-structure of PZT/PT ferroelectric thin films for non-volatile random access memories AU - Varsheny, U. AU - Kingon, A. I. C2 - 1998/// DA - 1998/// PY - 1998/// ER - TY - PAT TI - Thin film optical measurement system and method with calibrating ellipsometer AU - Aspnes, D. E. AU - Opsal, J. AU - Faton, J. T. C2 - 1998/// DA - 1998/// PY - 1998/// ER - TY - JOUR TI - On velocity discontinuities in elastoplastic bicrystals in channel die compression AU - Havner, KS T2 - INTERNATIONAL JOURNAL OF PLASTICITY AB - Possible consequences of including lattice straining in f.c.c. bicrystal models in channel die compression are investigated. It is determined that the tangential velocity discontinuities which emanate from the interface edges in rigid/plastic models are not eliminated by taking crystal elasticity into account. DA - 1998/// PY - 1998/// DO - 10.1016/S0749-6419(97)00040-5 VL - 14 IS - 1-3 SP - 61-74 SN - 0749-6419 ER - TY - JOUR TI - On the stress state at the yield point in symmetric bicrystals in (110) channel die compression AU - Havner, KS AU - Yu, PG T2 - MECHANICS OF MATERIALS AB - The stress state at the yield point in symmetric fcc bicrystals is analytically investigated for a range of crystal lattice orientations in (110) channel die compression. Although strain-rates and lattice-rotation rates necessarily are nonuniform, it is proved that the stress field satisfying both equilibrium and yield-locus constraints must lie on an edge of the locus and is thereby uniform. DA - 1998/4// PY - 1998/4// DO - 10.1016/S0167-6636(97)00049-5 VL - 27 IS - 4 SP - 211-227 SN - 0167-6636 KW - crystal plasticity KW - bicrystal KW - channel die compression KW - multiple slip KW - stress analysis KW - yield-point state ER - TY - CONF TI - Microstructure and IR range optical properties of pure DLC and DLC containing dopants prepared by pulsed laser deposition AU - Wei, Q. AU - Sharma, A. K. AU - Narayan, R. J. AU - Ravindra, N. M. AU - Oktyabrsky, S. AU - Sankar, J. AU - Muth, J. F. AU - Kolbas, R. M. AU - Narayan, J. C2 - 1998/// C3 - Advances in laser ablation of materials: Symposium held April 13-16, 1998, San Francisco, California, U.S.A. (Materials Research Society symposia proceedings ; v. 526). CN - TA1715 .A38 1998 DA - 1998/// SP - 331 PB - Warrendale, Pa.: Materials Research Society ER - TY - CONF TI - Growth of high quality single crystal ZnO films on sapphire by pulsed laser ablation AU - Sharma, A. K. AU - Dovidenko, K. AU - Oktyabrsky, S. AU - Moxey, D. E. AU - Muth, J. F. AU - Kolbas, R. M. AU - Narayan, J. C2 - 1998/// C3 - Advances in laser ablation of materials: Symposium held April 13-16, 1998, San Francisco, California, U.S.A. (Materials Research Society symposia proceedings ; v. 526). CN - TA1715 .A38 1998 DA - 1998/// SP - 305 PB - Warrendale, Pa.: Materials Research Society ER - TY - CONF TI - Germanium nanostructures fabricated by pulsed laser deposition AU - Hassan, K. M. AU - Sharma, A. K. AU - Narayan, J. AU - Muth, J. F. AU - Teng, C. W. AU - Kolbas, R. M. C2 - 1998/// C3 - Microcrystalline and nanocrystalline semiconductors--1998: symposium held November 30-December 3, 1998, Boston, Massachusetts, U.S.A. CN - TK7871.85 .M534 1999 DA - 1998/// ER - TY - JOUR TI - Diffusion of iron in the silicon dioxide layer of silicon-on-insulator structures AU - Kononchuk, O AU - Korablev, KG AU - Yarykin, N AU - Rozgonyi, GA T2 - APPLIED PHYSICS LETTERS AB - The redistribution of iron implanted into the oxide layer of silicon-on-insulator structures has been measured using the secondary ion mass spectroscopy technique after annealing at 900–1050 °C. Iron diffusion has been found to be much faster in the oxide prepared by the separation-byimplantation-of-oxygen (SIMOX) procedure compared to the thermally grown oxide in the bonded and etched-back structures. In the latter case, the Fe diffusivity exhibits a thermal activation with an energy of 2.8 eV, confirming the literature data on silica glass. In the SIMOX oxide, the diffusivity depends only weakly on temperature, indicative of an essentially activation-free diffusion mechanism. Gettering of Fe at below-the-buried-oxide defects in SIMOX wafers has been observed. No iron segregation has been detected at the SiO2–Si interfaces. DA - 1998/8// PY - 1998/8// DO - 10.1063/1.122128 VL - 73 IS - 9 SP - 1206-1208 SN - 0003-6951 ER - TY - JOUR TI - Materials properties and characterization of SiC AU - Jarrendahl, K AU - Davis, RF T2 - SIC MATERIALS AND DEVICES AB - This chapter discusses the materials properties and characterization of silicon carbide (Sic). Wide energy bandgaps, high thermal conductivity, high-saturated electron drift velocities, and high-breakdown electric fields make Sic a candidate of choice for high-temperature, high-speed, high-frequency, and high-power applications. In a polytypic compound, similar sheets of atoms or symmetrical variants are stacked atop each other and related according to a symmetry operator. The most stable way to stack an identical second sheet of close-packed spheres is to place the spheres atop the valleys in the first sheet. The Sic polytypes can be n-type doped using nitrogen or phosphorus as donors and p-type using boron, aluminum, or gallium as acceptors. In general, unintentionally doped Sic has n-type conductivity because of nitrogen donors included as a contaminant during the production of the material. The electron and hole mobilities in Sic are a function of the nature of the material (carrier concentration, polytype, structural quality) and temperature. DA - 1998/// PY - 1998/// DO - 10.1016/S0080-8784(08)62843-4 VL - 52 SP - 1-20 SN - 0080-8784 ER - TY - CONF TI - The behavior of SIMCON under ballistic loading: An analytical study AU - Schwarz, O. J. AU - Horie, Y. AU - Krstulovic-Opara, N. C2 - 1998/// C3 - Engineering mechanics: Proceedings of the 12th ASCE Engineering Mechanics Conference: A Force for the 21st Century, La Jolla, CA, May 17-20, 1998 DA - 1998/// M1 - 1998 ER - TY - JOUR TI - Silicon epitaxy on Si(100) with adsorbed oxygen AU - Tsu, R. AU - Filios, A. AU - Lofgren, C. AU - Dovidenko, K. AU - Wang, C. G. T2 - Electrochemical and Solid State Letters DA - 1998/// PY - 1998/// VL - 1 IS - 2 SP - 80-82 ER - TY - JOUR TI - Broadband spectral operation of a rotating-compensator ellipsometer AU - Opsal, J AU - Fanton, J AU - Chen, J AU - Leng, J AU - Wei, L AU - Uhrich, C AU - Senko, M AU - Zaiser, C AU - Aspnes, DE T2 - THIN SOLID FILMS AB - We show that a rotating-compensator ellipsometer (RCE) with a zero-order retarder can be used for broadband spectroscopy, for example from 200 to 800 nm, when the compensator retardation δ is known as a function of wavelength and sample properties are determined by least-squares methods. The resulting instrument offers the standard advantages of an RCE and is no less sensitive than a rotating-analyzer or -polarizer ellipsometer under worst-case conditions, where the sin (2ωt) component vanishes at δ=180°C. Sensitivity and operation are illustrated by application to the measurement of crystalline Si. DA - 1998/2// PY - 1998/2// DO - 10.1016/S0040-6090(97)00769-4 VL - 313 IS - 1998 SP - 58-61 SN - 0040-6090 KW - rotating-compensator ellipsometer (RCE) KW - least-squares analysis KW - pseudodielectric function KW - crystalline Si ER - TY - JOUR TI - Analytic representations of the dielectric functions of crystalline and amorphous Si and crystalline Ge for very large scale integrated device and structural modeling AU - Leng, J AU - Opsal, J AU - Chu, H AU - Senko, M AU - Aspnes, DE T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS AB - Various representations of the dielectric functions of semiconducting materials have been proposed. We compare five different models for representing the dielectric functions of crystalline (c-) Si, amorphous (a-) Si, and c-Ge from 1.5 to 6.0 eV. The four-oscillator critical point with parity plus one-dimensional tight-binding model (CPP-1D) best represents c-Si. Different models best represent a-Si and c-Ge. These representations provided a basis for modeling variations encountered in semiconductor manufacturing. DA - 1998/// PY - 1998/// DO - 10.1116/1.581137 VL - 16 IS - 3 SP - 1654-1657 SN - 0734-2101 ER - TY - CONF TI - Thermal expansion of GaN and AlN AU - Wang, K. AU - Reeber, R. R. C2 - 1998/// C3 - Nitride semiconductors: Symposium held December 1-5, 1997, Boston, Massachusetts, U.S.A. (Materials Research Society Symposium proceedings; v. 482). CN - TK7871.15 .N57 N57 1998 DA - 1998/// SP - 863-868 PB - Warrendale, Pa.: Materials Research Society, 1998. ER - TY - JOUR TI - The temperature dependence of the conductivity of silicone oil and related electrorheology of suspensions containing zeolite particles AU - Wu, CW AU - Conrad, H T2 - JOURNAL OF PHYSICS D-APPLIED PHYSICS AB - The effect of temperature (22-) on the conductivity of silicone oil was determined employing three heating-cooling schedules. In all cases the conductivity was super-ohmic with a good fit to the equation based on Onsager's dissociation theory, namely DA - 1998/12/7/ PY - 1998/12/7/ DO - 10.1088/0022-3727/31/23/015 VL - 31 IS - 23 SP - 3403-3409 SN - 0022-3727 ER - TY - JOUR TI - Simulation of a vertical reactor for high pressure organometallic chemical vapor deposition AU - Kepler, GM AU - Hopfner, C AU - Scroggs, JS AU - Bachmann, KJ T2 - MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY AB - The suitability of a vertical cylindrical reactor with highly constrained radial flow from a central gas injection port past a set of heated substrate wafers that are embedded in the top channel wall has been evaluated in the context of organometallic chemical vapor deposition (OMCVD) at elevated pressure. Numerical simulations showed that, in addition to the limitation on the channel height necessary for preventing buoyancy driven recirculation, negotiating the ninety-degree bend at the inlet is problematic and also constrains the channel height below a critical value, at which the radial flow area after the inlet bend is equal to the cross-sectional area of the central gas injection port. Restricting the channel height poses the danger of heating of the channel wall opposite to the substrate wafers causing potential problems with deposition of decomposition products and competitive polycrystalline film growth at this location. These problems can be avoided by actively cooling the channel wall opposite to the substrate and by keeping the retention time of the source vapor molecules and fragments thereof in the wafer location below a critical value. DA - 1998/12/4/ PY - 1998/12/4/ DO - 10.1016/s0921-5107(98)00256-6 VL - 57 IS - 1 SP - 9-17 SN - 0921-5107 KW - organometallic chemical vapor deposition KW - above-atmosphere pressure KW - numerical simulation KW - vertical reactor KW - compressible flow ER - TY - JOUR TI - Mechanical properties in tension of mechanically attrited nanocrystalline iron by the use of the miniaturized disk bend test AU - Malow, TR AU - Koch, CC T2 - ACTA MATERIALIA AB - The mechanical properties of warm compacted nanocrystalline (nc) iron powder compacts of near theoretical density in the grain size range between 8 and 33 nm were investigated. The elastic and plastic behavior were characterized by miniaturized disk bend tests and hardness measurements. Light and scanning electron microscopy (SEM) were used to document the deformation and fracture morphologies. The Young's modulus of the nc Fe was essentially the same as that of coarse grained Fe. All samples failed in a macroscopically brittle manner. Local plasticity in shear bands was observed in the samples with the larger grain sizes (>20 nm). An increasing failure stress with increasing grain size is probably due to a processing effect on the flaw controlled failure of the samples. The results are discussed in the context of the deformation and fracture behavior of micrometer grain size metals and alloys. DA - 1998/11/20/ PY - 1998/11/20/ DO - 10.1016/S1359-6454(98)00294-8 VL - 46 IS - 18 SP - 6459-6473 SN - 1359-6454 ER - TY - JOUR TI - Many-body and correlation effects in surface and interface spectra of optically absorbing materials AU - Aspnes, D. E. AU - Mantese, L. AU - Bell, K. A. AU - Rossow, U. T2 - Physica Status Solidi. A, Applications and Materials Science DA - 1998/// PY - 1998/// VL - 170 IS - 2 SP - 199-210 ER - TY - JOUR TI - Characterization of electron emitting surfaces of diamond and III-V nitrides AU - Nemanich, R. J. AU - Baumann, P. K. AU - Benjamin, M. C. AU - English, S. L. AU - Hartman, J. D. AU - Sowers, A. T. AU - Ward, B. L. T2 - Diamond Films and Technology DA - 1998/// PY - 1998/// VL - 8 IS - 4 SP - 211-223 ER - TY - JOUR TI - Analytic representations of the dielectric functions of materials for device and structural modeling AU - Leng, J AU - Opsal, J AU - Chu, H AU - Senko, M AU - Aspnes, DE T2 - THIN SOLID FILMS AB - Analytic representations of the dielectric function ε are needed for the analysis of optical data of complex materials and structures. Here, we examine various harmonic-oscillator-based representations of the dielectric functions of the silicon-related materials, crystalline Si, amorphous Si, and silicon nitride. For crystalline semiconductors we develop a new representation with a prefactor proportional to ω−2, the expected response for materials with wavefunctions that are eigenfunctions of the momentum operator. DA - 1998/2// PY - 1998/2// DO - 10.1016/S0040-6090(97)00799-2 VL - 313 IS - 1998 SP - 132-136 SN - 0040-6090 KW - analytic representations KW - dielectric functions KW - crystalline Si KW - amorphous Si KW - silicon nitride ER - TY - JOUR TI - Trends in residual stress for GaN/AlN/6H-SiC heterostructures AU - Edwards, NV AU - Bremser, MD AU - Davis, RF AU - Batchelor, AD AU - Yoo, SD AU - Karan, CF AU - Aspnes, DE T2 - APPLIED PHYSICS LETTERS AB - We discuss trends in residual stress as a function of film thickness, growth temperature, and substrate orientation for GaN/AlN/6H–SiC heterostructures. Films are mostly compressive for samples less than about 0.7 μm thick, are tensile up to about 2 μm, then abruptly become less tensile with stress values near 1 kbar thereafter. We interpret this as a successive relief of lattice mismatch and thermal stresses culminating in a catastrophic relief by unknown mechanisms at moderate thicknesses. These data indicate that relaxation processes in these heterostructures are not as well understood as previously supposed. DA - 1998/11/8/ PY - 1998/11/8/ DO - 10.1063/1.122597 VL - 73 IS - 19 SP - 2808-2810 SN - 1077-3118 ER - TY - JOUR TI - Thermally induced imprint properties of chemical solution derived PLZT thin films AU - Kim, S. H. AU - Kim, D. J. AU - Hong, J. G. AU - Streiffer, S. K. AU - Kingon, A. I. T2 - Integrated Ferroelectrics DA - 1998/// PY - 1998/// VL - 22 IS - 1-4 SP - 653-662 ER - TY - JOUR TI - The influence of nitrogen addition on the morphology, growth rate, and Raman spectra of combustion grown diamond AU - Wolden, CA AU - Draper, CE AU - Sitar, Z AU - Prater, JT T2 - DIAMOND AND RELATED MATERIALS AB - The influence of intentional nitrogen addition on diamond deposition using a low pressure acetylene–oxygen flat flame was studied. The film morphology was assessed by scanning electron microscopy, growth rates by cross-section thickness measurements, and nitrogen incorporation by Raman spectroscopy. It was found that the addition of nitrogen increased the growth parameter α, and for the conditions investigated 〈100〉 textured films were obtained for nitrogen levels between three and five parts per thousand (ppt). It was found that there was no change in growth rate over the range 0–7 ppt N2 addition. At higher levels the films became amorphous. For low levels (<5 ppt) the luminescence signal in the Raman spectra increased steadily with nitrogen addition, while the features associated with sp2 and sp3 bonded carbon were unchanged. Comparisons with natural diamond and hot-filament grown material demonstrate that nitrogen is a significant impurity in our acetylene source. Equilibrium calculations showed that NO and atomic nitrogen were the two dominant products that may be responsible for the observed changes in morphology and Raman spectra. DA - 1998/8// PY - 1998/8// DO - 10.1016/S0925-9635(98)00172-1 VL - 7 IS - 8 SP - 1178-1183 SN - 0925-9635 KW - nitrogen KW - combustion synthesis KW - texture KW - Raman ER - TY - BOOK TI - The image processing handbook AU - Russ, J. C. CN - TA1637 .R87 1998 DA - 1998/// PY - 1998/// PB - Boca Raton, FL: CRC Press SN - 0849325323 ER - TY - JOUR TI - Structural and electronic properties of boron nitride thin films containing silicon AU - Ronning, C AU - Banks, AD AU - McCarson, BL AU - Schlesser, R AU - Sitar, Z AU - Davis, RF AU - Ward, BL AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - The incorporation of silicon into boron nitride films (BN:Si) has been achieved during ion beam assisted deposition growth. A gradual change from cubic boron nitride (c-BN) to hexagonal boron nitride (h-BN) was observed with increasing silicon concentration. Ultraviolet photoelectron spectroscopy, field emission, and field emission electron energy distribution experiments indicated that the observed electron transport and emission were due to hopping conduction between localized states in a band at the Fermi level for the undoped c-BN films and at the band tails of the valence band maximum for the BN:Si films. A negative electron affinity was observed for undoped c-BN films; this phenomenon disappeared upon silicon doping due to the transformation to h-BN. No shift of the Fermi level was observed in any BN:Si film; thus, n-type doping can be excluded. DA - 1998/11/1/ PY - 1998/11/1/ DO - 10.1063/1.368752 VL - 84 IS - 9 SP - 5046-5051 SN - 0021-8979 ER - TY - JOUR TI - Remote plasma-enhanced chemical vapor deposition of SiO2 using Ar/N2O and SiH4 AU - Courtney, CH AU - Smith, BC AU - Lamb, HH T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - Remote plasma‐enhanced chemical vapor deposition of using a radio‐frequency (rf) Ar/ plasma and downstream‐injected was investigated. The deposition rate at 20 W rf power was measured as a function of pressure, temperature, and flow rate. The deposition rate at 300°C and 300 mTorr depends linearly on the flow rate. The deposition rate is independent of flow rate for ratios much greater than 1, consistent with oxygen saturation of the growth surface. The deposition rate increases linearly with pressure up to 400 mTorr. A plateau in the deposition rate is observed above 400 mTorr, and is ascribed to the onset of parasitic gas‐phase reactions leading to particle formation. Negative apparent activation energies are observed at pressures ⩽400 mTorr, suggesting that adsorption of Si‐bearing species is the rate‐limiting step in deposition. The deposition chemistry was probed using real‐time quadrupole mass spectrometry (QMS) and optical emission spectroscopy (OES). The and QMS signal intensities increase monotonically with flow rate; approximately 0.67 moles of and 1.33 moles of are produced per mole of consumed. OES evidences the presence of Ar metastables, metastables, excited NO molecules, and atomic O in the plasma. Fourier transform infrared spectroscopy of thick films demonstrated that Si‐H and Si‐OH groups are present at very low concentrations (<1 atom %). Single‐wavelength ellipsometry indicated that films deposited under typical O‐rich conditions have an average refractive index of 1.464. DA - 1998/11// PY - 1998/11// DO - 10.1149/1.1838898 VL - 145 IS - 11 SP - 3957-3962 SN - 0013-4651 ER - TY - JOUR TI - Preferred orientation, phase formation and the electrical properties of pulsed laser deposited SrBi2Ta2O9 thin films AU - Fujimura, N AU - Thomas, DT AU - Streiffer, SK AU - Kingon, AJ T2 - JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS AB - Systematic studies on the preferred orientation, phase formation and the electrical properties of pulsed laser deposited SrBi 2 Ta 2 O 9 (SBT) have been performed. At a substrate temperature of 600°C, the film on SiO 2 was not crystallized. Above 650°C, very strong diffraction from a non-ferroelectric, (111)-oriented fluorite phase was obtained. Its crystallinity increased with increasing Bi content in the target. The fluorite phase was also observed in the film on Pt deposited below 600°C, which together with the pyrochlore phase resulted in the formation of an interfacial reaction product, Bi 2 Pt. Above 650°C, the films tend to grow as the perovskite SBT phase with a c -axis orientation which is not the polarization axis. In contrast, the formation of the fluorite and pyrochlore phases can be suppressed on Ir electrodes. DA - 1998/9// PY - 1998/9// DO - 10.1143/JJAP.37.5185 VL - 37 IS - 9B SP - 5185-5188 SN - 0021-4922 KW - SrBi2Ta2O9 KW - preferred orientation KW - ferroelectric properties KW - pyrochlore phase KW - fluorite phase ER - TY - JOUR TI - Interfacial modification as a route to novel bilayered morphologies in binary block copolymer/homopolymer blends AU - Laurer, JH AU - Smith, SD AU - Samseth, J AU - Mortensen, K AU - Spontak, RJ T2 - MACROMOLECULES AB - Addition of a relatively low-molecular-weight parent homopolymer to a lamellar AB diblock copolymer constitutes a reliable means by which to induce, in controllable fashion, transitions to other morphologies. In this study, we examine the effect of interfacial modification on such transitions in "extended" A(A/B)B copolymer/homopolymer blends in which (i) the A/B midblock fraction (relative to the copolymer molecular weight) is varied from 0.0 to 0.4 in 0.1 increments and (ii) the overall concentration of A ranges from 0.50 to 0.95. As this A/B fraction is increased at constant blend composition, the extent of homopolymer-induced lamellar swelling becomes measurably less pronounced, indicating that the A/B midblock serves to delocalize repulsion along the interphase separating adjacent lamellae. At higher homopolymer concentrations, an increase in the A/B fraction results in the formation of either unilamellar vesicles or a randomly connected bilayered membrane, rather than micelles. These membranes become unstable and transform to micelles at high copolymer dilution. The results presented here are discussed in terms of the complex morphologies observed in, and predicted for, low-molar-mass (co)surfactant systems. DA - 1998/7/28/ PY - 1998/7/28/ DO - 10.1021/ma980200j VL - 31 IS - 15 SP - 4975-4985 SN - 1520-5835 ER - TY - JOUR TI - Electrical properties of electrorheological particle clusters AU - Wu, CW AU - Conrad, H T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - The electrical conductivity of static clusters of ∼220-μm diameter humidified glass beads in silicone oil arranged in a rectangular or cubic lattice was determined under d.c. electric field. The current density flowing through the cluster increased with field strength. It was independent of the number of glass spheres forming a chain in the cluster but increased with the number of chains comprising the cluster. The conductivity of a single chain was about twice the saturation conductivity of the silicone oil. Some possible reasons for the enhanced current density of a cluster of particles compared to an equal number of single-row chains are proposed. DA - 1998/10/31/ PY - 1998/10/31/ DO - 10.1016/s0921-5093(98)00777-1 VL - 255 IS - 1-2 SP - 66-69 SN - 0921-5093 KW - electrorheology KW - glass beads KW - silicone oil KW - current density KW - conductivity KW - saturation zone KW - saturation field ER - TY - JOUR TI - Cleaning of AlN and GaN surfaces AU - King, SW AU - Barnak, JP AU - Bremser, MD AU - Tracy, KM AU - Ronning, C AU - Davis, RF AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - Successful ex situ and in situ cleaning procedures for AlN and GaN surfaces have been investigated and achieved. Exposure to HF and HCl solutions produced the lowest coverages of oxygen on AlN and GaN surfaces, respectively. However, significant amounts of residual F and Cl were detected. These halogens tie up dangling bonds at the nitride surfaces hindering reoxidation. The desorption of F required temperatures &gt;850 °C. Remote H plasma exposure was effective for removing halogens and hydrocarbons from the surfaces of both nitrides at 450 °C, but was not efficient for oxide removal. Annealing GaN in NH3 at 700–800 °C produced atomically clean as well as stoichiometric GaN surfaces. DA - 1998/11/1/ PY - 1998/11/1/ DO - 10.1063/1.368814 VL - 84 IS - 9 SP - 5248-5260 SN - 0021-8979 ER - TY - JOUR TI - Bicontinuous morphologies in homologous multiblock copolymers and their homopolymer blends AU - Laurer, JH AU - Hajduk, DK AU - Dreckotter, S AU - Smith, SD AU - Spontak, RJ T2 - MACROMOLECULES AB - ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTBicontinuous Morphologies in Homologous Multiblock Copolymers and Their Homopolymer BlendsJonathan H. Laurer, Damian A. Hajduk, Stefan Dreckötter, Steven D. Smith, and Richard J. SpontakView Author Information Departments of Materials Science & Engineering and Chemical Engineering, North Carolina State University, Raleigh, North Carolina 27695, Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, and Corporate Research Division, The Procter & Gamble Company, Cincinnati, Ohio 45239 Cite this: Macromolecules 1998, 31, 21, 7546–7549Publication Date (Web):October 2, 1998Publication History Received18 May 1998Revised17 August 1998Published online2 October 1998Published inissue 1 October 1998https://doi.org/10.1021/ma9807872Copyright © 1998 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views229Altmetric-Citations13LEARN 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. 