bluuebunny/crossref_metadata_2025_split huggingface dataset:
ECR Plasma Synthesis of Silicon Nitride Films ON GaAs and InSb
Authors: Barbour J. C. , Lovejoy M. L. , Ashby C. I. H. , Howard A. J. , Custer J. S. , Shul R. J. 
Published: March 2011

ABSTRACTThe growth of high-quality dielectric films from Electron Cyclotron Resonance (ECR) plasmas provides for low-temperature surface passivation of compound semiconductors. Silicon nitride (SiNx) films were grown at temperatures from 30°C to 250°C on GaAs substrates. The stress in the films was measured as a function of bias applied during growth (varied from 0 to 200 V), and as a function of sample annealing treatments. Composition profiles of the samples were measured using ion beam analysis. The GaAs photoluminescence (PL) signal after SiNx growth without an applied bias (ion energy = 30 eV) was twice as large as the PL signal from the cleaned GaAs substrate. The PL signal from samples biased at -50 and -100 V indicated that damage degraded the passivation quality, while atomic force microscopy of these samples showed a three fold increase in rms surface roughness relative to unbiased samples. The sample grown with a bias of-200 V showed the largest reduction in film stress but also the smallest PL signal.
Microstructure and Residual Stresses in Al2O3 Prepared by Ion Beam Assisted Deposition
Authors: Goldiner M. G. , Was G. S. , Parfitt L. J. , Jones J. W. 
Published: March 2011

ABSTRACTAlumina films synthesized by ion beam assisted deposition (EBAD) were characterized in terms of their microstructure and residual stress. Normalized energy per deposited atom, En, ranged from 0 to 130 eV/atom. The microstructure of PVD films (En=0) is a mixture of crystalline (γ-Al2O3) and amorphous phases and IBAD films are amorphous. Density and stoichiometry vary between 2.6 and 3.1 g/cm3 and 1.3 and 1.6, respectively. Neither are dependent on either ion-to-atom arrival rate ratio, R, or En. The film porosity is in the form of small (4-6 nm) voids of density 1017 - 1018 cm-3. Bombarding gas is incorporated with 80% efficiency to levels of 4-5 at. %. A tensile residual stress of 0.3 GPa exists in PVD films. A rapid transition to high compressive stresses occurs with increased En, with a saturation of -0.4 GPa occurring at high En There is a strong correlation between gas incorporation and residual film stress. However, no existing models are capable of providing a quantitative explanation of the results.
Ion Beam-Assisted Deposition of Biaxially Aligned CeO2 and ZrO2 Thin Films on Amorphous Substrates
Authors: Ressler Kevin G. , Sonnenberg Neville , Cima Michael J. 
Published: March 2011

ABSTRACTDeposition of HTSC and other films is often restricted to lattice-matched single crystal substrates to produce desired epitaxial films. Ion assisted, electron beam deposition (IBAD) has been used to evaporate biaxially aligned ceria and zirconia films on amorphous substrates, thus producing a surface for the deposition of oriented Ba2YCu3O7-δ films. The conditions at which