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Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (140 KB) Get e-AlertsSUBJECTS:Conformation,Copolymers,Homopolymers,Morphology,X-ray scattering Get e-Alerts DA - 1998/10/20/ PY - 1998/10/20/ DO - 10.1021/ma9807872 VL - 31 IS - 21 SP - 7546-7549 SN - 0024-9297 ER - TY - JOUR TI - Tunneling currents through ultrathin oxide/nitride dual layer gate dielectrics for advanced microelectronic devices AU - Yang, HY AU - Niimi, H AU - Lucovsky, G T2 - JOURNAL OF APPLIED PHYSICS AB - Direct and Fowler–Nordheim tunneling currents through oxide and dual layer silicon oxide–silicon nitride dielectrics are investigated for substrate and gate injection. The calculations include depletion effects in the heavily doped (n+) polysilicon gate electrodes as well as quantization effects in the less heavily doped n-type substrates. The Wentzel–Kramers–Brillouin (WKB) effective mass approximation has been compared with exact calculations for the tunneling probability, and based on these comparisons it has been found that the WKB approximation is adequate for single layer dielectrics, but is not for the dual layer dielectrics that are the focus of this article. Using exact tunneling transmission calculations, current-voltage (I–V) characteristics for ultrathin single layer oxides with different thicknesses (1.4, 2.0, and 2.3 nm) have been shown to agree well with recently reported experiments. Extensions of this approach demonstrate that direct tunneling currents in oxide/nitride structures with oxide equivalent thickness of 1.5 and 2.0 nm can be significantly lower than through single layer oxides of the same respective thickness. DA - 1998/2/15/ PY - 1998/2/15/ DO - 10.1063/1.366976 VL - 83 IS - 4 SP - 2327-2337 SN - 0021-8979 ER - TY - JOUR TI - Transmission electron microscopy analysis of the oriented diamond growth on nickel substrates AU - Liu, W AU - Yang, PC AU - Wolden, CA AU - Davis, RF AU - Prater, JT AU - Sitar, Z T2 - JOURNAL OF APPLIED PHYSICS AB - Transmission electron microscopy (TEM) was used to investigate the interfacial microstructure and the phases that developed during the nucleation and growth of oriented diamond on Ni by a hot filament process. Oriented Ni4C nuclei were identified by plan-view TEM in a sample quenched during the nucleation stage. Likewise, the presence of the Ni4C phase between the diamond and the Ni substrate was observed by cross-section TEM in samples grown for several hours. The orientational relationship among the diamond, Ni4C, and Ni substrate was examined by selected area diffraction. Diamond and Ni4C interfacial phase had a good epitaxial relationship, while the interfacial Ni4C phase and the Ni substrate developed with a small misfit and rotation. Based on these experimental results, the nucleation mechanism of oriented diamond growth on Ni is proposed. DA - 1998/6/15/ PY - 1998/6/15/ DO - 10.1063/1.367885 VL - 83 IS - 12 SP - 7658-7663 SN - 0021-8979 ER - TY - JOUR TI - Surface cleaning, electronic states and electron affinity of diamond (100), (111) and (110) surfaces AU - Baumann, PK AU - Nemanich, RJ T2 - SURFACE SCIENCE AB - The effects of cleaning natural type IIb diamond (100), (111) and (110) samples by annealing and hydrogen – or deuterium plasma exposure were investigated by means of ultraviolet photoemission spectroscopy (UPS). Different wet chemical cleaning processes (a conventional chromic acid clean and an electrochemical etch) and a H plasma exposure have been employed to clean natural type IIb semiconducting diamond C(100) wafers. The effects of these processes on the diamond surface have been assessed and compared. As evidenced by Auger electron spectroscopy (AES), an oxygen free surface could be obtained following vacuum annealing to 900°C for the electrochemical process compared to 1050°C for the chromic acid etch. In addition, the technique of atomic force microscopy demonstrated the presence of oriented pits on the surface of samples that were electrochemically etched for long times at high currents. After a H plasma exposure the negative electron affinity (NEA) peak in the UPS spectra doubled in intensity. An anneal to 1100°C resulted in the removal of the sharp NEA feature. A second H plasma treatment resulted in the reappearance of the NEA peak similar to that after the first H plasma exposure. A (2×1) reconstructed low energy electron diffraction pattern was observed subsequent to the anneals as well as the H plasma treatments. The fact that a NEA can be induced or removed repeatedly by means of a H plasma exposure or annealing at 1100°C, respectively, provides evidence to correlate the appearance of a NEA with the presence of a monohydride terminated surface. Corresponding effects were found for (111) and (110) surfaces. A NEA could be induced by a H plasma and removed by annealing at 900 or 800°C for diamond (111) or (110) surfaces, respectively. Following a deuterium plasma exposure the diamond surfaces exhibited a NEA like the ones treated by a hydrogen plasma. Higher annealing temperatures were necessary to remove the NEA for deuterium due to the isotope effect. Values of 79 and 81 V μm−1 were measured for the field emission threshold of the oxygen terminated C(100) and C(110) surfaces, respectively. A value of 25 V μm−1 was determined for the hydrogen terminated C(110) surface. DA - 1998/7/1/ PY - 1998/7/1/ DO - 10.1016/S0039-6028(98)00259-3 VL - 409 IS - 2 SP - 320-335 SN - 0039-6028 KW - diamond KW - electron emission KW - field emission KW - photoemission KW - semiconductor surfaces KW - surface electronic phenomena KW - ultraviolet photoelectron spectroscopy ER - TY - JOUR TI - Secondary electron emission patterning of diamond with hydrogen and oxygen plasmas AU - Park, M AU - Choi, WB AU - Streiffer, SK AU - Hren, JJ AU - Cuomo, JJ T2 - APPLIED PHYSICS LETTERS AB - Secondary electron emission patterning of single crystal diamond surfaces with hydrogen and oxygen plasma treatments was demonstrated. Hydrogen plasma treated regions were much brighter than the oxygen terminated regions. Results of atomic force microscopy confirmed that the observed contrast is not topographical. Several other possible negative electron affinity (or low positive electron affinity) materials such as chemical vapor deposited (CVD) diamond, aluminum nitride, and tetrahedrally bonded amorphous carbon (txa−C1−x) were also investigated. Faint image contrast (patterning) was also observed from polycrystalline CVD diamond and polycrystalline aluminum nitride films; however, no contrast at all was obtained from tetrahedrally bonded amorphous carbon (txa−C1−x) films. DA - 1998/5/18/ PY - 1998/5/18/ DO - 10.1063/1.121424 VL - 72 IS - 20 SP - 2580-2582 SN - 0003-6951 ER - TY - JOUR TI - Phase coarsening and crack growth rate during thermo-mechanical cycling of 63Sn37Pb solder joints AU - Hacke, PL AU - Fahmy, Y AU - Conrad, H T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 1998/8// PY - 1998/8// DO - 10.1007/s11664-998-0125-0 VL - 27 IS - 8 SP - 941-947 SN - 0361-5235 KW - annealing KW - coarsening KW - fatigue crack growth rate KW - interphase diffusion KW - phase size KW - thermo-mechanical fatigue ER - TY - JOUR TI - Nondestructive determination of tensile properties and fracture toughness of cold worked A36 steel AU - Murty, KL AU - Mathew, MD AU - Wang, Y AU - Shah, VN AU - Haggag, FM T2 - INTERNATIONAL JOURNAL OF PRESSURE VESSELS AND PIPING AB - Tensile and fracture properties of ASTM grade A36 steel have been studied using nondestructive Stress–Strain Microprobe™ system (SSM), which is developed on the basis of automated ball indentation (ABI) technique. Tests have been carried out on as-received, and cold worked (4, 8 and 12%) materials at several temperatures in the range −150°C–+200°C at a constant strain rate. Tensile properties determined from ABI tests agreed well with the results from conventional tensile tests. The elastic–plastic fracture toughness parameter KJC was estimated from the ABI data. As expected, cold working resulted in increase in strength, decrease in fracture toughness and increase in ductile to brittle transition temperature. ABI is a reliable nondestructive technique for determining tensile and fracture properties of materials and has potential applications in the nuclear industry particularly to determine toughness degradation due to aging in service. DA - 1998/9// PY - 1998/9// DO - 10.1016/S0308-0161(98)00093-3 VL - 75 IS - 11 SP - 831-840 SN - 0308-0161 KW - cold worked A36 steel KW - fracture toughness KW - tensile properties KW - ball indentation ER - TY - JOUR TI - Multi-coated spheres: recommended electrorheological particles AU - Wu, CW AU - Conrad, H T2 - JOURNAL OF PHYSICS D-APPLIED PHYSICS AB - This paper considers the design of electrorheological (ER) particles. Multi-coated particles suspended in insulating (very weakly conducting) oil are recommended for obtaining high-performance ER suspensions. Only the outer two coatings determine the ER strength. The outermost coating should be a material with high dielectric constant, high electrical breakdown strength and a reasonable level of conductivity. The coating immediately below should be a highly conducting material. The inner coatings, including the core (which can be void), can be of any material having such a density that the composite particle has substantially the same density as the host liquid. Our analysis gives that multi-coated particles can have an ER shear strength as high as 29 kPa when the volume fraction of particles is 0.4 and the applied field is 5 kV . Results in the literature provide support for the concept and analysis. DA - 1998/11/21/ PY - 1998/11/21/ DO - 10.1088/0022-3727/31/22/021 VL - 31 IS - 22 SP - 3312-3315 SN - 0022-3727 ER - TY - JOUR TI - Microstructural factors influencing the properties of high surface area molybdenum nitride films converted from molybdenum trioxide films deposited via solution spray pyrolysis AU - Roberson, SL AU - Finello, D AU - Davis, RF T2 - JOURNAL OF MATERIALS RESEARCH DA - 1998/8// PY - 1998/8// DO - 10.1557/JMR.1998.0313 VL - 13 IS - 8 SP - 2237-2244 SN - 0884-2914 ER - TY - JOUR TI - Mechanical properties, ductility, and grain size of nanocrystalline iron produced by mechanical attrition AU - Malow, TR AU - Koch, CC T2 - METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE DA - 1998/9// PY - 1998/9// DO - 10.1007/s11661-998-0106-1 VL - 29 IS - 9 SP - 2285-2295 SN - 1073-5623 ER - TY - JOUR TI - Frequency-resolved microwave reflection photoconductance AU - Romanowski, A AU - Buczkowski, A AU - Karoui, A AU - Rozgonyi, GA T2 - JOURNAL OF APPLIED PHYSICS AB - The effect of the carrier recombination process in silicon on the microwave reflection coefficient is analyzed in the frequency domain. The process is described using a two level recombination/trapping model. Carrier recombination kinetics are characterized by four parameters, two of which are related to the recombination and the other to the trapping processes. These parameters are evaluated for Czochralski silicon wafers based on Nyquist plots. In the evaluation procedure, a nonlinear simplex method is used for fitting the experimental data to the model. DA - 1998/6/15/ PY - 1998/6/15/ DO - 10.1063/1.367946 VL - 83 IS - 12 SP - 7730-7735 SN - 0021-8979 ER - TY - JOUR TI - Finite element modeling of thermal residual stress in Tungsten/Tungsten-carbide composites AU - Wang, K. AU - Reeber, R. R. T2 - Ceramic Engineering and Science Proceedings DA - 1998/// PY - 1998/// VL - 19 IS - 4 SP - 177-184 ER - TY - JOUR TI - Endpoint uniformity sensing and analysis in silicon dioxide plasma etching using in situ mass spectrometry AU - Chambers, JJ AU - Min, K AU - Parsons, GN T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Mass spectroscopy is used to characterize the endpoint uniformity of silicon dioxide etching in an electron cyclotron resonance (ECR) plasma etch process. Etch products are observed using a two stage differentially pumped mass spectrometry system attached to the ECR process chamber. Specifically, using CF4 and D2 etch gases, the partial pressure of CO-containing etch products decays near the endpoint, and the rate of signal decay is directly correlated with the uniformity determined from optical interferometry thickness measurements. To correlate the mass spectrometer signal with the etch rate variation across the wafer, etch uniformity is altered by changing the ECR electromagnet geometry and by modifying the initial oxide uniformity. A COF2 etch product material balance is developed to model the observed concentration versus time data, resulting in a quantitative correlation between change in endpoint slope and uniformity. The ability to utilize a process-state sensor, such as a mass spectrometer, for wafer-state information will result in new approaches for sensing, optimizing, and controlling integrated circuit fabrication processes. DA - 1998/// PY - 1998/// DO - 10.1116/1.590332 VL - 16 IS - 6 SP - 2996-3002 SN - 1071-1023 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000077542300014&KeyUID=WOS:000077542300014 ER - TY - JOUR TI - Electron emission from diamond films AU - Zhirnov, , VV AU - Hren, JJ T2 - MRS BULLETIN DA - 1998/9// PY - 1998/9// DO - 10.1557/S0883769400029365 VL - 23 IS - 9 SP - 42-48 SN - 0883-7694 ER - TY - JOUR TI - Electron affinity and Schottky barrier height of metal-diamond (100), (111), and (110) interfaces AU - Baumann, PK AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - The electron emission properties of metal–diamond (100), (111), and (110) interfaces were characterized by means of UV photoemission spectroscopy (UPS) and field-emission measurements. Different surface cleaning procedures including annealing in ultrahigh vacuum (UHV) and rf plasma treatments were used before metal deposition. This resulted in diamond surfaces terminated by oxygen, hydrogen, or free of adsorbates. The electron affinity and Schottky barrier height of Zr or Co thin films were correlated by means of UPS. A negative electron affinity (NEA) was observed for Zr on any diamond surface. Co on diamond resulted in NEA characteristics except for oxygen-terminated surfaces. The lowest Schottky barrier heights were obtained for the clean diamond surfaces. Higher values were measured for H termination, and the highest values were obtained for O on diamond. For Zr, the Schottky barrier height ranged from 0.70 eV for the clean to 0.90 eV for the O-terminated diamond (100) surface. Values for Co ranged from 0.35 to 1.40 eV for clean- and O-covered (100) surfaces, respectively. The metal-induced NEA proved to be stable after exposure to air. For the oxygen-terminated diamond (100) surface a field-emission threshold of 79 V/μm was measured. Zr or Co deposition resulted in lower thresholds. Values as low as 20 V/μm were observed for Zr on the clean diamond (100) surface. Results for Zr or Co on H- or O-terminated surfaces were higher. H or O layers on diamond tend to cause an increase in the Schottky barrier height and the field-emission threshold field of Zr– and Co–diamond interfaces. The value of the electron affinity and Schottky barrier were correlated with work function and different initial surface preparation. The results were largely consistent with a model in which the vacuum level was related to the metal work function and the measured Schottky barrier. DA - 1998/2/15/ PY - 1998/2/15/ DO - 10.1063/1.366940 VL - 83 IS - 4 SP - 2072-2082 SN - 0021-8979 ER - TY - JOUR TI - Dependence of (0001) GaN/AlN valence band discontinuity on growth temperature and surface reconstruction AU - King, SW AU - Ronning, C AU - Davis, RF AU - Benjamin, MC AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - X ray and ultraviolet photoelectron spectroscopies have been used to determine the heterojunction valence band discontinuity at the (0001) GaN/AlN interface. Type I discontinuity values of 0.5±0.2 eV were determined for GaN grown on AlN at 650 °C and 0.8±0.2 eV for GaN grown on AlN at 800 °C. These values are critically evaluated with respect to film quality, the results of other experimental studies, and theory. DA - 1998/8/15/ PY - 1998/8/15/ DO - 10.1063/1.368355 VL - 84 IS - 4 SP - 2086-2090 SN - 0021-8979 ER - TY - JOUR TI - Cold photoconductivity in a system of interacting charge-transfer excitons at a donor-acceptor interface AU - Kiselev, SA AU - Hartung, E AU - Soos, ZG AU - Forrest, , SR AU - Agranovich, VM T2 - CHEMICAL PHYSICS AB - Computer simulations are used to investigate the phase transition to the conducting state in a system of interacting 2D charge-transfer excitons (CTEs) at a donor–acceptor interface. The phase transition arises due to strong dipole–dipole repulsion between CTEs which stimulates the population of free carriers in higher energy states even at low temperature. The random distribution of excitons and finite lifetime is explicitly taken into account. The critical concentration of CTEs and their energy distribution is calculated. Some features of spatial ordering of CTEs at the interface are considered. We also discuss the possibility of observing the predicted phenomena. DA - 1998/12/1/ PY - 1998/12/1/ DO - 10.1016/S0301-0104(98)00345-0 VL - 238 IS - 3 SP - 365-372 SN - 0301-0104 ER - TY - JOUR TI - Behavior of molybdenum nitrides as materials for electrochemical capacitors - Comparison with ruthenium oxide AU - Liu, TC AU - Pell, WG AU - Conway, BE AU - Roberson, SL T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - Ruthenium oxide , formed as a thin film on a Ru or Ti metal substrate, exhibits a large specific (cm−2) and almost constant, electrochemical capacitance over a 1.35 V range in aqueous . This behavior has led to its investigation and use as a material for fabrication of supercapacitor devices. However, its cost has encouraged search for other materials exhibiting similar behavior. Work reported in the present paper evaluates two nitrides of Mo, and MoN, as substitutes for . It is shown that very similar capacitance behavior to that of , films arises, e.g., in cyclic voltammetry and dc charging curves; in the former, almost mirror‐image anodic and cathodic current‐response profiles, characteristic of a capacitor, arise. However, the nitride materials have a substantially smaller voltage operating range of only some 0.7 V due to electrochemical decomposition above ca. 0.7 V vs. RHE. This limits their usefulness as a substitute for . Of interest is that the nitride films exhibit potential‐decay and potential‐recovery on open circuit after respective charge and forced discharge. The decay and recovery processes are logarithmic in time, indicating the role of internal faradaic charge redistribution processes. DA - 1998/6// PY - 1998/6// DO - 10.1149/1.1838571 VL - 145 IS - 6 SP - 1882-1888 SN - 0013-4651 ER - TY - JOUR TI - A numerical study of shock-induced particle velocity dispersion in solid mixtures AU - Yano, K AU - Horie, Y T2 - JOURNAL OF APPLIED PHYSICS AB - Shock-induced particle velocity dispersion in solid mixtures was numerically investigated using two approaches: discrete element simulation and continuum mixture calculation. Results show (i) a trend-wise agreement between the two models, (ii) nonequilibrium distributions of particle velocity dispersion, and (iii) particle velocity dispersions of 20–100 m/s for a 10 GPa shock wave in Ni/Al mixtures and 5–70 m/s for a 5 GPa shock wave in Ti/Teflon mixtures. Particle velocity dispersions of this magnitude are thought to be the driving mechanism for initiation of chemical reactions in reactive solid mixtures. DA - 1998/8/1/ PY - 1998/8/1/ DO - 10.1063/1.368197 VL - 84 IS - 3 SP - 1292-1298 SN - 0021-8979 ER - TY - JOUR TI - A free electron laser-photoemission electron microscope system (FEL-PEEM) AU - Ade, H AU - Yang, W AU - English, SL AU - Hartman, J AU - Davis, RF AU - Nemanich, RJ AU - Litvinenko, VN AU - Pinayev, , IV AU - Wu, Y AU - Madey, JMJ T2 - SURFACE REVIEW AND LETTERS AB - We report first results from our effort to couple a high resolution photoemission electron microscope (PEEM) to the OK-4 ultraviolet free electron laser at Duke University (OK-4/Duke UV FEL). The OK-4/Duke UV FEL is a high intensity source of tunable monochromatic photons in the 3–10 eV energy range. This tunability is unique and allows us to operate near the photoemission threshold of any samples and thus maximize sample contrast while keeping chromatic berrations in the PEEM minimal. We have recorded first images from a variety of samples using spontaneous radiation from the OK-4/ Duke UV FEL in the photon energy range of 4.0–6.5 eV. Due to different photothreshold emission from different sample areas, emission from these areas could be turned on (or off) selectively. We have also observed relative intensity reversal with changes in photon energy which are interpreted as density-of-state contrast. Usable image quality has been achieved, even though the output power of the FEL in spontaneous emission mode was several orders of magnitude lower than the anticipated full laser power. The PEEM has achieved a spatial resolution of 12 nm. DA - 1998/12// PY - 1998/12// DO - 10.1142/S0218625X98001596 VL - 5 IS - 6 SP - 1257-1268 SN - 0218-625X ER - TY - JOUR TI - The effects of PbTiO3 thin template layer and Pt/RuO2 hybrid electrode on the ferroelectric properties of sol-gel derived PZT thin film AU - Kim, SH AU - Choi, YS AU - Kim, CE AU - Yang, DY T2 - THIN SOLID FILMS AB - Lead zirconate titanate, Pb(Zr0.52Ti0.48)O3 (PZT) thin film with a thin PbTiO3 template layer was successfully fabricated onto Pt/RuO2 hybrid electrode by using a new alkoxide-alkanolamine sol-gel method. The resulting film showed a well-developed dense grain structure with uniform distribution. It was observed that the use of Pt/RuO2 hybrid electrode helped reduce the amount of the Pb2Ru2O7−x second phase as well as the leakage current by about three orders of magnitude. Typical P-E hysteresis loops were observed even at the low applied voltage of 5 V and the measured values of 2Ps, 2Pr and 2Ec were 93 μC/cm2, 48 μC/cm2 and 78 kV/cm, respectively. Polarization versus fatigue characteristics showed little degradation up to 1011 cycles. DA - 1998/7/18/ PY - 1998/7/18/ DO - 10.1016/S0040-6090(98)00486-6 VL - 325 IS - 1-2 SP - 72-78 SN - 0040-6090 KW - ferroelectric thin film KW - hybrid electrode KW - template layer KW - sol-gel method KW - PZT KW - fatigue degradation ER - TY - JOUR TI - Systematic differences among nominal reference dielectric function spectra for crystalline Si as determined by spectroscopic ellipsometry AU - Bell, KA AU - Mantese, L AU - Rossow, U AU - Aspnes, DE T2 - THIN SOLID FILMS AB - Results of the first systematic investigation of differences among reference-quality ellipsometrically measured pseudodielectric function 〈ε〉 spectra of crystalline Si are discussed. These data are nominally used to approximate the bulk dielectric function of this material for optical modeling. In addition to the expected influence of residual overlayers, we identify surface-local-field and energy-derivative effects even between spectra obtained for seemingly identical H-terminated surfaces. Model calculations indicate that these effects account for nearly all differences among spectra studied. The isotropic contribution to the surface-local-field effect is also reported. DA - 1998/2// PY - 1998/2// DO - 10.1016/S0040-6090(97)00804-3 VL - 313 IS - 1998 Feb. SP - 161-166 SN - 0040-6090 KW - ellipsometry KW - optical modeling KW - dielectric function KW - silicon ER - TY - JOUR TI - Stability of Si-O-F low-K dielectrics: Attack by water molecules as function of near-neighbor Si-F bonding arrangements AU - Yang, H AU - Lucovsky, G T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS AB - Ab initio configuration interaction calculations have been previously used to account for the relatively large decreases in the static dielectric constant of Si-O-F alloys with low alloy concentrations of F atoms, ∼22% for F concentrations of ∼10 at. %. The present study addresses the stability of these alloy films with respect to attack of Si-F bonds by water molecules. The present calculations show that the reaction: H2O+2Si-F→2HF+Si-O-Si is exothermic by about 0.7 eV. Our calculations focus on the reaction energetics and geometries as a function of the distance between the F atoms of the Si-F groups and water molecules. Combining these calculations for interactions with H2O with a statistical model of bonding in the alloy films as presented in our previous article, an upper limit for chemically stable F corporation has been determined to be ∼10–12 at. % F, which corresponds to static dielectric constant of 3.2–3.4. DA - 1998/// PY - 1998/// DO - 10.1116/1.581181 VL - 16 IS - 3 SP - 1525-1528 SN - 0734-2101 ER - TY - JOUR TI - Spectroscopic ellipsometry and low-temperature reflectance: complementary analysis of GaN thin films AU - Edwards, NV AU - Yoo, SD AU - Bremser, MD AU - Horton, MN AU - Perkins, NR AU - Weeks, TW AU - Liu, H AU - Stall, RA AU - Kuech, TF AU - Davis, RF AU - Aspnes, DE T2 - THIN SOLID FILMS AB - Abstract We report spectroscopic ellipsometry (SE) and low-temperature reflectance data on epitaxial GaN thin-film samples covering the widest range of tensile and compressive stress (−3.8 to 3.5 kbar) thus far. SE allows us to assess the preparation of smooth and abrupt GaN surfaces by chemical treatments in real time, and, coupled with the reflectance data, the E d n /d E contribution to dispersion, which is important for laser action. The reflectance data explicitly show the non-linear behavior of the B-A and C-A splittings vs. the energy of the A exciton. Lineshape ambiguities that hindered previous interpretations have been resolved with reciprocal space analysis, allowing us to obtain band parameters such as Δ SO =17.0±1 meV and Δ CF =9.8±1 meV with increased confidence. DA - 1998/2// PY - 1998/2// DO - 10.1016/S0040-6090(97)00815-8 VL - 313 IS - 1998 Feb. SP - 187-192 SN - 0040-6090 KW - GaN KW - spectroscopic ellipsometry KW - reflectance KW - valence bands KW - excitons KW - reciprocal space analysis ER - TY - JOUR TI - Silane consumption and conversion analysis in amorphous silicon and silicon nitride plasma deposition using in situ mass spectroscopy AU - Chowdhury, AI AU - Klein, TM AU - Anderson, TM AU - Parsons, GN T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS AB - In situ mass spectroscopy is used to sense plasma deposition of silicon and silicon nitride, to analyze gas phase reactant depletion, and the efficiency of silane conversion into the thin film. A double-differentially pumped quadrupole mass spectrometer was used to monitor the SiH4, Si2H6, and H2 effluent from 100% SiH4 and 2% SiH4/He silicon deposition, and SiH4/He/N2 silicon nitride deposition processes. No significant changes in gas phase nitrogen related species were observed during nitride deposition. However, the Si species show significant process dependence allowing reaction analysis. Disilane species were produced at low powers in the SiH4/He/N2 process, but no amino–silane species were observed. The silane consumption and silicon incorporation efficiency are shown to depend on gas dilution, residence time, and reactor geometry. DA - 1998/// PY - 1998/// DO - 10.1116/1.581117 VL - 16 IS - 3 SP - 1852-1856 SN - 0734-2101 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000074150500084&KeyUID=WOS:000074150500084 ER - TY - JOUR TI - Plasma enhanced selective area microcrystalline silicon deposition on hydrogenated amorphous silicon: Surface modification for controlled nucleation AU - Smith, LL AU - Read, WW AU - Yang, CS AU - Srinivasan, E AU - Courtney, CH AU - Lamb, HH AU - Parsons, Gregory T2 - Journal of Vacuum Science & Technology a-Vacuum Surfaces and Films AB - Selective deposition of μc-Si on hydrogenated amorphous silicon is demonstrated using time-modulated silane reactant flow in a low temperature plasma enhanced process. Alternating cycles of thin silicon layer deposition and atomic hydrogen exposure result in silicon layers on receptive surfaces, with no net deposition on nonreceptive areas of the substrate. Selective deposition could be useful to form self-aligned contacts in hydrogenated amorphous silicon (a-Si:H transistor applications. However, a problem commonly observed in low temperature selective deposition is that the selective process tends to etch amorphous silicon, harming the devices. We describe a technique involving Mo metallization that stabilizes the a-Si:H surface with respect to hydrogen plasma exposure and allows selective μc-Si deposition on a-Si:H in device structures, while avoiding deposition on the top SiNx insulator material. Surfaces and subsequent selective nucleation and growth were characterized using atomic force microscopy, x-ray photoelectron spectroscopy, and Auger electron spectroscopy, which revealed the presence of Mo incorporation in the a-Si:H surface remaining after complete removal of the metal layer. A direct comparison of selective deposition experiments on films prepared with and without Mo treatment demonstrate that the metallization stabilizes nucleation of microcrystalline silicon on amorphous silicon surfaces. DA - 1998/// PY - 1998/// DO - 10.1116/1.581144 VL - 16 IS - 3 SP - 1316-1320 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000074150400079&KeyUID=WOS:000074150400079 ER - TY - PCOMM TI - Photoelectrochemical capacitance-voltage measurements in GaN AU - Stutz, CE AU - Mack, M AU - Bremser, MD AU - Nam, OH AU - Davis, RF AU - Look, DC DA - 1998/5// PY - 1998/5// DO - 10.1007/s11664-998-0182-4 SP - L26-L28 KW - carrier concentration depth profile KW - GaN KW - photoelectrochemical etching ER - TY - JOUR TI - Phonon density of states of bulk gallium nitride AU - Nipko, JC AU - Loong, CK AU - Balkas, CM AU - Davis, RF T2 - APPLIED PHYSICS LETTERS AB - We report the measured phonon density of states of a bulk GaN powder by time-of-flight neutron spectroscopy. The observed one-phonon excitation spectrum consists of two broad bands centered at about 23 and 39 meV corresponding to the acoustic and the first group of optical phonons; two sharp bands of upper optic modes at about 75 and 86 meV; and a gap of 45–65 meV. The phonon dispersion curves, lattice specific heat, and Debye temperature are calculated from fitting the data with a rigid-ion model. DA - 1998/7/6/ PY - 1998/7/6/ DO - 10.1063/1.121714 VL - 73 IS - 1 SP - 34-36 SN - 0003-6951 ER - TY - PAT TI - Oriented diamond film structures on nondiamond substrates AU - Zhu, W. AU - Yang, P.-C. AU - Glass, J. T. C2 - 1998/// DA - 1998/// PY - 1998/// ER - TY - JOUR TI - Optimization of nitrided gate dielectrics by plasma-assisted and rapid thermal processing AU - Lucovsky, G AU - Niimi, H AU - Wu, Y AU - Parker, CR AU - Hauser, , JR T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - This article addresses several aspects of nitrogen atom (N atom) incorporation into ultrathin gate oxides including: (i) monolayer incorporation of N atoms at the Si–SiO2 interfaces to reduce tunneling currents and improve device reliability; and (ii) the incorporation of silicon nitride films into stacked oxide–nitride (ON) gate dielectrics to (a) increase the capacitance in ultrathin dielectrics without decreasing film thickness, and (b) suppress boron atom (B atom) diffusion from p+ polycrystalline Si gate electrodes through the dielectric layer to the Si substrate channel region. The results of this article demonstrate that these N-atom spatial distributions can be accomplished by low thermal budget, single wafer processing which includes (i) low-temperature (300 °C) plasma assisted oxidation, nitridation, and/or deposition to achieve the desired N-atom incorporation, followed by (ii) low thermal budget (30 s at 900 °C) rapid thermal annealing to promote chemical and structural bulk and interface relaxation. DA - 1998/// PY - 1998/// DO - 10.1116/1.581291 VL - 16 IS - 3 SP - 1721-1729 SN - 0734-2101 ER - TY - JOUR TI - Optical characterization of lateral epitaxial overgrown GaN layers AU - Freitas, JA AU - Nam, OH AU - Davis, RF AU - Saparin, GV AU - Obyden, SK T2 - APPLIED PHYSICS LETTERS AB - The optical properties of homoepitaxial GaN layers deposited by organometallic vapor phase epitaxy on stripe-patterned GaN films on 6H-SiC substrates have been investigated. Analysis of the spatially-resolved Raman scattering spectra indicate an improvement in material quality of the overgrown region. Room-temperature color cathodoluminescence imaging and low-temperature photoluminescence measurements indicate that a donor and an acceptor, different from those detected in the underlying GaN/AlN/SiC substrate, have been incorporated in the epitaxial layer. Detailed photoluminescence studies of the near-band-edge emission strongly suggest that Si is the additional donor detected in the homoepitaxial GaN layer. Its occurrence, along with that of an acceptor-related defect which is primarily found in the laterally overgrown region, is discussed. DA - 1998/6/8/ PY - 1998/6/8/ DO - 10.1063/1.121517 VL - 72 IS - 23 SP - 2990-2992 SN - 0003-6951 ER - TY - JOUR TI - Nuclear electric quadrupole moment of Li-6 AU - Cederberg, J AU - Olson, D AU - Larson, J AU - Rakness, G AU - Jarausch, K AU - Schmidt, J AU - Borovsky, B AU - Larson, P AU - Nelson, B T2 - PHYSICAL REVIEW A AB - The molecular beam electric resonance technique has been used to examine the hyperfine spectrum of ${}^{6}{\mathrm{Li}}^{19}\mathrm{F}$ for the purpose of obtaining an improved value of the ratio of the electric quadrupole moments of the two lithium nuclei. A total of 29 transitions in vibrational states 0-2 and rotational states 1-4 have been included in a fit to determine the Li nuclear quadrupole interaction along with the magnetic spin-rotation and spin-spin interactions. The magnetic interactions are consistent with values calculated from the previously reported ${}^{7}{\mathrm{Li}}^{19}\mathrm{F}$ values, but those have been refitted to take advantage of the new information from ${}^{6}{\mathrm{Li}}^{19}\mathrm{F}$. The electric quadrupole moment ratio of the two lithium isotopes determined from measurements on the two forms of LiF is ${Q(}^{6}\mathrm{Li}{)/Q(}^{7}\mathrm{Li})=0.020161\ifmmode\pm\else\textpm\fi{}0.000013$ (one standard deviation estimate). DA - 1998/4// PY - 1998/4// DO - 10.1103/PhysRevA.57.2539 VL - 57 IS - 4 SP - 2539-2543 SN - 1094-1622 ER - TY - JOUR TI - Multiple sample analysis of spectroscopic ellipsometry data of semi-transparent films AU - Jarrendahl, K AU - Arwin, H T2 - THIN SOLID FILMS AB - When analyzing spectroscopic ellipsometry data it can be difficult to find unique solutions if, for instance, the dielectric function of a film must be found together with the film thickness. One method to find the solutions is `multiple sample analysis'. The basic assumption for this method is that the optical properties of the unknown layers are identical in all samples. In the analysis procedure a set of samples with different film thicknesses are prepared and measured, preferably at multiple angles of incidence. Several (one for each sample) identical optical models are then defined with coupled optical properties of the unknown layers and all data are fitted simultaneously. This will give solutions for the dielectric function of the films and the film thicknesses due to parameter decoupling. The analysis can also be extended to more complex samples including more than one film thickness, surface and interface roughness, and porosity. In this study we have applied the multiple sample analysis method to find dielectric functions, film thicknesses and surface roughnesses of thin films of Ta2O5, ScN and CeO2. DA - 1998/2// PY - 1998/2// DO - 10.1016/S0040-6090(97)00781-5 VL - 313 SP - 114-118 SN - 0040-6090 KW - spectroscopic ellipsometry KW - multiple sample analysis KW - Ta2O5 KW - ScN KW - CeO2 ER - TY - JOUR TI - Morphological and isothermal diffusive probe analyses of low-molecular-weight diblock copolymers AU - Hong, SU AU - Laurer, JH AU - Zielinski, JM AU - Samseth, J AU - Smith, SD AU - Duda, JL AU - Spontak, RJ T2 - MACROMOLECULES AB - While numerous scattering and rheological studies have investigated the disordering mechanism of low-molecular-weight poly(styrene-b-isoprene) (SI) diblock copolymers, relatively few efforts have addressed the real-space morphologies and transport properties of such copolymers at conditions near the order−disorder transition (ODT). In this work, the morphological features of seven compositionally symmetric (50/50 w/w S/I) copolymers ranging in molecular weight from 5000 to 20000, as well as several of their blends, are examined by transmission electron microscopy and small-angle neutron scattering. These results are used to interpret toluene gravimetric sorption data collected at various temperatures. At temperatures above the styrenic glass transition temperature, microphase-ordered copolymer melts are found to exhibit Fickian diffusion. In the case of a copolymer with an experimentally accessible ODT, anomalous sorption (as evidenced by equilibrium overshoot in gravimetric mass-uptake curves) is observed at temperatures near, but below, the ODT. Within the disordered state, Fickian diffusion is regained, indicating that the onset of anomalous diffusion is related to a solvent-induced ODT under isothermal conditions. DA - 1998/4/7/ PY - 1998/4/7/ DO - 10.1021/ma971516e VL - 31 IS - 7 SP - 2174-2184 SN - 0024-9297 ER - TY - JOUR TI - Microporous, responsive hydroxypropyl cellulose gels. 1. Synthesis and microstructure AU - Kabra, BG AU - Gehrke, SH AU - Spontak, RJ T2 - MACROMOLECULES AB - An effective technique for the synthesis of microporous gels is developed along with correlations between synthesis conditions and microstructure. Such gels have substantially different properties than their nonporous analogues. Microporous hydroxypropyl cellulose (HPC) gels were prepared by heating aqueous HPC solutions above their lower critical solution temperatures (LCST's) while cross-linking the polymer with divinyl sulfone. The effective porosity of the gel increased from 23 to 76% by decreasing HPC concentration from 22.6 to 9 wt %, as anticipated from the system phase diagram. The pore size range decreased from 0.5−9.0 to 0.05−0.2 μm by increasing reaction time before phase separation from 1.5 to 25 min, demonstrating that cross-linking in the homogeneous state limits the extent of phase separation possible. Gel morphology changed from open-celled to closed-celled by decreasing reaction time in the phase-separated state, which limits cross-linking in the polymer-rich phase. DA - 1998/4/7/ PY - 1998/4/7/ DO - 10.1021/ma970418q VL - 31 IS - 7 SP - 2166-2173 SN - 1520-5835 ER - TY - JOUR TI - Low-field bulk defect generation during uniform carrier injection into the gate insulator of insulated gate field effect transistors at various temperatures AU - Kim, HS AU - Williams, CK AU - Reisman, A T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 1998/7// PY - 1998/7// DO - 10.1007/s11664-998-0117-0 VL - 27 IS - 7 SP - 908-914 SN - 0361-5235 KW - electron trapping KW - oxide defects KW - trap generation ER - TY - JOUR TI - Interface studies of tungsten nitride and titanium nitride composite metal gate electrodes with thin dielectric layers AU - Claflin, B AU - Binger, M AU - Lucovsky, G T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Interface formation between reactively sputtered tungsten nitride (WNx) or titanium nitride (TiNx) metallic films and thermally grown silicon dioxide (SiO2) layers is studied by interrupted growth with on-line Auger electron spectroscopy. For both composite metals, growth proceeds directly without a metal precursor layer. The chemical stability of these WNx/SiO2 and TiNx/SiO2 interfaces is investigated by rapid thermal annealing up to 850 °C. The WNx/SiO2 interface is stable up to 650 °C while TiNx/SiO2 is stable below 850 °C. Metal–oxide–semiconductor capacitors have been fabricated with WNx and TiNx gates and 7.5 nm thick thermal oxide gate dielectrics with interface trap densities, Dit&lt;2×1011 cm−2 eV−1. Capacitance–voltage and current–voltage measurements indicate the Fermi level for TiNx lies near midgap in Si, while for WNx it lies closer to the valence band. DA - 1998/// PY - 1998/// DO - 10.1116/1.581297 VL - 16 IS - 3 SP - 1757-1761 SN - 1520-8559 ER - TY - JOUR TI - Influence of an electric field on grain growth in extruded NaCl AU - Yang, D AU - Conrad, H T2 - SCRIPTA MATERIALIA AB - Spark plasma sintering (SPS), also known as pulsed electric current sintering (PECS) or field-assisted sintering technique (FAST), belongs to a class of powder metallurgy techniques. In SPS, the sample is simultaneously subjected to a uniaxial pressure and electrical current in a vacuum or protective atmosphere. Although the fundamental principles of this procedure were first proposed over 50 years ago, SPS acquired major importance only within the last 20 years. Scholars come to realize that SPS technique enables control of the powder surface condition, atomic diffusion behavior, and phase stability and crystal growth behavior, as well as accelerating densification of hard-to-sinter materials. This review summarizes the latest research findings with respect to experimental procedures, densification behaviors, microstructural characteristics, and mechanical properties of various traditional and novel materials synthesized using SPS, mainly highlighting the heating mechanisms in SPS and the effects induced by multi-physical fields on materials. In addition, influences of operating parameters containing current, voltage, and uniaxial pressure on product characteristics are reviewed for a wide range of materialsincluding hard-to-sinter materials, carbon-containing materials, nanocrystalline materials, non-equilibrium materials, gradient materials, interconnect materials, complex shape materials, and advanced functional materials. DA - 1998/4/3/ PY - 1998/4/3/ DO - 10.1016/S1359-6462(98)00042-6 VL - 38 IS - 9 SP - 1443-1448 SN - 1359-6462 ER - TY - PCOMM TI - Growth of Fe3N films via chemical vapor deposition of iron acetylacetonate and anhydrous ammonia AU - Roberson, S. L. AU - Finello, D. AU - Banks, A. D. AU - Davis, R. F. DA - 1998/// PY - 1998/// SP - 47-50 ER - TY - JOUR TI - Fine structure of near-band-edge photoluminescence in He+-irradiated GaN grown on SiC AU - Joshkin, VA AU - Parker, CA AU - Bedair, SM AU - Krasnobaev, LY AU - Cuomo, JJ AU - Davis, RF AU - Suvkhanov, A T2 - APPLIED PHYSICS LETTERS AB - The effect of He ion implantation on the optical properties of epitaxial GaN-on-SiC was studied. We observed that He+ irradiation increases the relative intensity of the “blue emission” and resistivity of GaN films and decreases the intensity of the near-band-edge photoluminescence. Because the intensity of the main peak is drastically decreased, the fine structure of the near-band-edge photoluminescence in GaN after He+ irradiation was observed. From a comparison of observed sharp lines with photoluminescence peaks of GaN doped with oxygen, we conclude that oxygen can produce a complex, which is characterized by a strong localization of free carriers and a large lattice distortion. The zero-phonon line of this defect has energy close to the band-gap energy of GaN. DA - 1998/6/1/ PY - 1998/6/1/ DO - 10.1063/1.121474 VL - 72 IS - 22 SP - 2838-2840 SN - 0003-6951 ER - TY - JOUR TI - Electron emission mechanism from cubic boron nitride-coated molybdenum emitters AU - McCarson, BL AU - Schlesser, R AU - McClure, MT AU - Sitar, Z T2 - APPLIED PHYSICS LETTERS AB - The energy distribution of field-emitted electrons from Mo tips coated with intrinsic cubic boron nitride (c-BN) was studied in an effort to determine the origin of the emitted electrons. Voltage-dependent field-emission energy distribution (V-FEED) spectra were collected from the Mo emitters under ultra-high-vacuum conditions both before and after being coated. Emission current at a given voltage increased by as much as two orders of magnitude for the c-BN-coated emitters relative to bare emitters. The energy of field-emitted electrons from the c-BN-coated emitters was linearly dependent upon the applied voltage. Extrapolation of V-FEED data from c-BN-coated emitters to the flatband condition evidenced that the electrons were emitted from the conduction-band minimum of the c-BN coating at the c-BN/vacuum interface. DA - 1998/6/1/ PY - 1998/6/1/ DO - 10.1063/1.121492 VL - 72 IS - 22 SP - 2909-2911 SN - 0003-6951 ER - TY - JOUR TI - Electron emission characteristics of GaN pyramid arrays grown via organometallic vapor phase epitaxy AU - Ward, BL AU - Nam, OH AU - Hartman, JD AU - English, SL AU - McCarson, BL AU - Schlesser, R AU - Sitar, Z AU - Davis, RF AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - Selective growth of arrays of silicon-doped GaN (Si:GaN) pyramids for field emitter applications has been achieved. The electron emission characteristics of these arrays has been measured using techniques such as field emission, field emission energy distribution analysis (FEED), photoemission electron microscopy (PEEM), and field emission electron microscopy (FEEM). The field emission current–voltage (I–V) results indicate an average threshold field as low as 7 V/μm for an emission current of 10 nA. It is suggested that the low threshold field value is a consequence of both the low work function of Si:GaN and the field enhancement of the pyramids. The results of the FEEM and FEED measurements indicate agreement with the field emission I–V characteristics. The FEED results indicate that the Si:GaN pyramids are conducting, and that no significant ohmic losses are present between the top contact to the array and the field emitting pyramids. The PEEM and FEEM images show that the emission from the arrays is uniform over a 150 μm field of view. DA - 1998/11/1/ PY - 1998/11/1/ DO - 10.1063/1.368775 VL - 84 IS - 9 SP - 5238-5242 SN - 0021-8979 ER - TY - JOUR TI - Effects of a pulsed magnetic treatment on the fatigue of low carbon steel AU - Fahmy, Y AU - Hare, T AU - Tooke, R AU - Conrad, H T2 - SCRIPTA MATERIALIA AB - Results of cavitation erosion tests for EN8 steel, nickel-aluminium bronze (NAB), 70/30 brass and aluminium alloy AA2014-T6 following alternating magnetic field (AMF) treatment are presented. These alloys were selected because of their magnetic nature; EN8 steel is ferromagnetic, NAB and 70/30 brass are diamagnetic and AA2014 alloy is paramagnetic. The indirect cavitation erosion tests (ASTM G32–10 standard) were fulfilled at a frequency of 20 kHz in deionized water which was maintained at room temperature and ambient pressure for a predetermined time. The results show significant decrease in the mass loss for all samples that had underg1 AMF treatment. The eroded samples were characterised by means of scanning electron microscopy, while microhardness measurements showed an increase in the surface hardness as a result of the AFM treatment. The results of X-ray diffraction indicated formation of more compressive residual stresses following treatment, while examination by transmission electron microscopy showed evidence of dislocation movement away from grain boundaries. In the case of the NAB and 20014-T6 alloys, there was evidence of new precipitation. By considering the deformed state and the magnetic nature of each alloy, mechanisms explaining the increase in the cavitation erosion resistance due to the treatment are proposed and discussed. DA - 1998/4/3/ PY - 1998/4/3/ DO - 10.1016/S1359-6462(98)00046-3 VL - 38 IS - 9 SP - 1355-1358 SN - 1359-6462 ER - TY - JOUR TI - Depth-dependent spectroscopic defect characterization of the interface between plasma-deposited SiO(2) and silicon AU - Schafer, J AU - Young, AP AU - Brillson, LJ AU - Niimi, H AU - Lucovsky, G T2 - APPLIED PHYSICS LETTERS AB - We demonstrate the use of low-energy cathodoluminescence spectroscopy (CLS) to study optical transitions at defect bonding arrangements at Si–SiO2 interfaces prepared by low-temperature plasma deposition. Variable-depth excitation achieved by different electron injection energies provides a clear distinction between luminescence derived from (i) the near-interface region of the oxide film, (ii) the Si–SiO2 interface, and (iii) the underlying crystalline Si substrate. Cathodoluminescence bands at ∼0.8 and 1 eV are assigned to interfacial Si atom dangling bonds with different numbers of back-bonded Si and O atoms. CLS also reveals higher photon energy features: two bands at ∼1.9 and 2.7 eV assigned to suboxide bonding defects in the as-grown oxide films, as well as a substrate-related feature at ∼3.4 eV. The effects of hydrogenation at 400 °C and rapid thermal annealing at 900 °C, and especially the combination of both process steps is shown to dramatically reduce the intensities of the CLS features assigned to interfacial and suboxide bonding defects. DA - 1998/8/10/ PY - 1998/8/10/ DO - 10.1063/1.122003 VL - 73 IS - 6 SP - 791-793 SN - 0003-6951 ER - TY - JOUR TI - Compressive mechanical behavior of nanocrystalline Fe investigated with an automated ball indentation technique AU - Malow, TR AU - Koch, CC AU - Miraglia, PQ AU - Murty, KL T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Nanocrystalline (nc) iron was produced by mechanical attrition and compacted into near fully dense samples. Isothermal annealing at 800 K resulted in grain sizes between 15 and 24 nm. A newly available Automated Ball Indentation system was used to study the compressive mechanical properties of the samples. The ABI method proved useful in examining the mechanical properties of nc iron on a more quantitative level than previously possible by conventional hardness testing methods. Stress–strain curves were obtained which indicated a compressive behavior similar to that of perfectly plastic materials: low strain hardening at high flow stresses around 3 GPa and a low room-temperature strain-rate sensitivity. The flow stresses were independent of the grain size in the range of the present study. The deformation pile-up around the indentations seems to have formed inhomogeneously, exhibiting intense plastic deformation in localized shear bands. DA - 1998/8/31/ PY - 1998/8/31/ DO - 10.1016/s0921-5093(98)00661-3 VL - 252 IS - 1 SP - 36-43 SN - 0921-5093 KW - mechanical attrition KW - mechanical behavior in compression KW - nanocrystalline Fe ER - TY - JOUR TI - Combined MOS/EBIC and TEM study of electrically active defects in SOI wafers AU - Kononchuk, O. AU - Bondarenko, I. AU - Rozgonyi, G. T2 - Diffusion and Defect Data. [Pt. B], Solid State Phenomena DA - 1998/// PY - 1998/// VL - 63-4 IS - 1998 SP - 61-67 ER - TY - JOUR TI - Coalesced oriented diamond films on nickel AU - Yang, PC AU - Wolden, CA AU - Liu, W AU - Schlesser, R AU - Davis, RF AU - Prater, JT AU - Sitar, Z T2 - JOURNAL OF MATERIALS RESEARCH DA - 1998/5// PY - 1998/5// DO - 10.1557/JMR.1998.0157 VL - 13 IS - 5 SP - 1120-1123 SN - 0884-2914 ER - TY - JOUR TI - Characterization of copper-diamond (100), (111), and (110) interfaces: Electron affinity and Schottky barrier AU - Baumann, PK AU - Nemanich, RJ T2 - PHYSICAL REVIEW B AB - In this study ultraviolet photoemission spectroscopy was employed to correlate the electron affinity and Schottky barrier height of Cu films on type-IIb ($p$-type) diamond (100), (111), and (110) surfaces. Furthermore, field emission measurements were correlated with the effective electron affinity of the samples. Prior to deposition the diamond samples were cleaned by various annealings and plasma treatments in ultrahigh vacuum. Annealing the diamond substrates to 1150 \ifmmode^\circ\else\textdegree\fi{}C resulted in adsorbate-free surfaces with a positive electron affinity. A negative electron affinity (NEA) was induced after depositing 1 \AA{} of Cu on the clean surface. The Schottky barrier heights for the clean surfaces ranged from 0.30 eV for the (111) surface to 0.70 eV for the (100) surface. Depositing Cu onto H-terminated surfaces exhibiting a NEA still resulted in a NEA on all surfaces. However, the Schottky barrier heights were larger, ranging from 0.50 eV for the (111) surface to 0.90 eV for the (100) and (110) surfaces. The metal-induced NEA has been found to be stable to exposure to air. Following a 500 \ifmmode^\circ\else\textdegree\fi{}C annealing an oxygen-terminated (100) surface with a positive electron affinity was obtained. Cu deposition resulted in a positive electron affinity and the largest Schottky barrier height with 1.60 eV. A field emission threshold field of 79 V/\ensuremath{\mu}m was obtained for an oxygen-terminated diamond (100) surface. Values of 20, 25, and 53 V/\ensuremath{\mu}m were measured for Cu on clean, H- and O-terminated surfaces, respectively. Based on these experiments, it is suggested that chemisorbed species such as H or O on diamond surfaces cause an increase in the Schottky barrier as well as in the field emission threshold field after Cu deposition. DA - 1998/7/15/ PY - 1998/7/15/ DO - 10.1103/physrevb.58.1643 VL - 58 IS - 3 SP - 1643-1654 SN - 1550-235X ER - TY - JOUR TI - Carbon nitride deposited using energetic species: A review on XPS studies AU - Ronning, C. AU - Feldermann, H. AU - Merk, R. AU - Hofsass, H. AU - Reinke, P. AU - Thiele, J. U. T2 - Physical Review. B, Condensed Matter and Materials Physics DA - 1998/// PY - 1998/// VL - 58 IS - 4 SP - 2207-2215 ER - TY - JOUR TI - Analysis of reactor geometry and diluent gas flow effects on the metalorganic vapor phase epitaxy of AlN and GaN thin films on alpha(6H)-SiC substrates AU - Hanser, AD AU - Wolden, CA AU - Perry, WG AU - Zheleva, T AU - Carlson, EP AU - Banks, AD AU - Therrien, RJ AU - Davis, RF T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 1998/4// PY - 1998/4// DO - 10.1007/s11664-998-0394-7 VL - 27 IS - 4 SP - 238-245 SN - 0361-5235 KW - AlN KW - diluent KW - doping KW - GaN KW - metalorganic vapor phase epitaxy (MOVPE) KW - photoluminescence (PL) KW - reactor modeling ER - TY - JOUR TI - Analysis of optical spectra by Fourier methods AU - Yoo, SD AU - Edwards, NV AU - Aspnes, DE T2 - THIN SOLID FILMS AB - Results of a systematic investigation of reciprocal-space analysis, applied to optical spectroscopy, are reported. Filtering procedures for removing baseline and noise artifacts are more effective in reciprocal- than in real-space. Also, correlations among parameters are reduced and the functional dependence of real-space lineshapes need be known a priori only in very general terms. We apply reciprocal-space analysis to achieve accurate values of critical point energies for the E1 and E1+Δ1 transitions of GaAs from ellipsometric spectra and to locate critical point energies in low-temperature reflectance data of GaN. We show that data may easily be corrected for systematic artifacts such as the monochromator slit width, an optimum slit width can be defined, and the degree of improvement needed to achieve a particular level of performance can be predicted. DA - 1998/2// PY - 1998/2// DO - 10.1016/S0040-6090(97)00801-8 VL - 313 IS - 1998 Feb. SP - 143-148 SN - 0040-6090 KW - Fourier analysis KW - critical points KW - spectroscopic ellipsometry KW - reflectance KW - filtering ER - TY - JOUR TI - An attenuated total reflectance cell for analysis of small molecule diffusion in polymer thin films with Fourier-transform infrared spectroscopy AU - Balik, CM AU - Simendinger, WH T2 - POLYMER AB - A cell is described for characterizing the diffusion of small molecules through thin polymer films using attenuated total reflectance (ATR) Fourier-transform infrared spectroscopy. The cell is designed to be used with precast (commercially extruded) polymer films, removing the need to cast the film directly onto the ATR crystal and allowing the as-processed transport properties of the film to be assessed. Pressurized gas is used to maintain contact between the polymer film and the ATR crystal during the diffusion experiment. Data are presented to demonstrate the use of this cell for measuring the diffusion of a gas (CO2), two liquids (amyl acetate and limonene), and simultaneous diffusion of individual components from a liquid mixture (5050 amyl acetate/limonene) through thin polymer films. In the last case, it was found that pure penetrant transport rates do not necessarily apply to diffusion of the same penetrants from a mixture. Diffusion coefficients obtained from the ATR cell compare favourably with values obtained gravimetrically for the same polymers and penetrants. DA - 1998/9// PY - 1998/9// DO - 10.1016/S0032-3861(97)10309-3 VL - 39 IS - 20 SP - 4723-4728 SN - 0032-3861 KW - diffusion KW - polymers KW - small molecules ER - TY - JOUR TI - Ultrathin oxide gate dielectrics prepared by low temperature remote plasma-assisted oxidation AU - Niimi, H AU - Lucovsky, G T2 - SURFACE & COATINGS TECHNOLOGY AB - Monolayer N-atom incorporation at Si−SiO2 interfaces in device-quality SiO2 gate oxides has been accomplished by a three-step low-thermal budget process: (i) 300°C remote plasma-assisted oxidation in N2O to form the nitrided Si−SiO2 interface, (ii) 300°C remote plasma-assisted chemical vapor deposition from SiH4 and O2 or N2O to form the oxide layer, and (iii) a 30 s 900°C post-deposition rapid thermal anneal for chemical and structural relaxation. This paper reports on an extension of lowtemperature plasma processing to ultra-thin gate dielectrics (<3 nm) that is based on the first of the three steps identified above: the 300°C remote plasma-assisted oxidation in O2 or N2O. This paper: (i) highlights interrupted processing Auger electron spectroscopy measurements to monitor (a) growth rate and (b) interfacial nitrogen; (ii) discusses the reactions pathways for the plasma-assisted oxide growth process; (iii) contrasts (a) plasma-assisted and (b) furnace and rapid thermal oxidation processes. DA - 1998/1// PY - 1998/1// DO - 10.1016/S0257-8972(97)00389-7 VL - 98 IS - 1-3 SP - 1529-1533 SN - 0257-8972 KW - N-atom KW - Si-SiO2 interfaces KW - plasma-assisted oxidation ER - TY - JOUR TI - Ultrathin nitride/oxide (N/O) gate dielectrics for p(+)-polysilicon gated PMOSFET's prepared by a combined remote plasma enhanced CVD thermal oxidation process AU - Wu, YD AU - Lucovsky, G T2 - IEEE ELECTRON DEVICE LETTERS AB - Ultrathin nitride-oxide (N/O/spl sim/1.5/2.6 nm) dual layer gate dielectrics have been incorporated into PMOSFETs with boron-implanted polysilicon gates. Boron penetration is effectively suppressed by the top plasma-deposited nitride layer leading to improved short channel performance as compared to PMOSFETs with oxide dielectrics. In addition, improved interface characteristics and hot carrier degradation immunity are also demonstrated for the devices with the N/O dual layer gate dielectrics. DA - 1998/10// PY - 1998/10// DO - 10.1109/55.720188 VL - 19 IS - 10 SP - 367-369 SN - 1558-0563 KW - boron penetration KW - gate dielectrics KW - nitride KW - N/O ER - TY - JOUR TI - Thermoplastic elastomer gels. II. Effects of composition and temperature on morphology and gel rheology AU - Laurer, J. H. AU - Mulling, J. F. AU - Khan, Saad AU - Spontak, Richard AU - Lin, J. S. AU - Bukovnik, R. T2 - Journal of Polymer Science. Part B, Polymer Physics DA - 1998/// PY - 1998/// DO - 10.1002/(sici)1099-0488(199810)36:14<2513::aid-polb5>3.3.co;2-6 VL - 36 IS - 14 SP - 2513–2523 ER - TY - JOUR TI - Study of SiOx decomposition kinetics and formation of Si nanocrystals in an SiOx matrix AU - Hinds, B. J. AU - Wang, F. AU - Wolfe, D. M. AU - Hinkle, C. L. AU - Lucovsky, G. T2 - Journal of Non-crystalline Solids DA - 1998/// PY - 1998/// VL - 230 (part A) IS - 1998 May SP - 507-512 ER - TY - JOUR TI - Structural characteristics of AIN films deposited by pulsed laser deposition and reactive magnetron sputtering: A comparative study AU - Jagannadham, K AU - Sharma, AK AU - Wei, Q AU - Kalyanraman, R AU - Narayan, J T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS AB - Aluminum nitride films have been deposited on Si(111) substrates at different substrate temperatures using two techniques; pulsed laser deposition or reactive magnetron sputtering. The films deposited by either of the techniques have been characterized by x-ray diffraction and transmission electron microscopy to determine the crystalline quality, grain size, and epitaxial growth relation with respect to the substrate. The bonding characteristics and the residual stresses present in the films have been evaluated using Raman and Fourier transform infrared spectroscopy. Secondary ion mass spectrometry has been performed to determine the nitrogen stoichiometry and the presence of impurities such as oxygen and silicon. The adhesion strength of the AlN films to the silicon substrate and the wear resistance have been determined by scratch test and a specially designed microscopic wear test. A comparison of the different characteristic features associated with the AlN films deposited by pulsed laser deposition or magnetron sputtering is presented with particular emphasis to electronic and tribological applications. DA - 1998/// PY - 1998/// DO - 10.1116/1.581425 VL - 16 IS - 5 SP - 2804-2815 SN - 0734-2101 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0032370406&partnerID=MN8TOARS ER - TY - JOUR TI - Seasonal variation of hydrographic and nutrient fields during the US JGOFS Arabian Sea Process Study AU - Morrison, JM AU - Codispoti, LA AU - Gaurin, S AU - Jones, B AU - Manghnani, V AU - Zheng, Z T2 - DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY AB - Between September 1994 and December 1995, the US JGOFS Arabian Sea Process Experiment collected extensive, high quality hydrographic data (temperature, salinity, dissolved oxygen and nutrients) during all seasons in the northern Arabian Sea. An analysis of this unique data suite suggests the presence of many features that are described in the canonical literature, but these new data provided the following insights. Although the seasonal evolution of mixed-layer depths was in general agreement with previous descriptions, the deepest mixed-layer depths in our data occurred during the late NE Monsoon instead of the SW Monsoon. The region exhibits considerable mesoscale variability resulting in extremely variable temperature-salinity (TS) distributions in the upper 1000 db. This mesoscale variability is readily observed in satellite imaging, in the high resolution data taken by a companion ONR funded project, and in underway ADCP data. The densest water reaching the sea surface during coastal upwelling appeared to have maximum offshore depths of ∼150 m and σθ’s close to the core value (∼25) for the saline Arabian Sea Water (ASW), but salinities in these upwelling waters were relatively low. The densest water found at the sea surface during late NE Monsoon conditions has σθ’s>24.8 and relatively high salinities, suggesting that they are a source for the ASW salinity maximum. Persian Gulf Water (PGW) with a core σθ of 26.6 forms a widespread salinity maximum. Despite the considerable extent of this feature, Persian Gulf outflow water, with a salinity (4) of ∼39 at its source, can only be a minor contributor. Within the standard US JGOFS sampling grid, maximum salinities on this surface are ∼36.8 at stations near the Gulf, falling to values as low as ∼35.3 at the stations farthest removed from its influence. Even at our standard stations closest to the Gulf (N-1 and N-2), the high-salinity, low-nutrient Persian Gulf water has only a modest direct effect on nutrient concentrations. This PGW salinity maximum is associated with the suboxic portions of the Arabian Sea’s oxygen minimum zone. The salinity maximum associated with Red Sea Water (RSW, core σθ=27.2) in the JGOFS study region is clearly evident at the southermost sampling site at 10′N (S-15). Elsewhere, this signal is weak or absent and salinity on the 27.2 σθ surface tends to increase towards the Persian Gulf, suggesting that the disappearance of this salinity maximum is due, at least in part, to the influence of the Persian Gulf outflow. Inorganic nitrogen-to-phosphate ratios were lower (frequently much lower) than the standard Redfield ratio of 15/1–16/1 (by atoms) at all times and all depths suggesting that inorganic nitrogen was more important than phosphate as a limiting nutrient for phytoplankton growth, and that the effects of denitrification dominated the effects of nitrogen fixation. The water upwelling off the Omani coast during the SW Monsoon has inorganic nitrogen to silicate ratios that were higher (∼2/1) than the ∼1/1 ratio often assumed as the ratio of uptake during diatom growth. The temporal evolution of inorganic nitrogen-to-silicate ratios suggests major alteration by diatom uptake only during the late SW Monsoon cruise (TN050) in August–September 1995. Widespread moderate surface layer nutrient concentrations occurred during the late NE Monsoon. A zone of high offshore nutrient concentrations was encountered during the SW Monsoon, but instead of being associated with offshore upwelling it may represent offshore advection from the coastal upwelling zone, the influence of an eddy, or both. Although our data do not contradict previous suggestions that the volume of subtoxic water may be reduced the SW Monsoon, they suggest a weaker re-oxygenation than indicated by some previous work. Similarly, they do not confirm results suggesting that secondary nitrite maxima may be common in waters with oxygen concentrations >5 μM. DA - 1998/// PY - 1998/// DO - 10.1016/S0967-0645(98)00063-0 VL - 45 IS - 10-11 SP - 2053-2101 SN - 0967-0645 ER - TY - JOUR TI - Reaction pathways for intrinsic and extrinsic defect metastability in light-soaked hydrogenated amorphous silicon - the Staebler-Wronski effect AU - Lucovsky, G. AU - Yang, H. T2 - Journal of Non-crystalline Solids DA - 1998/// PY - 1998/// VL - 230 (part A) IS - 1998 May SP - 281-286 ER - TY - JOUR TI - Plasma-engineered Si-SiO2 interfaces: monolayer nitrogen atom incorporation by low-temperature remote plasma-assisted oxidation in N2O AU - Koh, K AU - Niimi, H AU - Lucovsky, G T2 - SURFACE & COATINGS TECHNOLOGY AB - Abstract This paper presents experimental studies in which N-atoms have been incorporated at Si−SiO 2 interfaces by forming the interface and oxide film by a 300 °C remote plasma-assisted nitridation/oxidation process using N 2 O. Process dynamics have been studied by interrupted plasma processing using on-line Auger electron spectroscopy (AES). Based on the on-line AES, and complementary ex situ secondary ion mass spectroscopy and optical second harmonic generation results, monolayer nitrogen atom interface coverage has been confirmed. The factors that contribute to preferential nitrogen atom attachment at the Si−SiO 2 interface have been identified. DA - 1998/1// PY - 1998/1// DO - 10.1016/S0257-8972(97)00392-7 VL - 98 IS - 1-3 SP - 1524-1528 SN - 0257-8972 KW - Si-SiO2 interfaces KW - N-atoms KW - N2O KW - Auger electron spectroscopy ER - TY - JOUR TI - Piezoelectric measurements with atomic force microscopy AU - Christman, JA AU - Woolcott, RR AU - Kingon, AI AU - Nemanich, RJ T2 - APPLIED PHYSICS LETTERS AB - An atomic force microscope (AFM) is used to measure the magnitude of the effective longitudinal piezoelectric constant (d33) of thin films. Measurements are performed with a conducting diamond AFM tip in contact with a top electrode. The interaction between the tip and electric field present is a potentially large source of error that is eliminated through the use of this configuration and the conducting diamond tips. Measurements yielded reasonable piezoelectric constants of X-cut single-crystal quartz, thin film ZnO, and nonpiezoelectric SiO2 thin films. DA - 1998/12/28/ PY - 1998/12/28/ DO - 10.1063/1.122914 VL - 73 IS - 26 SP - 3851-3853 SN - 0003-6951 ER - TY - JOUR TI - Phase control of MoxN films via chemical vapor deposition AU - Roberson, SL AU - Finello, D AU - Davis, RF T2 - THIN SOLID FILMS AB - Polycrystalline single phase (γ-Mo2N and δ-MoN) and two phase (γ-Mo2N+δ-MoN) films have been deposited via chemical vapor deposition on prepared 50 μm thick polycrystalline Ti substrates using both molybdenum pentachloride (MoCl5) and molybdenum hexacarbonyl (Mo(CO)6), diluted in either N2 or Ar, and anhydrous ammonia (NH3) in a cold-wall, vertical pancake-style reactor. X-ray diffraction data showed that polycrystalline, single phase γ-Mo2N films were deposited between 400–450°C with the MoCl5 precursor and between 350–500°C with the Mo(CO)6 precursor. Above these respective temperatures and up to 700°C, a two-phase mixture of γ-Mo2N and δ-MoN was observed. At 700°C, single phase δ-MoN films were deposited by employing the Mo(CO)6 precursor and 1.5 slm of NH3; however, a two phase mixture of ≈95 at.% δ-MoN and ≈5 at.% γ-Mo2N was observed in films prepared using the MoCl5 precursor. Regardless of the precursor, decreases in the NH3 flow rate were matched by decreases in δ-MoN percentages at each temperature where δ-MoN was present. Increasing in the deposition rate also resulted in decreasing δ-MoN percentages at each deposition temperature. Scanning electron micrographs (SEM) indicated that the porous microstructure of the films were dependent on both the deposition temperature and the precursor employed. Energy dispersive X-ray (EDX) data indicated that films deposited at and above 400°C with the MoCl5 precursor did not contain detectable levels of chlorine. Higher carbon levels were detected in films deposited with the Mo(CO)6 precursor than with the MoCl5 precursor. DA - 1998/7/1/ PY - 1998/7/1/ DO - 10.1016/S0040-6090(97)01202-9 VL - 324 IS - 1-2 SP - 30-36 SN - 0040-6090 KW - MoxN films KW - phase control KW - chemical vapor deposition ER - TY - JOUR TI - Optical characterization of GaAs/AlAs short period superlattices AU - Woo, DH AU - Han, IK AU - Choi, WJ AU - Lee, S AU - Kim, HJ AU - Lee, JI AU - Kim, SH AU - Kang, KN AU - Choi, SG AU - Kim, YD AU - Yoo, SD AU - Aspnes, DE AU - Rhee, SJ AU - Woo, JC T2 - MICROELECTRONIC ENGINEERING AB - We present optical studies of a series of GaAs/AlAs short period superlattices grown by molecular beam epitaxy. The structural properties were examined by X-ray diffraction measurements. The quantum confinement of the electronic and the vibronic states were observed in the low temperature photoluminescence and Raman scattering experiments, respectively. Spectroscopic ellipsometric (SE) measurements were also performed. We found a new structure at the lower E2 peak, which is the best resolution of the E2 structure in these SLs so far obtained by SE. DA - 1998/8// PY - 1998/8// DO - 10.1016/S0167-9317(98)00173-7 VL - 43-4 IS - 1998 Aug. SP - 265-270 SN - 0167-9317 ER - TY - JOUR TI - Molecular beam epitaxy growth and properties of GaN, InGaN, and GaN/InGaN quantum well structures AU - Johnson, MAL AU - Brown, JD AU - El-Masry, NA AU - Cook, JW AU - Schetzina, JF AU - Kong, HS AU - Edmond, JA T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Growth of III–V nitrides by molecular beam epitaxy (MBE) was studied using rf nitrogen plasma sources. Plasma sources from three different vendors have been tested. All three of the sources have been used to grow high quality GaN. However, the EPI rf source produces an optical emission spectrum that is very rich in the active nitrogen species of 1st-positive excited nitrogen molecules and nitrogen atoms. GaN growth rates at 800 °C of 1 μm/h have been achieved using this source. The MBE-grown GaN films are deposited homoepitaxially on high quality metalorganic vapor phase epitaxy-grown GaN/SiC substrates. With the growth conditions for high quality undoped GaN as a base line, a detailed study of Mg doping for p-type GaN was performed. An acceptor incorporation of 2×1019 cm−3 was measured by both capacitance–voltage and secondary ion mass spectroscopy for a doping source temperature of 290 °C. However, a faceted three-dimensional growth mode was observed by reflection high energy electron diffraction during Mg doping of GaN. Additional studies suggest an interdependence between Mg incorporation and growth surface morphology. Quantum well structures made from the InGaN ternary alloy were grown using a modulated beam MBE method. With this technique, quantum well compositions were controllable, grown with visible luminescence ranging from 400 to 515 nm depending on indium mole fraction. Light emitting diode test structures, combining Mg p-type doping with InGaN quantum wells, were fabricated and tested. DA - 1998/// PY - 1998/// DO - 10.1116/1.590000 VL - 16 IS - 3 SP - 1282-1285 SN - 1071-1023 ER - TY - JOUR TI - Mixtures of polymer tails and loops grafted to an impenetrable interface AU - Driscoll, DC AU - Gulati, HS AU - Spontak, RJ AU - Hall, CK T2 - POLYMER AB - Property modification of an inorganic surface can be readily achieved through the use of macromolecules chemically grafted to the surface at specific functional sites along the chain. While numerous efforts have addressed the properties of linear chains grafted at one end (tails), relatively few have extended such studies to include double-tethered chains (loops). In this work, we consider loop/tail mixtures in which both chain species possess an identical number of repeat units. Bond-fluctuation simulations have been performed to ascertain the effects of composition, chain length and surface density on the segmental density distribution and layer height of each constituent species and of the mixture. These results compare favourably with self-consistent field predictions for bidisperse mixtures of grafted tails differing in length by a factor of two. DA - 1998/12// PY - 1998/12// DO - 10.1016/S0032-3861(97)10122-7 VL - 39 IS - 25 SP - 6339-6346 SN - 1873-2291 KW - bond-fluctuation model KW - grafted polymers KW - brushes ER - TY - JOUR TI - Minimization of dangling bond defects in hydrogenated silicon nitride dielectrics for thin film transistors (TFTs) AU - Lucovsky, G. AU - Phillips, J. C. T2 - Journal of Non-crystalline Solids DA - 1998/// PY - 1998/// VL - 230 (part B) IS - 1998 SP - 1221-1225 ER - TY - JOUR TI - Mechanism of iron gettering in MeV Si ion implanted epitaxial silicon AU - Koveshnikov, SV AU - Rozgonyi, GA T2 - JOURNAL OF APPLIED PHYSICS AB - The gettering properties of the two damage regions, namely, a near-surface vacancy-rich region, Rp/2 and a buried layer of extended defects near the MeV Si ion projected range, Rp, have been quantitatively determined by means of secondary ion mass spectrometry and deep level transient spectroscopy techniques. To isolate the simultaneous and competitive gettering between iron and oxygen, the MeV defects were introduced into epitaxial silicon doped with boron. Czochralski Si samples were also used for comparison. Experiments on isochronal and isothermal annealing of Fe contaminated samples in conjunction with the rapid quenching procedure allowed us to establish the dominating gettering mechanisms in the two damage regions. Thus, gettering in the Rp region was driven by relaxation of supersaturated Fe, while the segregation-induced gettering mechanism was operative in the Rp/2 zone. As a result, the concentration of Fe, which was remained ungettered at elevated temperature, was well below the solid solubility limit. The major gettering parameters of MeV defects, such as gettering capacity, efficiency, and thermal stability have been determined. DA - 1998/9/15/ PY - 1998/9/15/ DO - 10.1063/1.368462 VL - 84 IS - 6 SP - 3078-3084 SN - 0021-8979 ER - TY - JOUR TI - Lattice site location studies of ion implanted Li-8 in GaN AU - Dalmer, M AU - Restle, M AU - Sebastian, M AU - Vetter, U AU - Hofsass, H AU - Bremser, MD AU - Ronning, C AU - Davis, RF AU - Wahl, U AU - Bharuth-Ram, K T2 - JOURNAL OF APPLIED PHYSICS AB - The lattice sites of ion implanted Li atoms in GaN were studied as a function of implantation temperature between room temperature and 770 K. We measured the channeling and blocking patterns of α-particles emitted in the radioactive decay of implanted Li8 ions to determine the Li lattice sites. Below 700 K Li atoms occupy mainly interstitial sites in the center of the c-axis hexagons at positions c/4 and 3c/4, where c is the lattice constant in c-axis direction. Around 700 K Li starts to diffuse and presumably interacts with vacancies created in the implantation process. This leads to the formation of substitutional Li above 700 K. An activation energy of about 1.7 eV for interstitial Li diffusion was determined. DA - 1998/9/15/ PY - 1998/9/15/ DO - 10.1063/1.368463 VL - 84 IS - 6 SP - 3085-3089 SN - 1089-7550 ER - TY - JOUR TI - Ir and Ru bottom electrodes for (Ba, Sr) TiO3 thin films deposited by liquid delivery source chemical vapor deposition AU - Lee, WJ AU - Basceri, C AU - Streiffer, SK AU - Kingon, AI AU - Yang, DY AU - Park, Y AU - Kim, HG T2 - THIN SOLID FILMS AB - The electrical properties and surface morphologies of (Ba, Sr)TiO3 thin films, with various bottom electrode structures, deposited by liquid delivery metal organic chemical vapor deposition were investigated. Ir and Ru films as a bottom electrode with varying deposition temperatures were prepared onto SiO2 and polySi substrate structures using ion beam sputtering technique. It is observed that electrical properties of BST films deposited by liquid delivery MOCVD was changed with the deposition temperatures of Ir and Ru as well as substrate structures. Furthermore, it is revealed that these variations in leakage current could be strongly related with the roughness of BST films. DA - 1998/6/22/ PY - 1998/6/22/ DO - 10.1016/S0040-6090(97)01043-2 VL - 323 IS - 1-2 SP - 285-290 SN - 0040-6090 KW - liquid delivery KW - bottom electrode structures KW - chemical vapor deposition ER - TY - JOUR TI - Investigation of optically active E-1 transversal optic phonon modes in AlxGa1-xN layers deposited on 6H-SiC substrates using infrared reflectance AU - Wisniewski, P AU - Knap, W AU - Malzac, JP AU - Camassel, J AU - Bremser, MD AU - Davis, RF AU - Suski, T T2 - APPLIED PHYSICS LETTERS AB - We report an investigation, performed in the full composition range x=0–1, of the change in infrared reflectivity spectra of AlxGa1−xN layers deposited on 6H–SiC substrates. We have found two different transverse E1(TO) phonon frequencies that can be assigned to AlN-like and GaN-like modes. The composition dependences of these frequencies can be well approximated by linear functions and the oscillator strengths scale like the corresponding Al and Ga mole fractions, respectively. On a purely experimental basis, this establishes evidence of a two-mode behavior for this controversial alloy system. The frequencies of the impurity mode of Ga in AlN (622 cm−1) and of the impurity mode of Al in GaN (643 cm−1) were determined. DA - 1998/9/28/ PY - 1998/9/28/ DO - 10.1063/1.122273 VL - 73 IS - 13 SP - 1760-1762 SN - 1077-3118 ER - TY - JOUR TI - Field emission energy distribution analysis of cubic-BN-coated Mo emitters: Nonlinear behavior AU - McCarson, BL AU - Schlesser, R AU - Sitar, Z T2 - JOURNAL OF APPLIED PHYSICS AB - Voltage-dependent field emission energy distribution (V-FEED) and current versus voltage measurements were performed on Mo tips coated with intrinsic cubic boron nitride (c-BN) to determine the origin of the field-emitted electrons. Spectra were collected from the Mo emitters under ultrahigh vacuum conditions both before and after being coated. In some instances multiple FEED peaks were observed in the collected spectra. These corresponded to multiple emission sites on the emitter. The energy of the field-emitted electrons from the c-BN-coated emitters usually depended linearly upon the applied voltage and could be explained using a simplified band-bending model. However, at higher voltages the FEED measured from the c-BN-coated emitters departed from this linear behavior. These nonlinearities were attributed to a contact resistance at the Mo/c-BN interface which had a greater influence on the energy distribution of emitted electrons at larger emission currents. DA - 1998/9/15/ PY - 1998/9/15/ DO - 10.1063/1.368496 VL - 84 IS - 6 SP - 3382-3385 SN - 1089-7550 ER - TY - JOUR TI - Electric field strengthening during superplastic creep of Zn-5 wt% Al: A negative electroplastic effect AU - Li, SC AU - Conrad, H T2 - SCRIPTA MATERIALIA AB - The effect of an electric field on the microstructure and mechanical properties of an Al-Cu-Li alloy was investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), microhardness tests, electric conductivity tests, and tensile tests. The results show that the field-aged sample exhibited a shorter stable hardening plateau period and an earlier peak-aged stage than the field-free-aged sample. Also, the hardness and conductivity of the field-aged sample during the hardening plateau interval were generally greater than that of the field-free-aged sample. This might be due to the fact that the electric field promoted the precipitation of the β'/δ' phase and accelerated the growth of the θ' phase. The improvement in mechanical properties of the field-aged sample was caused by the segregation of the T1 phase at the subgrain boundaries and the grain boundaries. A vacancy-atom complex diffusion model successfully explains the microstructure evolution and the change in mechanical properties of the alloy during the ageing process accompanied by an electric field. DA - 1998/9/4/ PY - 1998/9/4/ DO - 10.1016/S1359-6462(98)00268-1 VL - 39 IS - 7 SP - 847-851 SN - 1359-6462 ER - TY - JOUR TI - Effect of temperature on mechanical anisotropy of Zircaloy-4 sheet AU - Wang, Y AU - Murty, KL T2 - METALS AND MATERIALS-KOREA DA - 1998/// PY - 1998/// DO - 10.1007/bf03026387 VL - 4 IS - 4 SP - 723-726 SN - 1225-9438 KW - Zircaloy KW - anisotropy KW - R parameter KW - P parameter KW - grid test ER - TY - JOUR TI - Controlled nitrogen incorporation at Si-SiO2 interfaces by remote plasma-assisted processing AU - Koh, K AU - Niimi, H AU - Lucovsky, G AU - Green, ML T2 - JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS AB - This paper presents experimental studies in which N-atoms have been incorporated at Si–SiO 2 interfaces by forming the interface and oxide film by a 300°C remote plasma assisted nitridation/oxidation process using N 2 O. Process dynamics have been studied by on-line Auger electron spectroscopy (AES) by interrupted plasma processing. Based on AES studies using N 2 O, O 2 and sequenced N 2 O and O 2 source gases, reaction pathways for i) N-atom incorporation at and/or ii) removal from buried Si–SiO 2 interfaces have been identified, and contrasted with reaction pathways for nitridation using conventional furnace processing. DA - 1998/2// PY - 1998/2// DO - 10.1143/JJAP.37.709 VL - 37 IS - 2 SP - 709-714 SN - 0021-4922 KW - low-temperature processing KW - plasma-assisted oxidation and nitridation KW - rapid thermal annealing KW - Si-SiO2 interfaces KW - Auger electron spectroscopy KW - optical second harmonic generation KW - chemical reaction pathways ER - TY - JOUR TI - Biaxial strain in AlxGa1-xN/GaN layers deposited on 6H-SiC AU - Perry, WG AU - Bremser, MB AU - Zheleva, T AU - Linthicum, KJ AU - Davis, RF T2 - THIN SOLID FILMS AB - AlxGa1−xN/GaN multilayers (x≤0.12) deposited on AlN(0001) buffer layer/6H-SiC(0001) substrate combinations have been investigated using high resolution X-ray diffraction. Rocking curves (ω) showed that the AlxGa1−xN layers in the main contained a reduced dislocation density relative to the underlying GaN layers. The line widths of the radial scans (2θ−ω) of the AlxGa1−xN layers increased as the Al mole fraction increased due to alloy broadening. The in-plane lattice constant (a) of the AlxGa1−xN layer for each sample was equivalent to that of the GaN layer, indicating the layers were coherently strained. The strain in the AlGaN layer was tensile for each sample. This was determined using high-resolution reciprocal space maps of the (015) and (024) planes which revealed that the AlxGa1−xN and GaN lattice points had the same value of the in-plane components of the reciprocal lattice vector (S̄‖). For higher Al mole fractions, the samples were severely cracked, indicating the strain in the AlxGa1−xN layers exceeded critical values. DA - 1998/7/1/ PY - 1998/7/1/ DO - 10.1016/S0040-6090(97)01217-0 VL - 324 IS - 1-2 SP - 107-114 SN - 0040-6090 KW - high resolution X-ray diffraction KW - in-plane components KW - reciprocal lattice vector ER - TY - JOUR TI - Atomic structure and thermal stability of silicon suboxides in bulk thin films and in transition regions at Si-SiO2 interfaces AU - Lucovsky, G. T2 - Journal of Non-crystalline Solids DA - 1998/// PY - 1998/// VL - 230 (part A) IS - 1998 May SP - 1-14 ER - TY - JOUR TI - An investigation of the deformation mechanisms in Sn5%Sb alloy using tensile, creep and ABI tests from ambient to 473K AU - Murty, KL AU - Mathew, MD AU - Haggag, FM T2 - METALS AND MATERIALS-KOREA DA - 1998/// PY - 1998/// DO - 10.1007/bf03026401 VL - 4 IS - 4 SP - 799-802 SN - 1225-9438 KW - ABI KW - Sn5%Sb KW - creep KW - activation energy KW - deformation mechanism ER - TY - JOUR TI - Advection of upwelled waters in the form of plumes off Oman during the Southwest Monsoon AU - Manghnani, V AU - Morrison, JM AU - Hopkins, TS AU - Bohm, E T2 - DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY AB - Advanced Very High Resolution Radiometer (AVHRR) imagery of sea-surface-temperature, TOPEX/POSEIDON measurements of sea-level-anomaly (SLA), and modeled surface winds and wind-stress fields are used in concert with other ancillary data to describe the influence of the 1995 Southwest Monsoon on the distribution of upwelled waters off the coast of Oman. The Oman upwelling zone is characterized by the entrainment of cold upwelled waters into plumes extending from the coast into the deep ocean unaffected by the steep bottom gradients. The most prominent of these plumes is found offshore of Ras al Madraka. A mechanism for the entrainment of upwelled water into plumes is hypothesized, and validated by observational data. It is proposed that the location of the plume is primarily governed by the sea level structure away from the coast and that coastally upwelled water is passively advected offshore through regions of low sea level. Analysis of the surface wind-stress fields show significant spatial variability associated with the predominantly cyclonic mean wind-stress curl, with relatively weak curl observed in the region south of Ras al Madraka and north of Ras Marbat. Decomposition of the surface wind-stress fields through Principal Component Analysis shows that, at certain periods, the development of strong along-shore winds and cyclonic wind-stress curl in the region north of Ras al Madraka. This information, combined with concurrent observations of TOPEX/POSEIDON sea-level-anomalies (SLAs), satellite derived sea-surface-temperatures (SST), and surface current measurements, shows that the combined effects of a strong along-shore wind field and positive wind-stress curl forces a depression in sea level in the region north of Ras al Madraka. The sea level gradient, caused by the presence of a sustained high sea level to the south of Ras al Madraka, causes geostrophic advection of coastally upwelled waters away from the shelf. Acoustic Doppler Current Profiler (ADCP) velocity measurements along with SST maps further prove that the upwelled water is geostrophically advected offshore as opposed to being an offshore deflection of a wind-driven coastal current. Comparison of interannual features in the TOPEX/POSEIDON SLAs suggest that the plumes coming off coast in the Oman upwelling zone may not be directly linked to the coastal topography or bathymetry but are a result of interaction between mesoscale variations in the wind field and the underlying ocean. The strong along-shore winds and cyclonic wind-stress curl to the north of Ras al Madraka becomes enhanced when the Findlater Jet moves closer to the Oman coast than its mean position. DA - 1998/// PY - 1998/// DO - 10.1016/S0967-0645(98)00062-9 VL - 45 IS - 10-11 SP - 2027-2052 SN - 0967-0645 ER - TY - JOUR TI - Acceptor and donor doping of AlxGa1-xN thin film alloys grown on 6H-SiC(0001) substrates via metalorganic vapor phase epitaxy AU - Bremser, MD AU - Perry, WG AU - Nam, OH AU - Griffis, DP AU - Loesing, R AU - Ricks, DA AU - Davis, RF T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 1998/4// PY - 1998/4// DO - 10.1007/s11664-998-0392-9 VL - 27 IS - 4 SP - 229-232 SN - 0361-5235 KW - 6H-SiC(0001) KW - acceptor doping KW - AlxGa1-xN KW - GaN KW - charge scattering KW - donor doping KW - electron mobility ER - TY - JOUR TI - Ultrathin oxide-nitride gate dielectric MOSFET's AU - Parker, CG AU - Lucovsky, G AU - Hauser, , JR T2 - IEEE ELECTRON DEVICE LETTERS AB - The first ultrathin oxide-nitride (O-N) gate dielectrics with oxide equivalent thickness of less than 2 nm have been deposited and characterized in n-MOSFET's. The O-N gates, deposited by remote plasma-enhanced CVD, demonstrate reduced gate leakage when compared with oxides of equivalent thickness while retaining comparable drive currents. DA - 1998/4// PY - 1998/4// DO - 10.1109/55.663529 VL - 19 IS - 4 SP - 106-108 SN - 0741-3106 ER - TY - JOUR TI - Triblock copolymer/homopolymer blends: Conformational changes, microstructural transition and macrophase separation AU - Norman, DA AU - Kane, L AU - White, SA AU - Smith, SD AU - Spontak, RJ T2 - JOURNAL OF MATERIALS SCIENCE LETTERS DA - 1998/4/1/ PY - 1998/4/1/ DO - 10.1023/A:1006565418979 VL - 17 IS - 7 SP - 545-549 SN - 0261-8028 ER - TY - JOUR TI - The role of defects on thermophysical properties: thermal expansion of V, Nh, Ta, Mo and W AU - Wang, K AU - Reeber, RR T2 - MATERIALS SCIENCE & ENGINEERING R-REPORTS AB - Thermophysical properties at high temperatures and pressures are difficult to measure. Many reviews have approximated experimental data with empirical polynomial functions. In the case of thermal expansion and molar volume, extensive results for refractory body centered cubic (BCC) metals have been published. A critical evaluation of these experimental data is essential for many other studies. We provide this evaluation in terms of models that interrelate the thermophysical properties, self diffusion, and high temperature thermal defects. Experimental and theoretical methods for measuring and representing thermal expansion and the limitations of such methods are also briefly reviewed. Results for V, Nb, Ta, Mo, and W fall into two distinct subgroups relating to their elemental positions in the periodic table. The thermal expansions for these elements are analyzed within the constraints of a simple vibrational model and its equation of state. This approach represented the thermal expansion as the contributions from a perfect crystal and the crystal's high temperature anharmonicity as well as its thermal defects. Quantitative expressions, neglecting electronic contributions, are provided for the coefficient of thermal expansion and the expansivities for these five BCC metals from near 20°K to their melting temperatures. Vacancy formation enthalpies and entropies are also estimated. Our vacancy thermodynamic results are compared with earlier predictions and results from positron annihilation, thermal expansion, and specific heat measurements. DA - 1998/7/15/ PY - 1998/7/15/ DO - 10.1016/S0927-796X(98)00011-4 VL - 23 IS - 3 SP - 101-137 SN - 0927-796X ER - TY - JOUR TI - The formation of crystalline defects and crystal growth mechanism in InxGa1-xN/GaN heterostructure grown by metalorganic vapor phase epitaxy AU - Kawaguchi, Y. AU - Shimizu, M. AU - Yamaguchi, M. AU - Hiramatsu, K. AU - Sawaki, N. AU - Taki, W. AU - Tsuda, H. AU - Kuwano, N. AU - Oki, K. AU - Zheleva, T. AU - Davis, R. F. T2 - Journal of Crystal Growth DA - 1998/// PY - 1998/// VL - 190 IS - 1998 June SP - 24-28 ER - TY - JOUR TI - Synthesis of low oxygen concentration molybdenum nitride films AU - Roberson, S. L. AU - Finello, D. AU - Davis, R. F. T2 - Materials Science & Engineering. A, Structural Materials: Properties, Microstructure and Processing DA - 1998/// PY - 1998/// VL - 248 IS - 1-2 SP - 198-205 ER - TY - JOUR TI - Structure and properties of rapid thermal chemical vapor deposited polycrystalline silicon-germanium films on SiO2 using Si2H6, GeH4, and B2H6 gases AU - Li, VZQ AU - Mirabedini, MR AU - Hornung, BE AU - Heinisch, HH AU - Xu, M AU - Batchelor, D AU - Maher, DM AU - Wortman, JJ AU - Kuehn, RT T2 - JOURNAL OF APPLIED PHYSICS AB - Deposition of undoped and in situ boron-doped polycrystalline silicon-germanium (poly-Si1−xGex) films on oxide has been investigated at temperatures below 625 °C and a pressure of 4 Torr in a rapid thermal chemical vapor deposition system. The influences of reactant gases such as Si2H6, SiH4, GeH4, and B2H6 on the nucleation behavior, and structural properties of poly-Si1−xGex films formed on oxide were studied. The experimental results showed that in situ boron-doped or undoped poly-Si1−xGex films can be directly deposited on oxide without an initial Si predeposition layer to provide the necessary nucleation sites on the surface when using Si2H6 as the Si source gas. However, when SiH4 was used as the Si source gas, only in situ boron-doped films can be deposited nonselectively on the oxide without the initial Si predeposition layer, and to deposit undoped poly-Si1−xGex films, Si predeposition is needed, otherwise Si1−xGex islands are formed on the oxide. X-ray diffraction analysis showed that poly-Si1−xGex films deposited using Si2H6, GeH4, and B2H6 gas mixture have three singular peaks corresponding to {311}, {220}, and {111} planes, thus indicating the Si1−xGex alloy is formed. In addition, we found that B2H6 gas has a minor effect on the Ge incorporation into the films but reduces the overall deposition rate. DA - 1998/5/15/ PY - 1998/5/15/ DO - 10.1063/1.367404 VL - 83 IS - 10 SP - 5469-5476 SN - 0021-8979 ER - TY - JOUR TI - Shear strength of electrorheological particle clusters AU - Wu, CW AU - Conrad, H T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - The electrorheological shear strength of clusters of small, humidified glass spheres with an average diameter ∼220 μm in silicone oil forming a rectangular or cubic lattice was determined with d.c. electrical field. The arrangement, shearing, and the yield and fracture processes of the clusters were observed. The shear strength of the cluster increased with the number of chains in a cluster and with the applied electrical field. The shear modulus was essentially independent of the number of chains in a cluster, but increased with applied field. DA - 1998/6/15/ PY - 1998/6/15/ DO - 10.1016/s0921-5093(98)00497-3 VL - 248 IS - 1-2 SP - 161-164 SN - 0921-5093 KW - electrorheological particle clusters KW - shear strength KW - shear modulus ER - TY - JOUR TI - Self-aligned gate and source drain contacts in inverted-staggered a-Si : H thin-film transistors fabricated using selective area silicon PECVD AU - Yang, CS AU - Read, WW AU - Arthur, C AU - Srinivasan, E AU - Parsons, GN T2 - IEEE ELECTRON DEVICE LETTERS AB - This article demonstrates full self-aligned inverted-staggered amorphous silicon thin-film transistors (TFT's) fabricated using selective plasma deposition of doped microcrystalline silicon source/drain contacts. Back-side exposure, using the bottom metal gate as the mask, produced the self-aligned contact openings. Selective deposition of the n+ silicon contact layer assures self-aligned ion resistance contacts and eliminates the need for reactive ion etching of the n+ silicon. Complete TFT fabrication requires no critical alignment steps. Transistors have linear mobility between 0.6 and 1.1 cm/sup 2//Vs, threshold voltage of 3.0 V, and sub-threshold slope of 0.35 V/decade. The OFF current is <10/sup -11/ A with -10 V gate voltage and 10 V between the source and drain, and ON/OFF ratios exceed 10. DA - 1998/6// PY - 1998/6// DO - 10.1109/55.678536 VL - 19 IS - 6 SP - 180-182 SN - 0741-3106 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000073727100002&KeyUID=WOS:000073727100002 ER - TY - JOUR TI - Samarium cobalt phase equilibria revisited; Relevance to permanent magnets AU - Stadelmaier, H. H. AU - Reinsch, B. AU - Petzow, G. T2 - Zeitschrift fur MetallkundeAmerican Journal of Physiology DA - 1998/// PY - 1998/// VL - 89 IS - 2 SP - 114-118 ER - TY - JOUR TI - Resistance degradation behavior of Ba0.7Sr0.3TiO3 thin films compared to mechanisms found in titanate ceramics and single crystals AU - Grossmann, M. AU - Hoffmann, S. AU - Gusowski, S. AU - Waser, R. AU - Streiffer, S. K. AU - Basceri, C. AU - Parker, C. B. AU - Lash, S. E. AU - Kingon, A. I. T2 - Integrated Ferroelectrics DA - 1998/// PY - 1998/// VL - 22 IS - 1-4 SP - 603-614 ER - TY - JOUR TI - Pinholes, dislocations and strain relaxation in InGaN AU - Jahnen, B. AU - Albrecht, M. AU - Dorsch, W. AU - Christiansen, S. AU - Strunk, H. P. AU - Hanser, D. AU - Davis, R. F. T2 - MRS Internet Journal of Nitride Semiconductor Research DA - 1998/// PY - 1998/// VL - 3 IS - 39 ER - TY - JOUR TI - Novel developmentally regulated phosphoinositide binding proteins from soybean whose expression bypasses the requirement for an essential phosphatidylinositol transfer protein in yeast AU - Kearns, MA AU - Monks, DE AU - Fang, M AU - Rivas, MP AU - Courtney, PD AU - Chen, J AU - Prestwich, GD AU - Theibert, AB AU - Dewey, RE AU - Bankaitis, VA T2 - EMBO JOURNAL AB - Article15 July 1998free access Novel developmentally regulated phosphoinositide binding proteins from soybean whose expression bypasses the requirement for an essential phosphatidylinositol transfer protein in yeast M. A. Kearns M. A. Kearns Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL, 35294-0005 USA Search for more papers by this author D. E. Monks D. E. Monks Department of Crop Science, North Carolina State University, Raleigh, NC, 27695-7620 USA Search for more papers by this author M. Fang M. Fang Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL, 35294-0005 USA Search for more papers by this author M. P. Rivas M. P. Rivas Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL, 35294-0005 USA Search for more papers by this author P. D. Courtney P. D. Courtney Department of Crop Science, North Carolina State University, Raleigh, NC, 27695-7620 USA Search for more papers by this author J. Chen J. Chen Department of Medicinal Chemistry, College of Pharmacy, University of Utah, Salt Lake City, UT, 84112-5820 USA Search for more papers by this author G. D. Prestwich G. D. Prestwich Department of Medicinal Chemistry, College of Pharmacy, University of Utah, Salt Lake City, UT, 84112-5820 USA Search for more papers by this author A. B. Theibert A. B. Theibert Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294-0005 USA Search for more papers by this author R. E. Dewey R. E. Dewey Department of Crop Science, North Carolina State University, Raleigh, NC, 27695-7620 USA Search for more papers by this author V. A. Bankaitis Corresponding Author V. A. Bankaitis Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL, 35294-0005 USA Search for more papers by this author M. A. Kearns M. A. Kearns Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL, 35294-0005 USA Search for more papers by this author D. E. Monks D. E. Monks Department of Crop Science, North Carolina State University, Raleigh, NC, 27695-7620 USA Search for more papers by this author M. Fang M. Fang Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL, 35294-0005 USA Search for more papers by this author M. P. Rivas M. P. Rivas Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL, 35294-0005 USA Search for more papers by this author P. D. Courtney P. D. Courtney Department of Crop Science, North Carolina State University, Raleigh, NC, 27695-7620 USA Search for more papers by this author J. Chen J. Chen Department of Medicinal Chemistry, College of Pharmacy, University of Utah, Salt Lake City, UT, 84112-5820 USA Search for more papers by this author G. D. Prestwich G. D. Prestwich Department of Medicinal Chemistry, College of Pharmacy, University of Utah, Salt Lake City, UT, 84112-5820 USA Search for more papers by this author A. B. Theibert A. B. Theibert Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294-0005 USA Search for more papers by this author R. E. Dewey R. E. Dewey Department of Crop Science, North Carolina State University, Raleigh, NC, 27695-7620 USA Search for more papers by this author V. A. Bankaitis Corresponding Author V. A. Bankaitis Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL, 35294-0005 USA Search for more papers by this author Author Information M. A. Kearns1, D. E. Monks2, M. Fang1, M. P. Rivas1, P. D. Courtney2, J. Chen3, G. D. Prestwich3, A. B. Theibert4, R. E. Dewey2 and V. A. Bankaitis 1 1Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL, 35294-0005 USA 2Department of Crop Science, North Carolina State University, Raleigh, NC, 27695-7620 USA 3Department of Medicinal Chemistry, College of Pharmacy, University of Utah, Salt Lake City, UT, 84112-5820 USA 4Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294-0005 USA *Corresponding author. E-mail: [email protected] The EMBO Journal (1998)17:4004-4017https://doi.org/10.1093/emboj/17.14.4004 PDFDownload PDF of article text and main figures. ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InMendeleyWechatReddit Figures & Info Phosphatidylinositol transfer proteins (PITPs) have been shown to play important roles in regulating a number of signal transduction pathways that couple to vesicle trafficking reactions, phosphoinositide-driven receptor-mediated signaling cascades, and development. While yeast and metazoan PITPs have been analyzed in some detail, plant PITPs remain entirely uncharacterized. We report the identification and characterization of two soybean proteins, Ssh1p and Ssh2p, whose structural genes were recovered on the basis of their abilities to rescue the viability of PITP-deficient Saccharomyces cerevisiae strains. We demonstrate that, while both Ssh1p and Ssh2p share ∼25% primary sequence identity with yeast PITP, these proteins exhibit biochemical properties that diverge from those of the known PITPs. Ssh1p and Ssh2p represent high-affinity phosphoinositide binding proteins that are distinguished from each other both on the basis of their phospholipid binding specificities and by their substantially non-overlapping patterns of expression in the soybean plant. Finally, we show that Ssh1p is phosphorylated in response to various environmental stress conditions, including hyperosmotic stress. We suggest that Ssh1p may function as one component of a stress response pathway that serves to protect the adult plant from osmotic insult. Introduction Phosphatidylinositol/phosphatidylcholine transfer proteins (PITPs) transfer either phosphatidylinositol (PI) or phosphatidylcholine (PC) between membrane bilayers in vitro (Cleves et al., 1991a; Wirtz, 1991), and this class of proteins exhibits two hallmark features of interest. First, PITPs are unique in that while these polypeptides contain one phospholipid (PL) binding site per protein monomer, PITPs have the ability to accommodate binding of two dissimilar PLs (PI and PC) in a mutually exclusive binding reaction. Secondly, PITPs exhibit a high level of primary sequence conservation. These homologies among PITPs are presently bifurcated into two distinct branches. PITPs of mammalian and insect origin share at least 40% primary sequence identity (Dickeson et al., 1989; Vihtelic et al., 1993; Tanaka and Hosaka, 1994; Chang et al., 1997). Fungal PITPs are also highly similar to each other at the primary sequence level (Bankaitis et al., 1989, 1990; Salama et al., 1990; Lopez et al., 1994), but share no primary sequence similarity with metazoan PITPs (Bankaitis et al., 1989; Dickeson et al., 1989; Vihtelic et al., 1993). The Saccharomyces cerevisiae SEC14 gene product (Sec14p) represents the major PITP of yeast, and plays an essential role in protein exit from the yeast Golgi complex (Bankaitis et al., 1989, 1990). A dissection of how Sec14p translates its PI/PC-exchange activity to biological function has been driven by the characterization of mutations that relieve cells of the normally essential Sec14p requirement for Golgi function and cell viability (Cleves et al., 1989, 1991b; Alb et al., 1996; Fang et al., 1996). Characterization of these ‘bypass Sec14p’ mutations has generated the proposal that Sec14p maintains the integrity of a critical Golgi diacylglycerol (DAG) pool that is required for Golgi secretory function (McGee et al., 1994; Kearns et al., 1997). An important aspect of this function is the ability of the PC-bound form of Sec14p to repress the activity of the CDP-choline pathway for PC biosynthesis (a potent DAG consumer) in yeast Golgi membranes (McGee et al., 1994; Skinner et al., 1995). The PI-bound form of Sec14p may function independently in potentiating PI metabolism in an action which would resupply the Golgi DAG pool. This mode of action is inferred from the demonstration that accelerated PI-turnover represents one in vivo mechanism for effecting a ‘bypass Sec14p’ phenotype (Kagiwada et al., 1996; Kearns et al., 1997), that the PI-transfer activity of mammalian PITP is necessary for rescue of Sec14p defects (Alb et al., 1995), and that both Sec14p and mammalian PITPs stimulate PI-metabolism in phosphoinositide-dependent reactions that have been reconstituted in permeabilized mammalian cells (Hay and Martin, 1993; Thomas et al., 1993; Hay et al., 1995; Cunningham et al., 1996). Indeed, PITP function prevents the onset of specific neurodegenerative diseases in Drosophila and mammals, although the in vivo mechanisms of PITP action remain unclear (Hamilton et al., 1997; Milligan et al., 1997). While fungal and metazoan PITPs have been analyzed in some detail, plant PITPs remain uncharacterized. Herein, we report the identification and characterization of two novel soybean Sec14p homologs, designated Ssh1p and Ssh2p. These homologs share some 25% sequence identity with Sec14p, and expression of these proteins is developmentally regulated in the plant. The primary sequence homologies shared by these SSH proteins with Sec14p translate to some level of functional relatedness since high-level expression of either Ssh1p or Ssh2p is sufficient for rescue of the growth and Golgi secretory defects associated with haploid lethal sec14Δ mutations. While Ssh2p exhibits robust PI-transfer activity in vitro, Ssh1p exhibits no such activity. Moreover, neither Ssh1p nor Ssh2p are capable of effecting PC transfer in vitro. In fact, both Ssh1p and Ssh2p are high-affinity phosphoinositide binding proteins that exhibit distinct phospholipid binding specificities. As such, Ssh1p and Ssh2p represent new members of the Sec14p family of proteins that exhibit novel biochemical properties. Finally, we report that Ssh1p is rapidly phosphorylated in response to the exposure of cells to a variety of environmental stresses (e.g. hyperosmotic stress) and that the phosphorylated form of Ssh1p fails to associate with membranes. The distinct biochemical properties of Ssh1p and Ssh2p, when coupled with their differentially regulated patterns of expression in the plant, suggest that Ssh1p and Ssh2p play distinct physiological roles. Ssh1p, in particular, may play a role in regulating the response of soybean plants to environments of high osmolarity. Results Identification of two functional homologs of yeast Sec14p from a higher plant Functional rescue of yeast Sec14p defects represents a simple method for recovering genes encoding heterologous PITPs (Skinner et al., 1993; Tanaka and Hosaka, 1994). To isolate higher plant PITP genes, we constructed a developing soybean seed cDNA library that was engineered for high-level expression in yeast (see Materials and methods). Fifteen cDNA clones, representing two distinct cDNA species designated SSH1 and SSH2, were recovered by virtue of their ability to rescue the growth defects of a sec14-1ts strain at 37°C (Figure 1A). Importantly, plasmid shuffle experiments (see Lopez et al., 1994) demonstrated that SSH1 and SSH2 expression also remedied the unconditional lethality associated with sec14Δ alleles (Figure 1A). Thus, the SSH1 and SSH2 gene products were able to substitute for Sec14p when expressed in yeast. However, this functional substitution required high-level expression of Ssh1p or Ssh2p, as evidenced by our finding that the introduction of centromeric plasmids bearing PPGK::SSH1 or PPGK::SSH2 cassettes was insufficient to support rescue of either sec14Δ or sec14-1ts alleles (e.g. strains CTY1013 and CTY1015; see Table I). Moreover, Ssh2p expression consistently yielded a superior improvement in growth of Sec14p-deficient strains relative to Ssh1p expression (Figure 1A). Figure 1.(A) Expression of soybean SSH1 and SSH2 genes rescues the growth defects of Δsec14 yeast and sec14-1ts strains. Growth properties of a wild-type yeast strain (CTY182), its isogenic sec14-1ts derivative (CTY1-1A), and various sec14 derivative strains carrying either YEp(SSH1) or YEp(SSH2) plasmids are shown. The sec14ts strains (CTY937 and CTY938) all represent strain CTY1-1A carrying the indicated plasmid, while the Δsec14 strains (CTY897 and CTY898) were generated by plasmid shuffle exactly as described by Lopez et al. (1994). These yeast strains were streaked onto YPD plates and incubated for 36 h at the indicated temperatures. High-level expression of either SSH1 or SSH2 not only restored growth of sec14-1ts strains at the normally restrictive temperature at 37°C, but also restored viability at all temperatures to yeast strains carrying the haploid-lethal Δsec14 allele. Thus, when expressed at high levels, Ssh1p and Ssh2p are individually able to fulfill in yeast the essential cellular functions of Sec14p. (B) Efficiency of invertase secretion at 37°C for Δsec14 strains carrying the indicated YEp(SSH) plasmids. The secretion index relates extracellular secreted invertase to total cellular invertase as described (Salama et al., 1990). The secretion indices of wild-type and sec14-1ts strains represent measures of normal secretory proficiency and the magnitude of the sec14-1ts Golgi secretory block, respectively. The Δsec14 strains CTY897 and CTY898 (see Table I) were analyzed for secretory competence to determine the efficiency with which SSH1 and SSH2 expression rescued Δsec14-associated secretory defects, respectively. These data indicate that Ssh1p and Ssh2p expression in yeast significantly alleviated the Golgi secretory defect associated with complete loss of Sec14p function. (C) Ssh1p and Ssh2p share primary sequence homology with fungal PITPs. An alignment of the entire Sec14p, Ssh1p, and Ssh2p primary sequences is shown, and corresponding residue numbers are designated at the far right of each column. These soybean polypeptides each share ∼25% primary sequence identity (and 50% similarity) with Sec14p. Composite identities are indicated by the residues boxed in black, while the Sec14p residues within the white boxes represent amino acid residues conserved in four of the fungal Sec14ps (i.e. Saccharomyces cerevisiae, Kluyveromyces lactis, Yarrowia lipolytica and Schizosaccharomyces pombe) we have characterized to date. Download figure Download PowerPoint Table 1. Yeast strains CTY-1A MATa, ura3-52, Δhis3-200, lys2-801am, sec14-1ts CTY809 MATa, ura3-52, Δhis3-200, lys2-801am, sec14-1ts/YEp lac195 CTY182 MATa, ura3-52, Δhis3-200, lys2-801am CTY807 MATa, ura3-52, Δhis3-200, lys2-801am/YEp lac195 CTY303 MATa, ura3-52, Δhis3-200, cki, sec14ΔP::hisG CTY808 MATa, ura3-52, Δhis3-200, cki, sec14ΔP::hisG/YEp lac195 CTY897 MATa, ade2, ade3, ura3-52, Δhis3-200, leu2, sec14ΔP::hisG/YEp(SSH1, URA3) CTY898 MATa, ade2, ade3, ura3-52, Δhis3-200, leu2, sec14ΔP::hisG/YEp(SSH2, URA3) CTY899 MATa, ura3-52, Δhis3-200, cki, sec14ΔP::hisG/YEp(SSH1) CTY900 MATa, ura3-52, Δhis3-200, cki, sec14ΔP::hisG/YEp(SSH2) CTY920 MATa, ura3-52, Δhis3-200, cki, sec14ΔP::hisG/YEp(SSH1HIS6) CTY937 MATa, ura3-52, Δhis3-200, lys2-801am, sec14-1ts/YEp(SSH1) CTY938 MATa, ura3-52, Δhis3-200, lys2-801am, sec14-1ts/YEp(SSH2) CTY940 MATa, ura3-52, Δhis3-200, cki, sec14ΔP::hisG/YEp(SSH2myc) CTY1013 MATa, ura3-52, Δhis3-200, lys2-801am, sec14-1ts/YCp(PPGK::SSH1) CTY1015 MATa, ura3-52, Δhis3-200, lys2-801am, sec14-1ts/YCp(PPGK::SSH2) SSH1 or SSH2 expression alleviated sec14 growth defects and elicited significant relief of the secretory block associated with Sec14p insufficiencies. As shown in Figure 1B, wild-type strains grown at 37°C exhibited a secretion index (90.9 ± 0.4%) that indicated efficient trafficking of invertase through the secretory pathway to the cell surface. In contrast, an isogenic sec14-1ts strain exhibited a secretion index of only 28.2 ± 2.4%. This value was diagnostic of the accumulation of a major intracellular pool of invertase that is blocked in transit from the yeast Golgi complex (Bankaitis et al., 1989; Franzusoff and Schekman, 1989; Cleves et al., 1991b). However, expression of SSH1 and SSH2 elevated the secretion index of a sec14 null strain grown at 37°C to 55.8 ± 6.2% and 80.2 ± 1.8%, respectively, i.e. values substantially greater than those determined for the sec14-1ts strain at the restrictive temperature (Figure 1B). Again, in accordance with the growth phenotypes described above, Ssh2p expression elicited a reproducibly more efficient rescue of Sec14p-related Golgi secretory defects than did Ssh1p expression. Ssh1p and Ssh2p share primary sequence homology with fungal Sec14ps The nucleotide sequences of the SSH1 and SSH2 cDNAs were determined and found to encode respective open reading frames of 975 and 771 bp, respectively. These sequences have been registered with the DDBJ/EMBL/GenBank database with the following accession numbers: AF024651 (SSH1) and AF024652 (SSH2). SSH1 and SSH2 are inferred to encode proteins of 324 and 256 amino acid residues, respectively, with corresponding molecular masses of 36.9 and 29 kDa. Immunodetection of Ssh1p and Ssh2p, both from producing yeast strains and from soybean sources, provided data in excellent agreement with these expectations (see below). As shown in Figure 1C, Ssh1p and Ssh2p share ∼25% primary sequence identity and 50% similarity with each other, and with Sec14p. The alignments in Figure 1C indicate that the shared primary sequence motifs correspond to motifs that are highly conserved in all characterized fungal Sec14ps, including those from the budding yeast Kluyveromyces lactis (Salama et al., 1990), the dimorphic yeast Yarrowia lipolytica (Lopez et al., 1994), and the fission yeast Schizosaccharomyces pombe (H.B.Skinner and V.A. Bankaitis, unpublished data). In particular, the signature motifs LLRFLRARKF, DGRPVY, YYPERMGKFY and INAP of fungal Sec14ps were all clearly recognizable in the inferred Ssh1p and Ssh2p primary sequences (Figure 1C). No cDNAs from germinating soybean seed that encode proteins exhibiting primary sequence relatedness with mammalian PITPs were obtained in this functional screen. Expression of SSH genes is developmentally regulated in soybean The high frequency of recovery for SSH2 cDNA clones, relative to SSH1 cDNA clones, in our functional screen suggested the possibility that SSH2 was more highly expressed in developing seeds than was SSH1. Northern blot analyses indicated that such was indeed the case. The steady-state abundance of SSH1 transcripts was greatest in leaf and root tissue, and was of only low abundance in developing seeds (Figure 2). In contrast, SSH2 transcripts were most abundant in developing seeds. Only low levels of SSH2 poly(A)+-RNA were detected in leaf tissue and we were unable to detect SSH2 expression in roots (Figure 2). Immunoblotting experiments with the corresponding tissue extracts were entirely consistent with the Ssh1p and Ssh2p expression pattern as deduced from the Northern blot analysis (not shown). Finally, Southern blot analyses, where soybean genomic DNA was individually probed with SSH1 or SSH2 cDNA, revealed a rather simple banding pattern. While the intron/exon organization and pseudogene repertoire for each SSH gene remains undetermined, the banding complexity obtained is consistent with each SSH gene being either unique, or belonging to a small multigene family (Figure 2). Figure 2.Expression of SSH1 and SSH2 is developmentally regulated in the soybean plant. Total genomic DNA from young soybean leaves was isolated as described (Murray and Thompson, 1980). Genomic DNA (10 μg) was restricted with the indicated restriction enzymes, resolved by electrophoresis on 1% agarose gels, and hybridized to radiolabeled SSH1 and SSH2 probes. The restriction enzymes employed do not cleave the corresponding SSH cDNAs. Molecular length markers are presented at the left in kilobase units. Northern (mRNA) blot assays were conducted using 10 μg of poly(A)+ RNA recovered from the specified tissues. The molecular lengths of the hybridizing transcripts were estimated using RNA size standards (not shown). Download figure Download PowerPoint Ssh1p and Ssh2p are not typical PITPs High-level expression of mammalian PITP in yeast is sufficient to rescue the growth and secretory defects associated with sec14-1ts defects (Skinner et al., 1993). The rescue of sec14 defects associated with expression of Ssh1p or Ssh2p in yeast, when coupled with the primary sequence relatedness of Ssh1p and Ssh2p to Sec14p (Figure 1C), suggested that Ssh1p and Ssh2p represented soybean PITPs. As a qualitative test of this possibility, we individually expressed Ssh1p and Ssh2p in the cki, sec14Δ yeast strain CTY303 (Table I) and measured the ability of cytosol prepared from these strains to effect PI and PC transfer in vitro. CTY303 was employed for these studies because it is devoid of endogenous PI- or PC-transfer activity as a consequence of the sec14Δ lesion. This strain retains full viability, in spite of the haploid-lethal nature of sec14Δ, because of the ‘bypass Sec14p’ property of the cki lesion which inactivates choline kinase, the first enzyme of the CDP–choline pathway for PC biosynthesis (Cleves et al., 1991b; Skinner et al., 1993). In these experiments, cytosol represented a clarified salt-stripped fraction of broken cell lysate (see Materials and methods). Salt-stripping was performed because significant fractions of both Ssh1p and Ssh2p were membrane associated (see below). Analysis of the phospholipid transfer properties of Ssh1p and Ssh2p cytosol, prepared from CTY303, yielded unanticipated results, and data are shown in Figure 3A and B. As positive control, the phospholipid transfer activities of wild-type yeast (Sec14p) cytosol were individually measured, and robust PI- and PC- transfer activities were recorded. Both transfer activities were linear in the range of 0 to at least 2 mg added cytosol, and 2 mg wild-type yeast cytosol effected ∼8 and 16% of total input radiolabeled PI- and PC-substrate, respectively, under the employed experimental conditions. Ssh2p cytosol also exhibited robust PI-transfer activity. Indeed, the PI-transfer activity of Ssh2p cytosol was in excess of that measured for Sec14p cytosol, which resulted from Ssh2p expression being driven by a powerful promoter from an expression cassette carried by a multicopy plasmid. Immunoblotting data were consistent with Ssh2p levels in cytosol preparations markedly exceeding those recorded for Sec14p in wild-type yeast cytosol (not shown). Yet, PC-transfer activity was essentially undetectable in Ssh2p cytosol (Figure 3A and B). The demonstration that Ssh2p cytosol effected efficient PI-transfer indicated that our inability to measure PC-transfer was neither the trivial result of inefficient recovery of Ssh2p, nor the result of catastrophic degradation of Ssh2p during cytosol preparation. Characterization of Ssh1p cytosol also provided unanticipated results as it failed to support significant PI- or PC-transfer activity, even at high concentrations (Figure 3A and B). The stability of Ssh1p during the cytosol preparation was not a contributory factor to our inability to record PI- and PC-transfer activity since high levels of full-length Ssh1p were detected by immunoblotting of input cytosol (not shown). Figure 3.Phospholipid transfer activities of cytosol prepared from Ssh1p- and Ssh2p-expressing strains of yeast. A wild-type yeast strain carrying a YEpURA3 plasmid (CTY807), and strains CTY808, Δsec14cki/YEp(URA3); CTY899, Δsec14cki/YEp(PADH::SSH1); and CTY900 Δsec14cki/YEp(PADH::SSH2) were grown in minimal media lacking uracil to mid-logarithmic phase and cells harvested by centrifugation. Cytosol was prepared by adjustment of cell-free extracts to a final concentration of 500 mM KCl and collection of the 100 000 g supernatant fraction (see Materials and methods). The protein concentrations of the resulting cytosolic fractions were determined and the samples were assayed for PI- and PC-transfer activity as described elsewhere (Aitken et al., 1990). PI- and PC-transfer data are shown separately in (A) and (B), respectively. Activity is expressed as the percent of total radiolabeled PI or PC in the assay that was transferred during the course of the experiment after subtraction of background. The background was represented by the transfer values acheived with the PI-/PC-transfer protein deficient cytosol prepared from strain CTY808. Values recorded for the wild-type yeast strain CTY807 (closed circles; designated WT) measure the Sec14p activity normally present in yeast cytosol and serve as positive controls. Values recorded for Ssh1p cytosol (CTY899) and Ssh2p cytosol (CTY900) are represented by stippled squares [YEp(SSH1)] and open circles [YEp(SSH2)], respectively. Data represent the averages of at least three independent experiments. (C) Phospholipid transfer properties of purified Ssh1p and Ssh2p. Recombinant His6-tagged Ssh1p, Ssh2p and Sec14p were purified from E.coli and assayed for PI- and PC-transfer activity as described in the Materials and methods. The efficiency of phospholipid transfer for each Sec14p assay was set at 100% transfer, and the transfer activities of Ssh1p and Ssh2p were compared accordingly. In these assays, recombinant proteins were added at amounts that sustained transfer activity in the linear range with respect to protein concentration, and these amounts are indicated at the bottom. Data represent the averages of at least three independent experiments. Note that >5 μg of Sec14p saturated the PI- and PC-transfer assays, whereas 10-fold greater amounts of recombinant Ssh2p were required to generate comparable PI-transfer activity. Even large amounts of purified recombinant Ssh1p (200 μg) failed to yield measurable PI- or PC-transfer activity. Assay of 200 μg of Ssh2p also failed to generate significant PC-transfer activity. For transfer assays, total input [3H]phosphatidylinositol and [14C]phosphatidycholine equalled ∼7000 and 27 000 c.p.m. per assay, respectively. Background for PI- and PC-transfer assays ranged between 100–198 and 643–800 c.p.m. per transfer reaction, respectively. Download figure Download PowerPoint The yeast cytosol data suggested that neither Ssh1p nor Ssh2p represented typical PITPs, i.e. proteins that exhibit both PI- and PC-transfer activity. To effect a more quantitative comparison of the phospholipid transfer activities of these Sec14p homologs, we expressed His6-tagged Ssh1p and Ssh2p in E.coli. The phospholipid transfer properties of the purified proteins were then determined. As illustrated in Figure 3C, the data obtained with Ssh1p and Ssh2p purified from E.coli broadly recapitulated the results generated with the corresponding yeast cytosol preparations. Ssh1p was inactive with respect to PI- or PC-transfer activity, even when 200 μg of purified protein were assayed. Yet, we believe that the relevant functional properties of Ssh1p are retained in the recombinant protein (see below). Recombinant Ssh2p scored as an active PI-transfer protein (Figure 3C), but was substantially weaker than Sec14p in activity. From titration experiments, we estimate His6-Sec14p purified from E.coli exhibited ∼10-fold greater specific activity for PI-transfer than did His6-Ssh2p recovered from the same source. As expected, in marked contrast to the robust PC-transfer activity elaborated by His6-Sec14p, purified His6-Ssh2p was inactive for PC transfer (Figure 3C), even at 200 μg Ssh2p per PC-transfer assay (not shown). The collective data indicate Ssh1p and Ssh2p exhibit biochemical properties that diverge from those associated with all other presently known PITPs that are characterized by their abilities to effect both PI and PC transfer. Ssh1p is devoid of both PI- and PC-transfer activity, whereas Ssh2p is a novel PI-transfer protein that elaborates PI-transfer activity in the absence of accompanying PC-transfer activity. Ssh1p and Ssh2p are novel phosphoinositide binding proteins We had previously demonstrated that the PI-transfer activity of mammalian PITP was required for expression of this protein to effect a heterologous rescue of Sec14p growth and secretory defects in yeast (Alb et al., 1995). Since mammalian PITP stimulates phosphatidylinositol-4,5-bisphosphate (PIP2) synthesis in permeabilized cells (Cunningham et al., 1995; Hay et al., 1995), we used a photoaffinity radiolabeling strategy to ascertain whether Ssh1p and Ssh2p represented phosphoinositide binding proteins. Specifically, we employed [3H]triester-BZDC-PI(4,5)P2 {[([3H](p-benzoyldihydrocinnamidyl)-amino) propyl]-phosphatidylinositol-4,5-bisphosphate} and [3H]triesterBZDC-InsP3 {[([3H](p-benzoyldihydrocinnamidyl)-amino) propyl]-inositol-1,4,5-trisphosphate} as photo- affinity ligands (Dorman and Prestwich, 1994; Prestwich, 1996; Prestwich et al., 1997, 1998). Both ligands had previously been shown to exhibit highly selective IP3 and PIP2-displaceable photocovalent modification of the pleckstrin homology domain of phospholipase Cδ1 (Tall et al., 1997), and [3H]triester-BZDC photoprobes were successfully employed to characterize the phosphoinositide binding specificity of the mammalian Golgi coatomer complex (Chaudhary et al., 1998). Neither His6-Ssh1p nor His6-Ssh2p were efficiently photolabeled by the PIP2 headgroup photoprobe [3H]BZDC-IP3, even though the control PIP2 binding protein, gelsolin, exhibited intense photolabeling that was competed by excess unlabeled PIP2 (not shown). However, both His6-Ssh1p and His6-Ssh2p were successfully labeled by the [3H]BZDC-PIP2 ligand, and binding of this phosphotriester photoprobe was competed by challenge with excess unlabeled PIP2 (Figure 4A). As expected, the known PIP2 binding protein gelsolin also exh DA - 1998/7/15/ PY - 1998/7/15/ DO - 10.1093/emboj/17.14.4004 VL - 17 IS - 14 SP - 4004-4017 SN - 0261-4189 KW - phosphatidylinositol transfer proteins KW - phosphoinositides KW - signaling KW - soybean KW - stress response ER - TY - JOUR TI - Modeled tunnel currents for high dielectric constant dielectrics AU - Vogel, EM AU - Ahmed, KZ AU - Hornung, B AU - Henson, WK AU - McLarty, PK AU - Lucovsky, G AU - Hauser, , JR AU - Wortman, JJ T2 - IEEE TRANSACTIONS ON ELECTRON DEVICES AB - The effect of dielectric constant and barrier height on the WKB modeled tunnel currents of MOS capacitors with effective oxide thickness of 2.0 nm is described. We first present the WKB numerical model used to determine the tunneling currents. The results of this model indicate that alternative dielectrics with higher dielectric constants show lower tunneling currents than SiO/sub 2/ at expected operating voltages. The results of SiO/sub 2//alternative dielectric stacks indicate currents which are asymmetric with electric field direction. The tunneling current of these stacks at low biases decreases with decreasing SiO/sub 2/ thickness. Furthermore, as the dielectric constant of an insulator increased, the effect of a thin layer of SiO/sub 2/ on the current characteristics of the dielectric stack increases. DA - 1998/6// PY - 1998/6// DO - 10.1109/16.678572 VL - 45 IS - 6 SP - 1350-1355 SN - 0018-9383 ER - TY - JOUR TI - Medium field breakdown origin on metal oxide semiconductor capacitor containing grown-in Czochralski silicon crystal defects AU - Tamatsuka, M AU - Radzimski, Z AU - Rozgonyi, GA AU - Oka, S AU - Kato, M AU - Kitagawara, Y T2 - JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS AB - The medium field breakdown of metal oxide semiconductor capacitor due to the Czochralski silicon crystal originated defect was studied in view of both electrical and structural analyses. By analyzing the local tunneling current which initiates the medium field breakdown, phenomenological defect sizes were calculated from the local tunneling current by assuming the local oxide thinning model. They were the defect diameter as 5 to 50 nm and the local oxide thinning as ∼25 nm. These data were confirmed by direct defect observation using high precision defect isolation procedure followed by transmission electron microscopy. Direct observation revealed that the real defect size was ∼200 nm which correlated well with other recently reported works. The real local oxide thinning,however,was not as large as phenomenological calculation. To explain the differences between phenomenological and real local oxide thinning, the poly-Si grain protrusion induced stress model was proposed. DA - 1998/3// PY - 1998/3// DO - 10.1143/JJAP.37.1236 VL - 37 IS - 3B SP - 1236-1239 SN - 0021-4922 KW - grown-in defect KW - oxide breakdown KW - electron beam induced current KW - vacancy cluster KW - focused ion beam KW - local tunneling current KW - Fowler-Nordheim tunneling current ER - TY - JOUR TI - Interpretation of critical point energy shifts in crystalline Si by near-surface localization of excited electronic states AU - Mantese, L AU - Bell, KA AU - Rossow, U AU - Aspnes, DE T2 - THIN SOLID FILMS AB - Various surface-optical spectra can be described in terms of energy derivatives of the bulk dielectric function. The spectra unequivocally indicate that critical point energies obtained from optical data are not necessarily equal to bulk values and that surface chemical and structural terminations are at least contributing factors. We invoke localization and transition-lifetime arguments to describe these effects. Existing surface-optical calculations do not address these contributions, which may explain in part why discrepancies remain between theory and experiment. DA - 1998/2// PY - 1998/2// DO - 10.1016/S0040-6090(97)00883-3 VL - 313 IS - 1998 Feb. SP - 557-560 SN - 0040-6090 KW - localization KW - wave packet ER - TY - JOUR TI - Interfacial microstructure of Ni/Si-based ohmic contacts to GaN AU - Kaminska, E AU - Piotrowska, A AU - Jasinski, J AU - Kozubowski, J AU - Barcz, A AU - Golaszewska, K AU - Bremser, MD AU - Davis, RF T2 - ACTA PHYSICA POLONICA A AB - Development of low-resistance, thermally stable ohmic contacts is one of the big challenges for the progress in the GaN device technology. We have recently reported on novel Ni/Si-based metallization systems providing ohmic contacts on GaN [1]. We have adopted the idea of Sands et al. [2] of the incorporation of a dopant into the semiconductor subcontact region by solid-phase dissolution and regrowth (SPR). To produce contacts to p-type GaN, Mg dopant is added to the Ni/Si metallization; for n-type GaN, Si is the intended donor dopant [1]. We have shown that these contacts exhibit ohmic behavior after annealing at temperatures ranging from 400 to 600°C, with resistivities of about 1 x 10 -3 Ω cm2 at p-type (p 3 x 10 17 cm-3) and n-type (n 2 x 10 17 cm-3) GaN. The preliminary characterization using Rutherford backscattering spectrometry (RBS), secondary ion mass spectrometry (SIMS), and X-ray diffraction (XRD) indicated that several thermally activated solid-phase processes take place during the formation of ohmic contacts. However, a full understanding of these processes and their influence on the metal/GaN interface properties is still lacking. This study will focus on microstructure of Ni/Si-based contacts. In order to investigate structural properties such aS interface abruptness, phase composition, and defects in the contact region we have applied crosS-sectional tran8mission DA - 1998/9// PY - 1998/9// DO - 10.12693/APhysPolA.94.383 VL - 94 IS - 3 SP - 383-386 SN - 0587-4246 ER - TY - JOUR TI - In situ studies of metal-semiconductor interactions with synchrotron radiation AU - Sayers, DE AU - Goeller, PT AU - Boyanov, BI AU - Nemanich, RJ T2 - JOURNAL OF SYNCHROTRON RADIATION AB - The capabilities and performance of a UHV system for in situ studies of metal–semiconductor interactions are described. The UHV system consists of interconnected deposition and analysis chambers, each of which is capable of maintaining a base pressure of approximately 1 × 10 −10 torr. The deposited materials and their reaction products can be studied in situ with RHEED, XAFS, AES, XPS, UPS and ARUPS. Results from a study of the reaction of 0.7- and 1.7-monolayer-thick films of cobalt with strained silicon–germanium alloys are presented. The signal-to-noise ratio obtained in these experiments indicates that the apparatus is capable of supporting in situ EXAFS studies of ∼0.1-monolayer-thick films. DA - 1998/5/1/ PY - 1998/5/1/ DO - 10.1107/S0909049597015240 VL - 5 SP - 1050-1051 SN - 0909-0495 KW - EXAFS KW - metal-semiconductor contacts KW - silicon-germanium alloys KW - molecular-beam epitaxy ER - TY - JOUR TI - Improvement of wear resistance of pulsed laser deposited diamond-like carbon films through incorporation of metals AU - Wei, Q AU - Narayan, RJ AU - Narayan, J AU - Sankar, J AU - Sharma, AK T2 - MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY AB - We have investigated the characteristics of diamond-like carbon (DLC), DLC doped with Cu, and DLC doped with Ti deposited by a sequential pulsed laser ablation of two targets. The composition of these films was determined by Rutherford backscattering spectrometry and X-ray photoelectron spectroscopy (XPS). Raman spectroscopy and transmission electron microscopy studies showed typical features of DLC with a high fraction of sp3 bonded carbon in the doped films as well as in the undoped films. Wear resistance measurements made on the samples by means of the `crater grinding method' showed that DLC+2.75% Ti has the highest wear resistance, while that of pure DLC has the lowest amongst the samples. Careful analysis of the Raman data indicates a significant shift to shorter wavelength with the addition of metal, which means that the compressive stress in the DLC films has been reduced. We envisaged that the reduction in the compressive stress promotes the wear resistance of the coatings. The XPS studies showed evidence for the formation of Ti–C bonding in the Ti doped sample. Thus metal-doped DLC coatings are expected to improve the tribological properties and enhance the performance of components coated with metal-doped DLC. DA - 1998/5/22/ PY - 1998/5/22/ DO - 10.1016/s0921-5107(98)00150-0 VL - 53 IS - 3 SP - 262-266 SN - 0921-5107 KW - wear resistance KW - pulsed laser deposition KW - diamond-like carbon films KW - metal incorporation ER - TY - PCOMM TI - Growth of gallium phosphide layers by chemical beam epitaxy on oxide patterned (001)silicon substrates AU - Narayanan, V AU - Sukidi, N AU - Hu, CM AU - Dietz, N AU - Bachmann, KJ AU - Mahajan, S AU - Shingubara, S AB - GaP layers grown by chemical beam epitaxy in [110] channels fabricated on oxide-patterned (001)silicon substrates have been examined in cross-section by conventional and high resolution transmission electron microscopy. Results indicate that the layers are single crystalline. For the imaging conditions used, [110] cross-sectional micrographs show that growths in contact with the oxide exhibit twinning on one edge-on variant, whereas faults or twins are observed on two such variants in the layers which nucleate on the silicon substrate. Arguments for rationalizing these observations are developed, and their implications to improve the quality of the layer by confining faults or twins by the oxide sidewall are discussed. DA - 1998/6/26/ PY - 1998/6/26/ DO - 10.1016/s0921-5107(98)00169-x SP - 207-209 KW - gallium phosphide KW - chemical beam epitaxy KW - oxide patterned silicon substrates ER - TY - JOUR TI - Film thickness effects in the Co-Si1-xGex solid phase reaction AU - Boyanov, BI AU - Goeller, PT AU - Sayers, DE AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - The thickness dependence of the reaction of cobalt with epitaxial silicon–germanium alloys (Si1−xGex) has been studied. The reaction products of Co with (100)-oriented Si0.79Ge0.21 after annealing at 800 °C depended on the thickness of the Co film. Complete conversion to CoSi2 occurred only when the thickness of the Co layer exceeded 350 Å. Interface reactions with Co layers thinner than 50 Å resulted in CoSi formation, while a mixture of CoSi and CoSi2 was formed at intermediate thicknesses. X-ray diffraction and extended x-ray absorption fine structure measurements indicated no measurable incorporation of Ge had occurred in either the CoSi or CoSi2. The threshold thickness for nucleation of CoSi2 on (100)-oriented Si1−xGex was determined in the range 0⩽x⩽0.25. The threshold thickness increased superlinearly with the Ge concentration x, and did not depend on the doping of the Si(100) substrate or the strain state of the Si1−xGex film. The observed thickness effect was attributed to preferential Co–Si bonding in the reaction zone and the energy cost of Ge segregation, which accompanies the formation of CoSi and CoSi2 during the reaction of Co with Si1−xGex. DA - 1998/10/15/ PY - 1998/10/15/ DO - 10.1063/1.368872 VL - 84 IS - 8 SP - 4285-4291 SN - 0021-8979 ER - TY - JOUR TI - Co-deposition of cobalt disilicide on silicon-germanium thin films AU - Goeller, PT AU - Boyanov, BI AU - Sayers, DE AU - Nemanich, RJ T2 - THIN SOLID FILMS AB - The formation of CoSi2 on strained epitaxial Si0.8Ge0.2/Si(100) films has been studied as a function of the deposition method and annealing temperature. Two types of deposition processes were used: a direct method, where 5 nm of pure Co metal were deposited at room temperature onto a strained 80 nm thick Si0.8Ge0.2 layer; and a co-deposition method, where 5 nm Co and 18.2 nm Si were simultaneously deposited in a 1:2 ratio onto a strained Si0.8Ge0.2 layer at 450°C. Samples were then annealed at temperatures ranging from 500 to 800°C. Extended X-ray absorbance fine structure spectroscopy (EXAFS) and X-ray diffraction (XRD) were used to characterize the structure of the resulting films. It was found that the samples prepared via the direct deposition method did not convert to CoSi2 at any annealing temperature up to 800°C, while the co-deposited samples formed epitaxial CoSi2 at even the lowest annealing temperature of 500°C. These results are discussed in terms of proposed reaction mechanisms of the different deposition methods, based on consideration of the Co–Si–Ge ternary phase diagram. DA - 1998/5/18/ PY - 1998/5/18/ DO - 10.1016/S0040-6090(97)00941-3 VL - 320 IS - 2 SP - 206-210 SN - 0040-6090 KW - cobalt disilicide KW - silicon-germanium alloys KW - EXAFS ER - TY - JOUR TI - Characterization of zirconium nitride coatings deposited by cathodic arc sputtering AU - Gruss, KA AU - Zheleva, T AU - Davis, RF AU - Watkins, TR T2 - SURFACE & COATINGS TECHNOLOGY AB - Polycrystalline ZrN coatings with a composition of 58.41 at.% Zr and 41.59 at.% N were deposited by cathodic arc evaporation on to Incoloy 825, Hastelloy C22 and Titanium Grade 12 metal substrates. Analyses of the coatings by scanning electron microscopy and Auger electron spectroscopy revealed the presence of 1–8-μm-diameter macroparticles composed of Zr metal. Compressive stresses of 4.06, 3.88 and 2.69 GPa were measured via X-ray diffraction in the coatings deposited on Inc., Hast. and Ti. substrates, respectively. Values for Young's modulus and hardness of 458 and 27.65 GPa, respectively, were obtained via nanoindentation. Studies of the interfacial chemistry via Auger electron spectroscopy and transmission electron microscopy revealed chemically abrupt interfaces and good compositional uniformity throughout the thickness of the zirconium nitride coatings. DA - 1998/9/10/ PY - 1998/9/10/ DO - 10.1016/S0257-8972(98)00584-2 VL - 107 IS - 2-3 SP - 115-124 SN - 0257-8972 KW - cathodic arc sputtering KW - zirconium nitride coatings KW - residual stress KW - incoloy KW - hastelloy KW - microstructure ER - TY - JOUR TI - A unified chemical bonding model for defect generation in a-SiH: Photo-induced defects in photovoltaic devices and current-induced defects in TFTs AU - Yang, H AU - Lucovsky, G T2 - JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS AB - Generation of metastable neutral and charged defects in hydrogenated amorphous silicon (a-Si:H) by reactions involving changes in H-atom bonding arrangements has been studied by ab initio calculations applied to small molecules. A unified defect generation model has been developed in which reactions pathways for photo-induced defect generation in PV devices are initiated by hole-electron pair recombination and/or deep trapping, and in thin film transistor (TFT) devices by electron trapping. Reactions pathways are proposed for intrinsic processes involving only Si and H-atoms, as well as extrinsic processes involving O and NH impurities as well. In photovoltaic (PV) devices, defect generation includes the creation of neutral and charged defects and involves displacive rather than diffusive hydrogen motion, thereby ensuing metastability. The positively charged defects are associated with over-coordinated H-, O- and N-atoms. In TFT devices, defect generation results from electron trapping in anti-bonding orbitals of Si–H groups, and includes the formation of neutral and negatively charged Si-atom dangling bonds. DA - 1998/3// PY - 1998/3// DO - 10.1143/JJAP.37.1082 VL - 37 IS - 3B SP - 1082-1090 SN - 0021-4922 KW - photo-induced defect generation KW - current-induced defect generation KW - PV devices KW - thin film transistors KW - reaction pathways KW - ab initio calculations KW - displacive hydrogen atom motion KW - metastable defects KW - H-bonds ER - TY - JOUR TI - X-ray photoelectron diffraction from (3X3) and (root 3X root 3)R30 degrees (001)(Si) 6H-SiC surfaces AU - King, SW AU - Ronning, C AU - Davis, RF AU - Busby, RS AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - High-resolution (±1°) x-ray photoelectron diffraction (XPD) patterns were obtained along high symmetry azimuths of the (3×3) and (√3×√3)R30° reconstructed (0001)Si 6H–SiC surfaces. The data were compared to XPD patterns obtained from (7×7) Si (111) as well as to models proposed for the (3×3) and (√3×√3)R30° 6H–SiC reconstructions. Forward scattering features similar to those observed from the (7×7) Si (111) were also observed from the (√3×√3)R30° 6H–SiC (0001)Si surface. Additional structures were found and attributed to the substitution of carbon atoms for silicon. Unlike (1×1) and (7×7) Si (111) surfaces, the XPD patterns of (3×3) and (√3×√3)R30° SiC (0001)Si surfaces are different which is due to the presence of an incomplete bilayer of Si on the (3×3) surface. The most significant difference with the Si system is the equivalence of the [101̄0] and [011̄0] azimuths in the (3×3) structure. These results are consistent with a faulted Si bilayer stacking sequence which was proposed based on scanning tunneling microscopy observations. DA - 1998/12/1/ PY - 1998/12/1/ DO - 10.1063/1.368879 VL - 84 IS - 11 SP - 6042-6048 SN - 1089-7550 ER - TY - JOUR TI - Virtual design and analysis of nanometer-scale sensor and device components AU - Brenner, D. W. AU - Schall, J. D. AU - Mewkill, J. P AU - Shenderova, O. A. AU - Sinnott, S. B. T2 - Journal of the British Interplanetary Society DA - 1998/// PY - 1998/// VL - 51 IS - 1998 SP - 137-144 ER - TY - JOUR TI - Transient enhanced diffusion and defect microstructure in high dose, low energy As+ implanted Si AU - Krishnamoorthy, V AU - Moller, K AU - Jones, KS AU - Venables, D AU - Jackson, J AU - Rubin, L T2 - JOURNAL OF APPLIED PHYSICS AB - (001) CZ silicon wafers were implanted with As+ at 100 keV to a dose of 1×1015/cm2 in order to produce a continuous amorphous layer to a depth of about 120 nm. Furthermore, the implant condition was such that the peak arsenic concentration was below the arsenic clustering threshold. Subsequently, a second As+ or Ge+ implant was performed at 30 keV to doses of 2×1015/cm2, 5×1015/cm2 and 1×1016/cm2, respectively, into the as-implanted samples. All of the samples were annealed at 800 °C for 1 h. The second implant was designed to be contained within the amorphous region created by the initial implant. The second As+ implant was also designed to provide the additional arsenic needed to exceed the critical concentration for clustering at the projected range. Of the three samples with the dual As+ implant the clustering threshold was exceeded for the two lower doses while the SiAs precipitation threshold was exceeded at the highest dose. In the case of the dual As+/Ge+ implants the clustering and precipitation thresholds were not reached. Since arsenic and germanium are similar in mass the extent of damage created by these implants would be comparable. The implanted and annealed specimens were analyzed using secondary ion mass spectroscopy and transmission electron microscopy. The difference in the defect evolution and the transient-enhanced diffusion of arsenic beyond the end-of-range region between the As+ and Ge+ implanted and annealed samples was used to isolate the effects of arsenic clustering and precipitation. The results showed that point defects induced during clustering and/or precipitation did not contribute to the enhanced diffusion of arsenic although these defects did coalesce to form extended defects at the projected range. However, damage beyond the end-of-range region did cause enhanced diffusion of arsenic. DA - 1998/12/1/ PY - 1998/12/1/ DO - 10.1063/1.368896 VL - 84 IS - 11 SP - 5997-6002 SN - 1089-7550 ER - TY - JOUR TI - Special issue on interfacial reactions, solid state transformations and thermal management - Foreword AU - Ghosh, G AU - Kang, S AU - Murty, KL AU - Notis, M T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 1998/11// PY - 1998/11// DO - 10.1007/s11664-998-0061-z VL - 27 IS - 11 SP - 1137-1137 SN - 0361-5235 ER - TY - PCOMM TI - Oxidation of a bis[Zn(II) porphyrin] yields a nondisjoint, exchange-coupled pi dication-biradical AU - Shultz, DA AU - Lee, HY AU - Gwaltney, KP AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTOxidation of a Bis[Zn(II) porphyrin] Yields a Nondisjoint, Exchange-Coupled π Dication-BiradicalDavid A. Shultz, Hyoyoung Lee, and Kevin P. GwaltneyView Author Information Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204 Cite this: J. Org. Chem. 1998, 63, 22, 7584–7585Publication Date (Web):October 3, 1998Publication History Received29 July 1998Published online3 October 1998Published inissue 1 October 1998https://doi.org/10.1021/jo981488dCopyright © 1998 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views295Altmetric-Citations16LEARN 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 (99 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Electron paramagnetic resonance spectroscopy,Exchange coupling,Molecules,Oxidation,Pyrroles Get e-Alerts DA - 1998/10/30/ PY - 1998/10/30/ DO - 10.1021/jo981488d SP - 7584-7585 ER - TY - JOUR TI - On the prediction of the shear stress of electrorheological suspensions AU - Wu, CW AU - Conrad, H T2 - JOURNAL OF MATERIALS RESEARCH DA - 1998/11// PY - 1998/11// DO - 10.1557/JMR.1998.0449 VL - 13 IS - 11 SP - 3299-3303 SN - 0884-2914 ER - TY - JOUR TI - Nanoscale scanning force imaging of polarization phenomena in ferroelectric thin films AU - Auciello, O. AU - Gruverman, A. AU - Tokumoto, H. AU - Prakash, S. A. AU - Aggarwal, S. AU - Ramesh, R. T2 - MRS Bulletin DA - 1998/// PY - 1998/// VL - 23 IS - 1 SP - 33-42 ER - TY - JOUR TI - Multiscale modeling approach for calculating grain-boundary energies from first principles AU - Shenderova, OA AU - Brenner, DW AU - Nazarov, AA AU - Romanov, AE AU - Yang, LH T2 - PHYSICAL REVIEW B AB - A multiscale modeling approach is proposed for calculating energies of tilt-grain boundaries in covalent materials from first principles over an entire misorientation range for given tilt axes. The method uses energies from density-functional calculations for a few key structures as input into a disclination structural-units model. This approach is demonstrated by calculating energies of 〈001〉-symmetrical tilt-grain boundaries in diamond. DA - 1998/2/1/ PY - 1998/2/1/ DO - 10.1103/physrevb.57.r3181 VL - 57 IS - 6 SP - R3181-R3184 SN - 1550-235X ER - TY - JOUR TI - Monolayer nitrogen atom incorporation at buried Si-SiO2 interfaces: Preparation by remote plasma oxidation/nitridation and characterization by on-line auger electron spectroscopy AU - Lucovsky, G AU - Niimi, H AU - Koh, K AU - Green, ML T2 - SURFACE REVIEW AND LETTERS AB - This paper presents experimental studies in which N-atoms have been incorporated at Si-SiO 2 interfaces by forming the interface and oxide film by a 300°C remote-plasma-assisted nitridation/oxidation process using N 2 O . Process dynamics have been studied by on-line Auger electron spectroscopy (AES) by interrupted plasma processing. Based on AES studies using N 2 O , O 2 and sequenced N 2 O and O 2 source gases, reaction pathways for (i) N-atom incorporation at and/or (ii) removal from buried Si-SiO 2 interfaces have been identified, and contrasted with reaction pathways for nitridation using conventional furnace processing. DA - 1998/2// PY - 1998/2// DO - 10.1142/S0218625X98000323 VL - 5 IS - 1 SP - 167-173 SN - 0218-625X ER - TY - JOUR TI - Interface electronic transition observed by optical second-harmonic spectroscopy in beta-GaN/GaAs(001) heterostructures AU - Lupke, G AU - Busch, O AU - Meyer, C AU - Kurz, H AU - Brandt, O AU - Yang, H AU - Trampert, A AU - Ploog, KH AU - Lucovsky, G T2 - PHYSICAL REVIEW B AB - Optical second-harmonic spectroscopy was used to probe the interface electronic structure of highly mismatched $\ensuremath{\beta}\ensuremath{-}GaN/GaAs(001)$ heterostructures in the vicinity of the ${E}_{0}$ interband critical point of $\ensuremath{\beta}\ensuremath{-}\mathrm{G}\mathrm{a}\mathrm{N}$. The resonance energy of both bulk and interface two-photon ${E}_{0}$ transitions from layers between 1- and 100-nm thickness are identical, indicating the absence of appreciable amounts of strain and electric fields in this materials system. This finding is in striking contrast to observations made for other materials systems, including ZnSe/GaAs and ${\mathrm{SiO}}_{2}/\mathrm{S}\mathrm{i}$, where large shifts of several 10 meV with respect to the bulk values have been found. DA - 1998/2/15/ PY - 1998/2/15/ DO - 10.1103/physrevb.57.3722 VL - 57 IS - 7 SP - 3722-3725 SN - 1550-235X ER - TY - JOUR TI - Discrete element investigation of stress fluctuation in granular flow at high strain rates AU - Schwarz, OJ AU - Horie, Y AU - Shearer, M T2 - PHYSICAL REVIEW E DA - 1998/2// PY - 1998/2// DO - 10.1103/physreve.57.2053 VL - 57 IS - 2 SP - 2053-2061 SN - 2470-0053 ER - TY - JOUR TI - Wear characteristics of a woodworking knife with a vanadium carbide coating only on the clearance surface (back surface) AU - Kato, C AU - Bailey, JA T2 - ADVANCED CERAMIC TOOLS FOR MACHINING APPLICATION - III DA - 1998/// PY - 1998/// DO - 10.4028/www.scientific.net/kem.138-140.479 VL - 138-1 SP - 479-520 SN - 1013-9826 KW - wood cutting KW - orthogonal cutting KW - up milling KW - vanadium carbide coated tool KW - chromium coated tool KW - self-sharpening ER - TY - JOUR TI - Thermoplastic elastomer gels. I. Effects of composition and processing on morphology and gel behavior AU - Laurer, J. H. AU - Mulling, J. F. AU - Khan, Saad AU - Spontak, Richard AU - Bukovnik, R. T2 - Journal of Polymer Science. Part B, Polymer Physics AB - Thermoplastic elastomer gels (TPEGs) composed of a poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer and a low-volatility, midblock-compatible mineral oil have been investigated at different oil concentrations to ascertain the effect of composition on TPEG morphology and mechanical properties. The impact of thermal processing is also examined by comparing gels thermally quenched to 0°C or slowly cooled to ambient temperature. Transmission electron micrographs reveal that gels with 70 to 90 wt % oil exhibit styrenic micelles measuring ca. 24 nm in diameter. Variation in composition or cooling rate does not have any perceivable effect on micelle size or shape, whereas the rate at which the gels are cooled influences the extent of microstructural order and the time to rupture (tR) at constant strain. Dynamic rheological testing confirms the presence of a physically crosslinked network at TPEG compositions ranging from 70 to 90 wt % oil, independent of cooling rate. Results presented here suggest that the dynamic elastic shear modulus (G′) scales as tαR where α varies from 0.41 to 0.59, depending on cooling rate. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2379–2391, 1998 DA - 1998/// PY - 1998/// DO - 10.1002/(sici)1099-0488(19980930)36:13<2379::aid-polb13>3.3.co;2-7 VL - 36 IS - 13 SP - 2379–2391 ER - TY - JOUR TI - Reflectance difference spectroscopy spectra of clean (3 x 2), (2 x 1), and c(2 x 2) 3C-SiC(001) surfaces: New evidence for surface state contributions to optical anisotropy spectra AU - Rossow, U AU - Lindner, K AU - Lubbe, M AU - Aspnes, DE AU - Zahn, DRT T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - In this study we applied the surface sensitive optical method reflectance difference spectroscopy to investigate the optical response of clean cubic 3C-SiC(001) surfaces. The main reconstructions, the Si-rich (3×2) and (2×1) as well as the C-rich c(2×2) were prepared by annealing in Si flux. For (3×2) we find a strong spectral feature at 4.2 eV that is not observed for the other two reconstructions. Since the direct gap of 3C-SiC is at higher photon energies the 4.2 eV feature must be related to the surface. Angle resolved ultraviolet photoelectron spectroscopy measurements indicate surface states around the X̄ point of the unreconstructed surface Brillouin zone. We conclude that the 4.2 eV feature is associated with this surface state and suggest that it is linked to the E2 gap of bulk Si at 4.2 eV. DA - 1998/// PY - 1998/// DO - 10.1116/1.590174 VL - 16 IS - 4 SP - 2355-2357 SN - 1071-1023 ER - TY - JOUR TI - Photon-induced localization and final-state correlation effects in optically absorbing materials AU - Aspnes, DE AU - Mantese, L AU - Bell, KA AU - Rossow, U T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Two consequences of the absorption of light in optically absorbing materials that appear not to have been recognized previously are: (1) localization of the final electron and hole states involved in the absorption process into wave packets and (2) propagation of these wave packets with their respective group velocities. We demonstrate the existence of these phenomena by applying first-order time-dependent perturbation theory to a simple model that can be solved analytically even when correlations that are ordinarily discarded in the random phase approximation are retained. This approach provides a natural explanation of components in surface- and interface-optical spectra that are related to energy derivatives of the bulk dielectric function εb and apparent differences in nominally bulk critical point energies Eg and broadening parameters Γ depending on surface conditions. DA - 1998/// PY - 1998/// DO - 10.1116/1.590176 VL - 16 IS - 4 SP - 2367-2372 SN - 1071-1023 ER - TY - JOUR TI - Investigation of postoxidation thermal treatments of Si/SiO2 interface in relationship to the kinetics of amorphous Si suboxide decomposition AU - Hinds, B. J. AU - Wang, F. AU - Wolfe, D. M. AU - Hinkle, C. L. AU - Lucovsky, G. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 1998/// PY - 1998/// VL - 16 IS - 4 SP - 2171-2176 ER - TY - JOUR TI - Interface formation and thermal stability of advanced metal gate and ultrathin gate dielectric layers AU - Claflin, B. AU - Lucovsky, G. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 1998/// PY - 1998/// VL - 16 IS - 4 SP - 2154-2158 ER - TY - JOUR TI - Heterointerface dipoles: Applications to (a) Si-SiO2, (b) nitrided Si-N-SiO2, and (c) SiC-SiO2 interfaces AU - Lucovsky, G. AU - Yang, H. AU - Massoud, H. Z. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 1998/// PY - 1998/// VL - 16 IS - 4 SP - 2191-2198 ER - TY - JOUR TI - Electrical properties of (Ba, Sr)TiO3 thin films prepared by liquid delivery MOCVD AU - Lee, W. J. AU - Woolcott, R. R. AU - Basceri, C. AU - Lee, H. Y. AU - Streiffer, S. K. AU - Kingon, A. I. AU - Yang, D. Y. T2 - Journal of the Korean Physical Society DA - 1998/// PY - 1998/// VL - 32 pt.4 IS - suppl. SP - 1652-1656 ER - TY - JOUR TI - Differences between silicon oxycarbide regions at SiC-SiO(2) prepared by plasma-assisted oxidation and thermal oxidations AU - Lucovsky, G AU - Niimi, H AU - Golz, A AU - Kurz, H T2 - APPLIED SURFACE SCIENCE AB - The initial stages of SiCSiO2 interface formation by low temperature (300°C) remote plasma assisted oxidation (RPAO) have been studied by on-line Auger electron spectroscopy (AES) for flat and vicinal 6H SiC(0001) wafers with Si(0001) and C faces (0001), focusing on (i) interfacial bonding and (ii) oxidation rates for thickness up to about 2 nm. DA - 1998/1// PY - 1998/1// DO - 10.1016/S0169-4332(97)00469-8 VL - 123 SP - 435-439 SN - 0169-4332 ER - TY - JOUR TI - Dielectric properties and microstructure of thin BST films AU - Bilodeau, S. M. AU - Carl, R. AU - VanBuskirk, P. C. AU - Roeder, J. F. AU - Basceri, C. AU - Lash, S. E. AU - Parker, C. B. AU - Streiffer, S. K. AU - Kingon, A. I. T2 - Journal of the Korean Physical Society DA - 1998/// PY - 1998/// VL - 32 pt.4 IS - suppl. SP - 1591-1594 ER - TY - JOUR TI - Coupled electron-hole dynamics at the Si/SiO2 interface AU - Wang, W AU - Lupke, G AU - Di Ventra, M AU - Pantelides, ST AU - Gilligan, JM AU - Tolk, NH AU - Kizilyalli, IC AU - Roy, PK AU - Margaritondo, G AU - Lucovsky, G T2 - PHYSICAL REVIEW LETTERS AB - We report a new and surprising enhancement of the electric field at the $\mathrm{Si}/\mathrm{SiO}{}_{2}$ interface following the cessation of intense pulsed near-infrared radiation. The phenomenon, measured by optical second-harmonic generation, occurs only for photon energies and oxide film thickness that exceed respective thresholds. We attribute the new effect to multiphoton hole injection into the oxide and to an asymmetry in electron and hole dynamics, in particular to distinctly different trapping and detrapping processes. DA - 1998/11/9/ PY - 1998/11/9/ DO - 10.1103/PhysRevLett.81.4224 VL - 81 IS - 19 SP - 4224-4227 SN - 0031-9007 ER - TY - JOUR TI - Chemically and geometrically enhanced focused ion beam micromachining AU - Russell, PE AU - Stark, TJ AU - Griffis, DP AU - Phillips, , JR AU - Jarausch, KF T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Improvements in focused ion beam (FIB) material removal rates utilizing geometric and chemical enhancement were investigated. Geometrical optimization of FIB micromachining of Permalloy and diamond was investigated to determine the magnitude of material removal rate gains that could be attained by increasing the angle of the ion beam with respect to the sample surface normal. The combination of geometrical optimization with chemical enhancement (C2Cl4 for Permalloy and H2O and XeF2 for diamond) was then investigated to determine whether additional gains in material removal rate could be attained. FIB sharpening of a diamond nanoindenter tip is also presented as a practical example of diamond micromachining with H2O as the removal rate enhancing species. DA - 1998/// PY - 1998/// DO - 10.1116/1.590197 VL - 16 IS - 4 SP - 2494-2498 SN - 1071-1023 ER - TY - JOUR TI - Cathodoluminescence measurements of suboxide band-tail and Si dangling bond states at ultrathin Si-SiO2 interfaces AU - Young, A. P. AU - Schafer, J. AU - Jessen, G. H. AU - Bandhu, R. AU - Brillson, L. J. AU - Lucovsky, G. AU - Niimi, H. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 1998/// PY - 1998/// VL - 16 IS - 4 SP - 2177-2181 ER - TY - JOUR TI - Surface melting in the heteroepitaxial nucleation of diamond on Ni AU - Yang, PC AU - Liu, W AU - Schlesser, R AU - Wolden, CA AU - Davis, RF AU - Prater, JT AU - Sitar, Z T2 - JOURNAL OF CRYSTAL GROWTH AB - Surface melting associated with the heteroepitaxial nucleation of diamond on Ni was investigated. Scanning electron microscopy of quenched samples revealed flow patterns and a recrystallized surface morphology. A combination of techniques including in situ optical monitoring, differential thermal analysis, Auger depth profile analysis, and cross-section transmission electron microscopy (TEM) analysis were performed to identify the nature of the molten layer. Data obtained from different experiments were in good mutual agreement. All experimental results strongly indicated that a molten Ni–C–H surface layer was involved in the nucleation process. The presence of both carbon and atomic hydrogen played an important role in the depression of the melting point which was measured to be >300°C less than the melting point of pure Ni. DA - 1998/4// PY - 1998/4// DO - 10.1016/S0022-0248(97)00854-3 VL - 187 IS - 1 SP - 81-88 SN - 0022-0248 KW - heteroepitaxial nucleation KW - diamond KW - nickel KW - hydrogen KW - surface melting ER - TY - JOUR TI - Secondary electron imaging as a two-dimensional dopant profiling technique: Review and update AU - Venables, D. AU - Jain, H. AU - Collins, D. C. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 1998/// PY - 1998/// VL - 16 IS - 1 SP - 362-366 ER - TY - JOUR TI - Real-time monitoring of steady-state pulsed chemical beam epitaxy by p-polarized reflectance AU - Bachmann, KJ AU - Sukidi, N AU - Hopfner, C AU - Harris, C AU - Dietz, N AU - Tran, HT AU - Beeler, S AU - Ito, K AU - Banks, HT T2 - JOURNAL OF CRYSTAL GROWTH AB - The structure in the p-polarized reflectance (PR) intensity Rp4(t) - observed under conditions of pulsed chemical beam epitaxy (PCBE) - is modeled on the basis of the four-layer stack: ambient/surface reaction layer (SRL)/epilayer/substrate. Linearization of the PR intensity with regard to the phase factor associated with the SRL results in a good approximation that can be expressed as Rp4 = Rp3 + ΔRp.Rp3 is the reflectivity of the three-layer stack ambient-epilayer-substrate. ΔRp describes the properties of the SRL. An explicit relation is derived between ΔRp(t) and the time-dependent surface concentrations ch(t) (h = 1, 2, …, N) of the constituents of the SRL, which holds for conditions of submonolayer coverage of the surface by source vapor molecules. Under conditions of low temperature PCBE at high flux, the SRL is expected to exhibit nonideal behavior, mandating replacement of the surface concentrations by activities. Also, in this case, the thickness of the SRL must be represented in terms of partial molar volumina Vh. Since the relation between ΔRp(t) and the activities of reactants, intermediates and products of the chemical reactions driving heteroepitaxial growth is non-linear, the extraction of kinetic parameters from the measured time dependence of the PR signal generally requires numerical modeling. DA - 1998/1// PY - 1998/1// DO - 10.1016/s0022-0248(97)00410-7 VL - 183 IS - 3 SP - 323-337 SN - 0022-0248 KW - p-polarized reflectance KW - surface kinetics KW - chemical beam epitaxy KW - real-time process monitoring ER - TY - JOUR TI - Pure and mixed gas acetone/nitrogen permeation properties of polydimethylsiloxane [PDMS] AU - Singh, A AU - Freeman, BD AU - Pinnau, I T2 - JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS AB - The permeability of polydimethylsiloxane [PDMS] to acetone, nitrogen, and acetone/nitrogen mixtures has been determined at 28°C. In pure gas experiments, the permeability of PDMS to nitrogen was 245 × 10−10 cm3(STP) · cm/cm2 · s · cmHg and was independent of pressure. The permeability of PDMS to acetone vapor increased exponentially with increasing acetone pressure. PDMS is much more permeable to acetone than to nitrogen; acetone/nitrogen selectivity increases from 85 to 185 as acetone partial pressure in the feed increases from 0 to 67% of saturation. In mixed gas permeation experiments, the nitrogen permeability coefficient is independent of acetone relative pressure and is equal to the pure gas permeability coefficient. The acetone permeability coefficient has the same value in both mixed gas and pure acetone permeation experiments. Average acetone diffusivity in PDMS, determined as the ratio of permeability to solubility, decreases with increasing acetone concentration due to mild clustering of acetone in the polymer (because acetone is a poor solvent for PDMS) and changes in the polymer–penetrant thermodynamic interactions which influence diffusion coefficients. A Zimm–Lundberg analysis of the acetone sorption isotherm is also consistent with acetone clustering in PDMS. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 289–301, 1998 DA - 1998/1/30/ PY - 1998/1/30/ DO - 10.1002/(SICI)1099-0488(19980130)36:2<289::AID-POLB8>3.0.CO;2-M VL - 36 IS - 2 SP - 289-301 SN - 0887-6266 KW - polydimethylsiloxane KW - permeability KW - sorption KW - mixed gas permeation KW - clustering KW - acetone/nitrogen separation ER - TY - JOUR TI - Phase separation in InGaN grown by metalorganic chemical vapor deposition AU - El-Masry, NA AU - Piner, EL AU - Liu, SX AU - Bedair, SM T2 - APPLIED PHYSICS LETTERS AB - We report on phase separation in thick InGaN films with up to 50% InN grown by metalorganic chemical vapor deposition from 690 to 780 °C. InGaN films with thicknesses of 0.5 μm were analyzed by θ–2θ x-ray diffraction, transmission electron microscopy (TEM), and selected area diffraction (SAD). Single phase InGaN was obtained for the as-grown films with &lt;28% InN. However, for films with higher than 28% InN, the samples showed a spinodally decomposed microstructure as confirmed by TEM and extra spots in SAD patterns that corresponded to multiphase InGaN. DA - 1998/1/5/ PY - 1998/1/5/ DO - 10.1063/1.120639 VL - 72 IS - 1 SP - 40-42 SN - 0003-6951 ER - TY - JOUR TI - Optical approaches for controlling epitaxial growth AU - Aspnes, DE AU - Dietz, N T2 - APPLIED SURFACE SCIENCE AB - Optical spectroscopy of surface and near-surface regions has advanced to the stage where detailed measurements can be made and analyzed in real time. Here, we discuss reported and potential applications of optical probes for sample-driven closed-loop feedback control of semiconductor epitaxy. Parameters that have been controlled include temperature, thickness in both deposition and etching, and composition, including continuously graded compositions. Although considerable progress has been made, much remains to be done before these techniques become viable production tools. DA - 1998/6// PY - 1998/6// DO - 10.1016/s0169-4332(98)00085-3 VL - 130 IS - 1998 June SP - 367-376 SN - 1873-5584 KW - epitaxial growth KW - optical spectroscopy KW - OMCVD ER - TY - JOUR TI - Isolation techniques and electrical characterization of single grain boundaries of Bi2Sr2CaCu2O2 high-temperature superconductor AU - Saleh, AM AU - Schindler, G AU - Sarma, C AU - Haase, DG AU - Koch, CC AU - Kingon, AI T2 - PHYSICA C AB - We have isolated single grain boundaries of a bulk material of polycrystalline high-temperature superconductor Bi2Sr2CaCu2O2 (Bi-2212) tapes. The tapes were grown on a single crystal of MgO or Ag-foil by partial melting of the superconductor. The isolation techniques consisted of fabricating metal micro-contact pads, wire bonding, and laser patterning of the Bi-2212 superconductor. Results of electrical and magnetic measurements of single grain boundaries suggested a possible existence of Josephson-like junctions coexisting with flux flow junctions. In contrast to bulk samples, Tc of a single grain boundary did not change by applying magnetic field. Jc and Tc were found to be greatly dependent on heat treatment and growth conditions. The current–voltage characteristics of a single patterned bridge followed a relation of the form V∼(I−Ic)n for I>Ic with n∼1.2. DA - 1998/2/1/ PY - 1998/2/1/ DO - 10.1016/s0921-4534(97)01762-0 VL - 295 IS - 3-4 SP - 225-234 SN - 0921-4534 ER - TY - JOUR TI - Intrinsic exciton transitions in GaN AU - Shan, W AU - Fischer, AJ AU - Hwang, SJ AU - Little, BD AU - Hauenstein, RJ AU - Xie, XC AU - Song, JJ AU - Kim, SS AU - Goldenberg, B AU - Horning, R AU - Krishnankutty, S AU - Perry, WG AU - Bremser, MD AU - Davis, RF T2 - JOURNAL OF APPLIED PHYSICS AB - Intrinsic excitonic transitions in GaN have been studied using a variety of spectroscopic measurements. Sharp spectral structures associated with intrinsic free excitons could be observed in photoluminescence, reflection, and absorption spectra. The energy positions of excitonic transitions in GaN epitaxial layers were found to be influenced by the residual strain resulting from lattice-parameter and thermal-expansion mismatches between the epilayers and the substrates. The values of the four principal deformation potentials of wurtzite GaN were derived by using the strain tensor components determined by x-ray measurements. The observation of spectral features involving the emission of LO phonons in absorption and photoluminescence excitation spectra at energies above exciton resonances indicate that a phonon-assisted indirect excitation process, which simultaneously generates a free exciton and a LO phonon, is a very significant and efficient process in GaN. The lifetime of the free excitons is found to be longer than the relaxation time of LO-phonon emission but much shorter than that of acoustic-phonon emission. DA - 1998/1/1/ PY - 1998/1/1/ DO - 10.1063/1.366660 VL - 83 IS - 1 SP - 455-461 SN - 0021-8979 ER - TY - JOUR TI - Growth of MoxN films via chemical vapor deposition of MoCl5 and NH3 AU - Roberson, SL AU - Finello, D AU - Davis, RF T2 - SURFACE & COATINGS TECHNOLOGY AB - Polycrystalline MoxN (x = 1 or 2) films have been grown via chemical vapor deposition on 50 μm thick polycrystalline Ti substrates using molybdenum pentachloride (MoCl5) and anhydrous ammonia (NH3) in a cold-wall vertical pancake-style reactor. X-ray diffraction data indicated that a two-phase MoxN assemblage consisting of γ-Mo2N and δ-MoN was present in films deposited above 400 °C. The percentages of γ-Mo2N and δ-MoN in the films decreased and increased, respectively, as the deposition temperature increased at constant NH3flow rates and deposition pressures. The surface macrostructure of the as-deposited films was independent of the deposition temperature and was very similar to that of the uncoated Ti substrate. However, the microstructure of the films varied with the deposition temperature. Energy dispersive X-ray data indicated that films deposited at and above 400 °C did not contain detectable levels of chlorine. DA - 1998/4/21/ PY - 1998/4/21/ DO - 10.1016/S0257-8972(98)00448-4 VL - 102 IS - 3 SP - 256-259 SN - 0257-8972 KW - molybdenum nitride KW - chemical vapour deposition KW - electrodes KW - tribological coatings ER - TY - JOUR TI - Factors affecting two-dimensional dopant profiles obtained by transmission electron microscopy of etched p-n junctions in Si AU - Neogi, SS AU - Venables, D AU - Na, ZY AU - Maher, DM T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Transmission electron microscopy (TEM) was used to characterize image contrast obtained from doping-dependent etching of p-n junctions in silicon. The local variations in crystal thickness give rise to the appearance of thickness fringes which may be interpreted as two-dimensional iso-concentration contours that map the dopant distribution. The samples used for the study consisted of solid source diffusions of boron into substrates of varying resistivities of both n- and p-type. The factors which affect the interpretation of dopant profiles obtained from selective chemical etching of cross section TEM samples is addressed. One-dimensional chemical dopant concentration data were derived from secondary ion mass spectroscopy and one-dimensional carrier concentration data were derived from spreading resistance profiling. DA - 1998/// PY - 1998/// DO - 10.1116/1.589832 VL - 16 IS - 1 SP - 471-475 SN - 1071-1023 ER - TY - JOUR TI - Electrorheology of a zeolite silicone oil suspension with dc and ac fields AU - Wu, CW AU - Chen, Y AU - Conrad, H T2 - JOURNAL OF PHYSICS D-APPLIED PHYSICS AB - The electrorheology of a zeolite/silicone oil suspension with direct current (dc) and alternating current (ac) electric fields was determined at room temperature. The shear yield stress changed only slightly with the field frequency, but the current density increased considerably. Good agreement occurs between the experimental results and those predicted by our model for both the shear yield stress and the current density. This study shows that there is a significant electrorheological (ER) effect over a large frequency range when a suspension has both a high conductivity ratio and a high dielectric ratio of the particles to the host oil. DA - 1998/4/21/ PY - 1998/4/21/ DO - 10.1088/0022-3727/31/8/006 VL - 31 IS - 8 SP - 960-963 SN - 0022-3727 ER - TY - JOUR TI - Electron emission properties of crystalline diamond and III-nitride surfaces AU - Nemanich, RJ AU - Baumann, PK AU - Benjamin, MC AU - Nam, OH AU - Sowers, AT AU - Ward, BL AU - Ade, H AU - Davis, RF T2 - APPLIED SURFACE SCIENCE AB - Wide bandgap semiconductors have the possibility of exhibiting a negative electron affinity (NEA) meaning that electrons in the conduction band are not bound by the surface. The surface conditions are shown to be of critical importance in obtaining a negative electron affinity. UV-photoelectron spectroscopy can be used to distinguish and explore the effect. Surface terminations of molecular adsorbates and metals are shown to induce an NEA on diamond. Furthermore, a NEA has been established for epitaxial AlN and AlGaN on 6H–SiC. Field emission measurements from flat surfaces of p-type diamond and AlN are similar, but it is shown that the mechanisms may be quite different. The measurements support the recent suggestions that field emission from p-type diamond originates from the valence band while for AlN on SiC, the field emission results indicate emission from the AlN conduction band. We also report PEEM (photo-electron emission microscopy) and FEEM (field electron emission microscopy) images of an array of nitride emitters. DA - 1998/6// PY - 1998/6// DO - 10.1016/s0169-4332(98)00140-8 VL - 130 SP - 694-703 SN - 0169-4332 KW - electron emission KW - crystalline diamond KW - III-nitride ER - TY - JOUR TI - Cathodoluminescence studies of the deep level emission bands of AlxGa1-xN films deposited on 6H-SiC(0001) AU - Perry, WG AU - Bremser, MB AU - Davis, RF T2 - JOURNAL OF APPLIED PHYSICS AB - A comprehensive study of the sub band-edge emission bands of AlxGa1−xN (0.06⩽x⩽1) thin films deposited on vicinal and on-axis 6H–SiC(0001) substrates is presented. At 4.2 K strong band-edge emission, ascribed to donor-bound excitons, shallow donor-shallow-acceptor pair emission, and a deep emission band associated with the “yellow” band of GaN, were observed via cathodoluminescence. The energy shift of the shallow donor-shallow-acceptor pair band with respect to the peak of the donor-bound excitons peak exhibited a less than one-to-one correspondence with increasing Al mole fraction due the increasing localization of either the shallow donor and/or shallow acceptor. The yellow band was observed for all compositions and exhibited a similar energy shift with respect to both the donor-bound excitons and the shallow donor-shallow-acceptor pair bands as the Al mole fraction increased, except for a brief decrease at x≈0.5. This decrease was attributed to a donor oxygen level which entered the band gap at approximately this composition. A strong, broad emission band observed at 3.25 eV at 295 K in AlN and commonly associated with oxygen impurities was shown to be closely related to the yellow band of GaN. DA - 1998/1/1/ PY - 1998/1/1/ DO - 10.1063/1.366716 VL - 83 IS - 1 SP - 469-475 SN - 0021-8979 ER - TY - JOUR TI - Anomalous sorption in a poly(styrene-b-isoprene) diblock copolymer near the order-disorder transition AU - Hong, SU AU - Stolken, S AU - Zielinski, JM AU - Smith, SD AU - Duda, JL AU - Spontak, RJ T2 - MACROMOLECULES AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTAnomalous Sorption in a Poly(styrene-b-isoprene) Diblock Copolymer near the Order−Disorder TransitionSeong-Uk Hong, Sylvia Stölken, John M. Zielinski, Steven D. Smith, J. Larry Duda, and Richard J. SpontakView Author Information Departments of Materials Science & Engineering and Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, Institut für Physikalische Chemie, Johannes Gutenberg Universität, 55099 Mainz, Germany, Corporate Research Division, The Procter & Gamble Company, Cincinnati, Ohio 45239, and Departments of Chemical Engineering and Materials Science & Engineering, North Carolina State University, Raleigh, North Carolina 27695 Cite this: Macromolecules 1998, 31, 3, 937–940Publication Date (Web):January 14, 1998Publication History Received28 July 1997Revised13 November 1997Published online14 January 1998Published inissue 1 February 1998https://doi.org/10.1021/ma971127kCopyright © 1998 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views81Altmetric-Citations7LEARN 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. 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Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (54 KB) Get e-AlertsSUBJECTS:Aromatic compounds,Copolymers,Hydrocarbons,Solvents,Sorption Get e-Alerts DA - 1998/2/10/ PY - 1998/2/10/ DO - 10.1021/ma971127k VL - 31 IS - 3 SP - 937-940 SN - 0024-9297 ER - TY - JOUR TI - Aluminum nitride-silicon carbide solid solutions grown by plasma-assisted, gas-source molecular beam epitaxy AU - Kern, RS AU - Rowland, LB AU - Tanaka, S AU - Davis, RF T2 - JOURNAL OF MATERIALS RESEARCH DA - 1998/7// PY - 1998/7// DO - 10.1557/JMR.1998.0257 VL - 13 IS - 7 SP - 1816-1822 SN - 0884-2914 ER - TY - JOUR TI - X-ray microscopy characterization of a thermoplastic / liquid crystalline polymer blend produced by mechanical alloying AU - Smith, Andy AU - Bai, C. AU - Ade, H. AU - Spontak, Richard AU - Balik, C. M. AU - Koch, C. C. T2 - Macromolecular Rapid Communications AB - Incorporation of liquid crystalline polymers (LCPs) into commodity polymers remains a challenge in the design of high-performance, low-cost polymeric blends. Blends of a thermoplastic polymer and a nematic LCP are produced here by mechanical alloying. Functionality sensitive X-ray microscopy reveals LCP dispersions as small as 100 nm in diameter. Intimate mixing remains upon subsequent melt processing, indicating that mechanical alloying is suited for applications such as recycling. DA - 1998/// PY - 1998/// DO - 10.1002/marc.1998.030191104 VL - 19 IS - 1998 SP - 557 ER - TY - JOUR TI - Monolayer incorporation of nitrogen at Si-SiO2 interfaces: Interface characterization and electrical properties AU - Lucovsky, G T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - This article presents a low-temperature plasma-assisted approach for the preparation of Si–SiO2 interfaces with monolayer concentrations of bonded nitrogen atoms (N atoms) at that interface. Localization of N atoms at Si–SiO2 interfaces has been established by on-line Auger electron spectroscopy (AES), off-line secondary ion mass spectrometry, and optical second harmonic generation. On-line AES studies have established that excess suboxide bonding in interfacial transition regions occurs during plasma-assisted oxidation using N2O and O2 source gases, and that a postoxidation rapid thermal anneal at 900 °C for 30 s in an inert ambient reduces the concentration of these suboxide bonding groups. Defect generation at plasma nitrided interfaces in field effect transistor devices is reduced compared to similar devices in which Si–SiO2 interfaces are formed by furnace oxidation in O2. DA - 1998/// PY - 1998/// DO - 10.1116/1.581005 VL - 16 IS - 1 SP - 356-364 SN - 1520-8559 ER - TY - JOUR TI - Mechanisms of field emission from diamond coated Mo emitters AU - Schlesser, R AU - McClure, MT AU - McCarson, BL AU - Sitar, Z T2 - DIAMOND AND RELATED MATERIALS AB - A combination of field emission energy distribution (FEED) and I–V measurements was used to study the field emission mechanisms of tip-shaped molybdenum emitters electrophoretically coated with nominally intrinsic diamond powders. Field-induced band bending was studied as a function of applied voltage and was interpreted in terms of a two-barrier model. Field emitted electrons originated from the conduction band minimum of diamond. Electron injection at the Mo/diamond interface was identified as the dominant field emission current limiting factor. It was concluded that potential negative electron affinity (NEA) properties of diamond did not contribute to a current enhancement. The latter statement was confirmed by the observation that graphite coatings enhanced emission currents in a similar way to diamond coatings. DA - 1998/2// PY - 1998/2// DO - 10.1016/S0925-9635(97)00290-2 VL - 7 IS - 2-5 SP - 636-639 SN - 0925-9635 KW - field emission KW - molybdenum emitters KW - diamond films ER - TY - JOUR TI - Low-temperature (<450 degrees C), plasma-assisted deposition of poly-Si thin films on SiO2 and glass through interface engineering (vol 15, pg 1035, 1997) AU - Wolfe, D. M. AU - Wang, F. AU - Habermehl, S. AU - Lucovsky, G. T2 - Journal of Vacuum Science & Technology. A, Vacuum, Surfaces, and Films DA - 1998/// PY - 1998/// VL - 16 IS - 1 SP - 207 ER - TY - JOUR TI - Intermetallic matrix composites prepared by mechanical alloying - a review AU - Koch, CC T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - This paper reviews research on intermetallic matrix composites synthesized by mechanical alloying. Mechanical alloying, as a powder processing method, results in discontinuous second phases, i.e. dispersoids/discontinuous reinforcements, in the intermetallic matrix. After a discussion of earlier work on dispersoids in intermetallics, intermetallic matrix composites prepared by mechanical alloying will be reviewed for the important structural intermetallics Fe–40 at.% Al, NiAl, Ni3Al, and MoSi2. The unique microstructure and properties of intermetallic matrix dispersoid systems produced by cryomilling will be discussed. The limited studies of nanocrystalline intermetallic matrix composites suggest the possibility of superplastic forming of these materials. DA - 1998/3/31/ PY - 1998/3/31/ DO - 10.1016/s0921-5093(97)00824-1 VL - 244 IS - 1 SP - 39-48 SN - 0921-5093 KW - intermetallic matrix composites KW - mechanical alloying KW - review ER - TY - JOUR TI - Influence of an electric field on the plastic deformation of polycrystalline NaCl at elevated temperatures AU - Yang, D AU - Conrad, H T2 - ACTA MATERIALIA AB - Abstract The effect of a d.c. electric field of 1 kV/cm on the plastic deformation of polycrystalline 99.9% NaCl was determined in compression at 23–532°C (0.28–0.75  T M ) and strain rate e =8.3×10 −4  s −1 . Upon removing the effect of Joule heating it was found that the reduction in the flow stress produced by the field increased with temperature from 0.28 to 0.4  T M , reached a maximum at 0.4  T M and then decreased, becoming nil at 0.75  T M . It is proposed that the reduction in flow stress resulted from an enhancement of cross-slip due to an increase in stacking fault energy. The field had no detectable effect on the plastic deformation kinetics at constant structure in the temperature range 0.28–0.6  T M (cutting of forest dislocations), nor did it appear to have a significant influence on dislocation glide and climb at 0.75  T M . DA - 1998/3/23/ PY - 1998/3/23/ DO - 10.1016/S1359-6454(97)00431-X VL - 46 IS - 6 SP - 1963-1968 SN - 1359-6454 ER - TY - JOUR TI - Impurity gettering to secondary defects created by MeV ion implantation in silicon AU - Brown, RA AU - Kononchuk, O AU - Rozgonyi, GA AU - Koveshnikov, S AU - Knights, AP AU - Simpson, PJ AU - Gonzalez, F T2 - JOURNAL OF APPLIED PHYSICS AB - Impurities in MeV-implanted and annealed silicon may be trapped at interstitial defects near the projected ion range, Rp, and also at vacancy-related defects at approximately Rp/2. We have investigated the temperature dependence of impurity trapping at these secondary defects, which were preformed by annealing at 900 °C. The binding energies of Fe, Ni, and Cu are greater at the vacancy-related defects than at extrinsic dislocation loops. During subsequent processing at temperatures up to 900 °C, the amount of these impurities trapped at Rp/2 increases with decreasing temperature while the amount trapped at Rp decreases, with most of the trapped metals located at Rp/2 in samples processed at temperatures ≲ 700 °C. However, intrinsic oxygen is trapped at both types of defects; this appears to have little effect on the trapping of metallic impurities at extrinsic dislocations, but may inhibit or completely suppress the trapping at vacancy-related defects. DA - 1998/9/1/ PY - 1998/9/1/ DO - 10.1063/1.368438 VL - 84 IS - 5 SP - 2459-2465 SN - 0021-8979 ER - TY - JOUR TI - Hydrogen abstraction kinetics and crystallization in low temperature plasma deposition of silicon AU - Srinivasan, E AU - Parsons, GN T2 - APPLIED PHYSICS LETTERS AB - Exposing a plasma deposited hydrogenated silicon layer to atomic hydrogen results in hydrogen removal from the silicon/hydrogen surface and a net reduction in the total hydrogen content in the layer. For deposition at low temperature, the crystallization fraction corresponds directly with the extent of hydrogen removal. Silicon films deposited using alternating deposition and hydrogen (or deuterium) plasma exposure are characterized by transmission infrared spectroscopy and Raman spectroscopy. Using mass spectroscopy, hydrogen abstraction and etching are observed and identified as important pathways for hydrogen removal at substrate temperatures between 25 °C and 300 °C. Moreover, the hydrogen abstraction kinetics show that the reaction is first order with an activation barrier of −0.4±1 kcal/mol, consistent with a spontaneous Eley–Rideal abstraction process. Energy barrier values are supported by ab initio calculations. DA - 1998/1/26/ PY - 1998/1/26/ DO - 10.1063/1.120785 VL - 72 IS - 4 SP - 456-458 SN - 0003-6951 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000071619600022&KeyUID=WOS:000071619600022 ER - TY - JOUR TI - Growth of highly (0001)-oriented aluminum nitride thin films with smooth surfaces on silicon carbide by gas-source molecular beam epitaxy AU - Jarrendahl, K AU - Smith, SA AU - Zheleva, T AU - Kern, RS AU - Davis, RF T2 - VACUUM AB - Aluminum nitride thin films with very smooth surfaces have been grown by gas-source molecular beam epitaxy on 4H and 6H silicon carbide substrates. High purity ammonia was used as the nitrogen source in conjunction with Al evaporated from an effusion cell. Streaked reflection high energy electron diffraction patterns and reconstructions of the AlN surfaces indicated smooth films. This surface character was confirmed via atomic force microscopy and transmission electron microscopy which showed roughness root mean square values typically below 1 nm and very flat surfaces, respectively. X-ray diffraction showed the films to be highly c-axis oriented and single phase. Major impurities in the AlN films were oxygen and carbon, as revealed by secondary ion mass spectrometry. DA - 1998/3// PY - 1998/3// DO - 10.1016/S0042-207X(97)00177-2 VL - 49 IS - 3 SP - 189-191 SN - 0042-207X ER - TY - JOUR TI - Flat-flame diamond CVD: the effect of pressure and operating conditions for specific applications AU - Wolden, CA AU - Davis, RF AU - Sitar, Z AU - Prater, JT T2 - DIAMOND AND RELATED MATERIALS AB - The radial uniformity and scaleable nature of flat flames make them an attractive technique for diamond deposition The advantages of low-pressure operation relative to atmospheric operation are discussed with respect to reactor design, heat transfer considerations and flame stability. The thermochemistry and kinetics of flat flames are described in regard to process optimization. Examples are provided to describe how to tailor the low-pressure process for the following applications: morphology control for the production of <100> textured films, low-temperature deposition and the introduction of dopants. DA - 1998/2// PY - 1998/2// DO - 10.1016/S0925-9635(97)00206-9 VL - 7 IS - 2-5 SP - 133-138 SN - 0925-9635 KW - boron doping KW - combustion synthesis KW - low temperature KW - texture ER - TY - JOUR TI - Field emission energy distribution analysis of wide-band-gap field emitters AU - Schlesser, R. AU - McCarson, B. L. AU - McClure, M. T. AU - Sitar, Z. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 1998/// PY - 1998/// VL - 16 IS - 2 SP - 689-692 ER - TY - JOUR TI - Electron emission from metal-diamond (100), (111) and (110) interfaces AU - Baumann, PK AU - Nemanich, RJ T2 - DIAMOND AND RELATED MATERIALS AB - Electron emission characteristics of Cu, Co or Zr films on diamond (100), (111) and (110) surfaces were measured by employing ultraviolet photoemission spectroscopy (UPS) and field emission measurements. Prior to metal deposition, the diamond substrates were terminated with oxygen, hydrogen or were free of adsorbates. Deposition of thin Cu or Co films induced a NEA on clean and H-terminated surfaces. A positive electron affinity was observed for Cu or Co on oxygenated surfaces, and depositing thin Zr films resulted in a NEA on all surfaces considered. UPS can be used to correlate the electron affinity and Schottky barrier height. Schottky barriers of metals on clean surfaces were the lowest, whereas they were the highest on oxygen-covered surfaces. Values for the Schottky barrier height ranged from 0.70 eV to 1.60 eV for Cu, 0.35 eV to 1.40 eV for Co and 0.70 eV to 0.95 eV for Zr. A field emission threshold of 79 V μm−1 was measured for oxygenated (100) surfaces. The lowest value of 20 V μm−1 was observed for Zr on the clean (100) surface. For all the metals studied, it was found that a lower Schottky barrier height results in a lower electron affinity, and a lower electron affinity results in a lower field emission threshold. DA - 1998/2// PY - 1998/2// DO - 10.1016/S0925-9635(97)00256-2 VL - 7 IS - 2-5 SP - 612-619 SN - 0925-9635 KW - electron emission KW - metal-diamond interface KW - electron affinity KW - Schottky barrier ER - TY - JOUR TI - Domain patterns in epitaxial rhombohedral ferroelectric films. I. Geometry and experiments AU - Streiffer, SK AU - Parker, CB AU - Romanov, AE AU - Lefevre, MJ AU - Zhao, L AU - Speck, JS AU - Pompe, W AU - Foster, CM AU - Bai, GR T2 - JOURNAL OF APPLIED PHYSICS AB - Possible domain patterns are developed for (001) oriented (pseudocubic indexing) epitaxial rhombohedral perovskite ferroelectric (FR) films. We assume that the films are grown above their Curie temperature (TC) in a cubic paraelectric (PC) state. The rhombohedral distortion consists of a “stretch” along one of the four 〈111〉 crystallographic directions of the cubic perovskite unit cell. Domain pattern formation is concurrent with the PC→FR transformation on cooling from the growth temperature. The domain patterns form to minimize elastic energy in the film, at the energetic expense of both forming domain boundaries and developing local stresses in the substrate. Eight possible domains may form, half of which are related by inversion, thus leading to four mechanically distinct variants. The possible domain walls are determined by mechanical and charge compatibility and follow closely from the analysis of Fousek and Janovec [J. Appl. Phys. 40, 135 (1969)]. Domain patterns may develop with either {100} or {101} boundaries. In both cases, the individual domains in the patterns are energetically degenerate and thus equal width lamellar patterns are predicted. When polarization is included in the analysis, the {100} boundary patterns have no normal component of the net polarization, whereas the {101} boundary patterns correspond to the fully poled state. We report on experimental observation of {100} domain patterns in epitaxial PbZr0.80Ti0.20O3 and PbZr0.65Ti0.35O3 films. DA - 1998/3/1/ PY - 1998/3/1/ DO - 10.1063/1.366632 VL - 83 IS - 5 SP - 2742-2753 SN - 0021-8979 ER - TY - JOUR TI - Domain pattern formation in epitaxial rhombohedral ferroelectric films. II. Interfacial defects and energetics AU - Romanov, AE AU - Lefevre, MJ AU - Speck, JS AU - Pompe, W AU - Streiffer, SK AU - Foster, CM T2 - JOURNAL OF APPLIED PHYSICS AB - The coherency defect technique is developed for the domain pattern energetics in rhombohedral (001) epitaxial ferroelectric films. The coherency defects that are necessary to maintain the epitaxy during the ferroelectric phase transition are considered to be the only sources of elastic strains and stresses (and, correspondingly energy) in the film/substrate system. The coherency defects include: (i) a uniform distribution of edge dislocations which are responsible for the in-plane tension or compression and have Burgers vectors parallel to the interface; and two kinds of mesoscale defects: (ii) Somigliana screw dislocations which are responsible for in-plane shear; and (iii) wedge disclinations which are responsible for the out of plane rotations in neighboring domains. Using this approach, analytical expressions were found for the elastic energy in the film/substrate system for both the {101}-ri/rj and the {100}-ri/rj domain patterns. These two configurations differ by the orientation of domain walls, coherency defect content, and also the morphology of the free surface (flat versus puckered surfaces). Calculations are performed for screened mesoscale coherency defect configurations that represent a single embedded domain pattern and multidomain patterns. The following mesoscale defect configurations are used for these calculations: Somigliana dislocation dipoles, wedge disclination dipoles, Somigliana dislocation quadrupoles, and disclination quadrupoles. It is predicted that there is no critical thickness for domain pattern formation in rhombohedral ferroelectric epitaxial films. Agreement is shown between experimentally observed domain widths and theoretically predicted values. DA - 1998/3/1/ PY - 1998/3/1/ DO - 10.1063/1.366636 VL - 83 IS - 5 SP - 2754-2765 SN - 0021-8979 ER - TY - JOUR TI - Defects and interfaces in epitaxial ZnO/alpha-Al2O3 and AlN/ZnO/alpha-Al2O3, heterostructures AU - Narayan, J AU - Dovidenko, K AU - Sharma, AK AU - Oktyabrsky, S T2 - JOURNAL OF APPLIED PHYSICS AB - We have investigated the nature of epitaxy, defects (dislocations, stacking faults, and inversion domains), and heterointerfaces in zinc oxide films grown on (0001) sapphire and explored the possibility of using it as a buffer layer for growing group III nitrides. High quality epitaxial ZnO films were grown on sapphire using pulsed laser deposition in the temperature range 750–800 °C. The epitaxial relationship of the film with respect to (0001) sapphire was found to be (0001)ZnO∥(0001)sap, with in-plane orientation relationship of [011̄0]ZnO∥[1̄21̄0]sap. This in-plane orientation relationship corresponds to a 30° rotation of ZnO basal planes with respect to the sapphire substrate, which is similar to the epitaxial growth characteristics of AlN and GaN on sapphire. The threading dislocations in ZnO were found to have mostly 1/3〈112̄0〉 Burgers vectors. The planar defects (mostly I1 stacking faults) were found to lie in the basal plane with density of about 105 cm−1. We have grown epitaxial AlN films at temperatures around 770 °C using ZnO/sapphire heterostructure as a substrate and observed the formation of a thin reacted layer at the AlN/ZnO interface. The implications of low defect content in ZnO films compared to III–V nitrides and the role of ZnO films as a buffer layer for III–V nitrides are discussed. DA - 1998/9/1/ PY - 1998/9/1/ DO - 10.1063/1.368440 VL - 84 IS - 5 SP - 2597-2601 SN - 0021-8979 ER - TY - JOUR TI - A positron annihilation study of the evolution of amorphization in Nb3Sn by mechanical milling AU - Nasu, T. AU - Cho, Y. S. AU - Naslund, R. A. AU - Jones, P. L. AU - Greer, A. L. T2 - Journal of Non-crystalline Solids DA - 1998/// PY - 1998/// VL - 234 IS - 1998 July SP - 594-599 ER - TY - JOUR TI - Reaction kinetics of silicon carbide deposition by gas-source molecular-beam epitaxy AU - Kern, R. S. AU - Tanaka, S. AU - Rowland, L. B. AU - Davis, R. F. T2 - Journal of Crystal Growth DA - 1998/// PY - 1998/// VL - 183 IS - 4 SP - 581-593 ER - TY - JOUR TI - Miscibilization of reactive polymers during early-stage spinodal decomposition AU - Yashin, , VV AU - Spontak, RJ T2 - AICHE JOURNAL AB - Abstract Reactive compatibilization constitutes an important method by which to control the size scale of phase separation in immiscible polymer blends. If a polymer pair exhibits a miscibility window at experimentally accessible temperatures, then reactive chain coupling can also be used to enhance the miscibility of the blend during spinodal decomposition in the biphasic region. We consider here the simultaneous phase separation and chemical reaction of A and B homopolymer blends in which end‐functionalized A chains react with a variety of functionalized B chains to form either AB diblock, ABA triblock, or n ‐armed B‐g‐A graft copolymers. Analytical expressions for the structure factors and Onsager kinetic coefficients are developed for each of these copolymer architectures in the kinetically controlled mean‐field limit of early‐stage spinodal decomposition. Multifunctional conversion‐architecture‐phase stability (CAPS) diagrams are introduced to facilitate comparison of the effect of copolymer architecture on reaction‐driven blend miscibilization. DA - 1998/2// PY - 1998/2// DO - 10.1002/aic.690440218 VL - 44 IS - 2 SP - 416-426 SN - 1547-5905 ER - TY - JOUR TI - Indentation-Energy-to-Fracture (IEF) parameter for characterization of DBTT in carbon steels using nondestructive Automated Ball Indentation (ABI) technique AU - Haggag, F. M. AU - Byun, T. S. AU - Hong, J. H. AU - Miraglia, P. Q. AU - Murty, K. L. T2 - Scripta Materialia DA - 1998/// PY - 1998/// VL - 38 IS - 4 SP - 645-651 ER - TY - JOUR TI - In-situ nuclear magnetic resonance investigation of strain, temperature, and strain-rate variations of deformation-induced vacancy concentration in aluminum AU - Murty, KL AU - Detemple, K AU - Kanert, O AU - Dehosson, JTM T2 - METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE AB - Critical strain to serrated flow in solid solution alloys exhibiting dynamic strain aging (DSA) or Portevin-LeChatelier effect is due to the strain-induced vacancy production. Nuclear magnetic resonance (NMR) techniques can be used to monitor in situ the dynamical behavior of point and line defects in materials during deformation, and these techniques are nondestructive and noninvasive. The new CUT-sequence pulse method allowed an accurate evaluation of the strain-enhanced vacancy diffusion and, thus, the excess vacancy concentration during deformation as a function of strain, strain rate, and temperature. Due to skin effect problems in metals at high frequencies, thin foils of Al were used and experimental results correlated with models based on vacancy production through mechanical work (vs thermal jogs), while in situ annealing of excess vacancies is noted at high temperatures. These correlations made it feasible to obtain explicit dependencies of the strain-induced vacancy concentration on test variables such as the strain, strain rate, and temperature. These studies clearly reveal the power and utility of these NMR techniques in the determination of deformation-induced vacancies in situ in a noninvasive fashion. DA - 1998/1// PY - 1998/1// DO - 10.1007/s11661-998-0168-0 VL - 29 IS - 1 SP - 153-159 SN - 1543-1940 ER - TY - JOUR TI - Ultrathin silicon oxynitride films grown by Ar/N2O remote plasma processing AU - Smith, BC AU - Lamb, HH T2 - JOURNAL OF APPLIED PHYSICS AB - On-line Auger electron spectroscopy, secondary ion mass spectroscopy, and angle-resolved x-ray photoelectron spectroscopy (ARXPS) were employed to determine the concentration, spatial distribution, and local chemical bonding of nitrogen in ultrathin oxynitride films grown by Ar/N2O remote plasma processing. Nitrogen incorporation in the films occurs primarily at the Si–SiO2 interface irrespective of rf power (5–50 W); however, the interfacial nitrogen concentration increases with rf power. Up to 0.6 monolayers of nitrogen atoms, bonded as (Si–)3N, are incorporated at the interface. Atomic oxygen generated in N2O plasma decomposition scavenges nitrogen from the bulk of the film, effectively confining nitrogen to a very narrow region near the substrate. A very small concentration of nitrogen, bonded as (Si–)2N–O, is detected on the top surface of the film by ARXPS. DA - 1998/6/15/ PY - 1998/6/15/ DO - 10.1063/1.367881 VL - 83 IS - 12 SP - 7635-7639 SN - 0021-8979 ER - TY - JOUR TI - Surface modification of nitrile rubber by plasma polymerization AU - Ratway, R. J. AU - Balik, C. M. T2 - Plasmas and Polymers DA - 1998/// PY - 1998/// DO - 10.1023/b:papo.0000005943.19927.a8 VL - 3 IS - 2 SP - 129 ER - TY - JOUR TI - Properties and design of electrorheological suspensions AU - Conrad, H T2 - MRS BULLETIN DA - 1998/8// PY - 1998/8// DO - 10.1557/S0883769400030803 VL - 23 IS - 8 SP - 35-42 SN - 0883-7694 ER - TY - JOUR TI - Optical activation of Be implanted into GaN AU - Ronning, C AU - Carlson, EP AU - Thomson, DB AU - Davis, RF T2 - APPLIED PHYSICS LETTERS AB - Single crystalline (0001) gallium nitride layers were implanted with beryllium. Photoluminescence (PL) measurements were subsequently performed as a function of implantation dose and annealing temperature. One new line in the PL spectra at 3.35 eV provided strong evidence for the presence of optically active Be acceptors and has been assigned to band–acceptor (eA) recombinations. The determined ionization energy of 150±10 meV confirmed that isolated Be has the most shallow acceptor level in GaN. Co-implantation of nitrogen did not enhance the activation of the Be acceptors. DA - 1998/9/21/ PY - 1998/9/21/ DO - 10.1063/1.122225 VL - 73 IS - 12 SP - 1622-1624 SN - 0003-6951 ER - TY - JOUR TI - Lineshapes of surface induced optical anisotropy spectra measured by RDS/RAS AU - Rossow, U AU - Mantese, L AU - Aspnes, DE T2 - APPLIED SURFACE SCIENCE AB - In this paper we discuss lineshapes of reflectance-difference spectroscopy (RDS/RAS) spectra of various surfaces. This work aims toward a basic understanding of the surface optical response. We find that in some cases RDS spectra are given by the bulk dielectric function or its energy derivative. In the former case screening effects such as the surface local field effect are dominant. In the latter case the surface modifies the bulk electronic structures and we find that the excited states must be localized near the surface. Even in the simplest case where the anisotropy originates at the surface the optical anisotropy in general depends on the dielectric function of the bulk as well as that of the surface. DA - 1998/1// PY - 1998/1// DO - 10.1016/S0169-4332(97)00544-8 VL - 123 IS - 1998 Jan. SP - 237-242 SN - 0169-4332 ER - TY - JOUR TI - Discrete meso-dynamic simulation of thermal explosion in shear bands AU - Tamura, S AU - Horie, Y T2 - JOURNAL OF APPLIED PHYSICS AB - A two-dimensional discrete element code (DM2), was used to model a complex interplay of deformation and chemical reaction in a region of localized shear at the particle level. Two exothermic mixtures of Nb–Si and Ni–Al particles having dimensions of 5 μm×25 μm were considered. Computational experiments showed that the mixtures exhibit a classical phenomenon of thermal explosion under high rates of shearing. The threshold shear rates were found to be approximately 1.2×108/s and 8.0×107/s for the Nb–Si and Ni–Al mixtures, respectively. The ignition conditions were sensitive to the thermal boundary conditions and the computationally observed values are considered to be the upper limits. The thermal explosion results from the interaction of mechanical mass mixing and heating that were primarily caused by thinning (plastic deformation) and fragmentation. The modeling showed an interesting result: that there is a ratio of fracture strengths that maximizes the mass mixing. DA - 1998/10/1/ PY - 1998/10/1/ DO - 10.1063/1.368532 VL - 84 IS - 7 SP - 3574-3580 SN - 0021-8979 ER - TY - JOUR TI - Study of the epitaxial-lateral-overgrowth (ELO) process for GaN on sapphire AU - Yu, ZH AU - Johnson, MAL AU - Brown, JD AU - El-Masry, NA AU - Cook, JW AU - Schetzina, JF T2 - JOURNAL OF CRYSTAL GROWTH AB - Growth of GaN by MOVPE on mismatched substrates such as sapphire and SiC produces a columnar material consisting of many hexagonal grains ∼0.2–1.0 μm in diameter. However, the epitaxial–lateral-overgrowth (ELO) process for GaN creates a new material – single-crystal GaN. We have studied the ELO process using a MOVPE reactor featuring vertical gas flows and fast substrate rotation to synthesize GaN ELO samples. Characterization experiments consisted of plan-view scanning electron microscopy and vertical-cross-section transmission electron microscopy studies, which disclosed a large reduction in dislocations in the ELO regions of the GaN samples. Panchromatic and monochromatic cathodoluminescence images and spectra were employed to study the spatial variation of the optical properties of the GaN ELO samples. DA - 1998/12// PY - 1998/12// DO - 10.1016/S0022-0248(98)00638-1 VL - 195 IS - 1-4 SP - 333-339 SN - 0022-0248 KW - gallium nitride KW - MOVPE KW - epitaxial lateral overgrowth ER - TY - JOUR TI - Some effects of an electric field on the plastic deformation of metals and ceramics AU - Conrad, H T2 - MATERIALS RESEARCH INNOVATIONS AB - The external parameters generally considered in the plastic deformation of metals and ceramics are the temperature, pressure or stress and time. Usually neglected are the effects of electric and magnetic fields. However, such fields can often have a significant influence, especially when applied concurrently with the more common parameters. Some examples of the effects of an electric field on the plastic deformation of metals and ceramics found by the author and his coworkers are presented. Included are the following: (a) the influence of electropulsing on the flow stress of metals at 78–300 K, (b) the effect of an external electric field (surface charge) on the superplastic deformation of the 74754 Al alloy, (c) the influence of an electric field on the flow stress and ductility of polycrystalline NaCl at 0.28–0.75 TM and (d) the effect of an electric field on the super-plastic deformation of 3Y-TZP. Mechanisms responsible for the observed effects are considered. DA - 1998/5// PY - 1998/5// DO - 10.1007/s100190050053 VL - 2 IS - 1 SP - 1-8 SN - 1432-8917 KW - electric field KW - current density KW - electroplasticity KW - electron wind KW - vacancies KW - cross slip KW - space charge KW - superplasticity KW - flow stress ER - TY - JOUR TI - Optical and structural properties of lateral epitaxial overgrown GaN layers AU - Freitas, J. A. AU - Nam, O. H. AU - Zheleva, T. S. AU - Davis, R. F. T2 - Journal of Crystal Growth DA - 1998/// PY - 1998/// VL - 190 IS - 1998 June SP - 92-96 ER - TY - JOUR TI - Nucleation and growth of Pd clusters in mordenite AU - Reifsnyder, SN AU - Otten, MM AU - Lamb, HH T2 - CATALYSIS TODAY AB - The nucleation and growth of Pd clusters in mordenite were investigated using in situ extended X-ray absorption fine structure (EXAFS) spectroscopy and Fourier transform infrared (FTIR) spectroscopy of adsorbed CO. Calcination of [Pd(NH3)4]2+-exchanged mordenite at 350°C in O2 results in decomposition of the amine complex and formation of square-planar Pd2+ oxo species within the mordenite pores. Reduction of these species at 150°C in H2 yields Pd clusters with an average nuclearity of 3. On an average two 2.22 Å Pd–O bonds are associated with each Pd3 cluster; we infer that this interaction serves to anchor the clusters within the pores. After reduction at 150°C, the FTIR spectrum of irreversibly adsorbed CO is indicative of a mixture of Pd+, Pdδ+, and Pd0 carbonyl species. Reduction at 350°C produces larger intrazeolitic Pd clusters (average nuclearity of 6) that exhibit only a weak interaction with the mordenite, as evidenced by their facile aggregation in the presence of CO at 30°C. Reduction at 450°C yields large 20 Å Pd clusters that we infer are located on external mordenite surfaces or locally disrupt the intracrystalline structure. DA - 1998/3/2/ PY - 1998/3/2/ DO - 10.1016/S0920-5861(97)00121-1 VL - 39 IS - 4 SP - 317-328 SN - 0920-5861 KW - palladium catalysts KW - metal clusters KW - mordenite KW - metal-support interaction KW - EXAFS spectroscopy ER - TY - JOUR TI - Mechanical properties of nanotubule fibers and composites determined from theoretical calculations and simulations AU - Sinnott, SB AU - Shenderova, OA AU - White, CT AU - Brenner, DW T2 - CARBON AB - Theoretical Young's moduli have been estimated for carbon fibers composed of single-walled fullerene nanotubules aligned in the direction of the tubule axis. In the limit of infinitely long tubules, the fibers can have a Young's modulus comparable to that of diamond. Exploiting this property of nanotubule fibers, we investigate a new carbon composite composed of layered nanotubule fibers and diamond. Such a composite is found to be a high-modulus, low-density material that is quite stable to shear and other distortions. DA - 1998/// PY - 1998/// DO - 10.1016/s0008-6223(97)00144-9 VL - 36 IS - 1-2 SP - 1-9 SN - 0008-6223 KW - nanotubes KW - carbon composites KW - diamond KW - molecular simulation KW - mechanical properties ER - TY - JOUR TI - Lateral epitaxial overgrowth of GaN films on SiO2 areas via metalorganic vapor phase epitaxy AU - Nam, OH AU - Zheleva, TS AU - Bremser, MD AU - Davis, RF T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 1998/4// PY - 1998/4// DO - 10.1007/s11664-998-0393-8 VL - 27 IS - 4 SP - 233-237 SN - 0361-5235 KW - coalescence KW - gallium nitride (GaN) KW - lateral epitaxial overgrowth KW - metalorganic vapor phase epitaxy (MOVPE) KW - selective growth ER - TY - JOUR TI - Interfacial sub-oxide regions at Si-SiO2 interfaces: minimization by post-oxidation rapid thermal anneal AU - Lucovsky, G AU - Koh, K AU - Chaflin, B AU - Hinds, B T2 - APPLIED SURFACE SCIENCE AB - Transition regions at SiSiO2 interfaces contain su☐ide bonding arrangements which contribute to interface roughness and may give rise to electronically active defects. Interfacial transition regions with su☐ide bonding are a direct result of thermal and plasma-assisted oxidation at temperatures up to at least 800°C, but sub-oxide bonding is significantly reduced following a 30 s, 900°C RTA. The kinetics of annealing are essentially the same as those for separation of homogeneous sub-oxide thin films (SiOx, x < 2) into silicon nanocrystals and stoichiometric SiO2. DA - 1998/1// PY - 1998/1// DO - 10.1016/S0169-4332(97)00528-X VL - 123 SP - 490-495 SN - 1873-5584 ER - TY - JOUR TI - Influence of mixed particle size on electrorheological response AU - Wu, CW AU - Conrad, H T2 - JOURNAL OF APPLIED PHYSICS AB - Two sizes (6 and 100 μm average diameter) glass spheres suspended in silicone oil (volume fraction φ=0.3) were used to investigate the influence of particle size on electrorheological response at a shear rate 2 s−1. The larger particles gave a higher shear yield stress but a lower current density at zero shear than the smaller ones. When the two particle sizes were mixed together, the shear yield stress decreased, reaching a minimum when the volume fraction of the small particles equals that of the large particles. The minimum in the current density occurred when the ratio of the volume of small to large particles was ∼1/3. DA - 1998/4/1/ PY - 1998/4/1/ DO - 10.1063/1.366621 VL - 83 IS - 7 SP - 3880-3884 SN - 0021-8979 ER - TY - JOUR TI - Heteroepitaxial nucleation of diamond on nickel AU - Sitar, Z AU - Liu, W AU - Yang, PC AU - Wolden, CA AU - Schlesser, R AU - Prater, JT T2 - DIAMOND AND RELATED MATERIALS AB - Highly oriented diamond has been grown on (100) nickel substrates by the hot filament chemical vapor deposition method. Epitaxial nuclei were obtained by a diamond powder seeding and high temperature annealing process. Since the timing of the process was crucial for the achievement of a high degree of orientation and high density of diamond nuclei, a real-time, in-situ laser reflectometry system was developed to monitor changes in surface morphology observed during the high temperature annealing stage. Characteristic features observed in the intensities of reflected and scattered light were interpreted by comparison with scanning electron micrographs of the samples quenched at sequential stages of the process. It was concluded that the scattered light signal can be effectively used as a process steering parameter. Using this technique, oriented nucleation and growth of diamond on Ni was reproducibly achieved. Auger spectroscopy showed that up to 6 at% of carbon was dissolved in the nickel surface layer. The investigation of interfacial microstructures and phases involved by transmission electron microscopy revealed the formation of Ni4C already in the early stages of nucleation. This phase was manifested as coherent precipitates and is believed to have been the precursor for diamond nucleation. Perfectly epitaxial diamond was grown by this process. The epitaxial relationship was determined by cross-sectional transmission electron microscopy and selected area diffraction analysis. DA - 1998/2// PY - 1998/2// DO - 10.1016/S0925-9635(97)00244-6 VL - 7 IS - 2-5 SP - 276-282 SN - 0925-9635 KW - heteroepitaxy KW - heated filament KW - nickel KW - diamond ER - TY - JOUR TI - Grain size dependence of electroplastic effect in NaCl AU - Yang, D. AU - Conrad, H. T2 - British Ceramic Transactions DA - 1998/// PY - 1998/// VL - 97 IS - 6 SP - 263-267 ER - TY - JOUR TI - Directional copper deposition using dc magnetron self-sputtering AU - Radzimski, Z. J. AU - Posadowski, W. M. AU - Rossnagel, S. M. AU - Shingubara, S. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 1998/// PY - 1998/// VL - 16 IS - 3 SP - 1102-1106 ER -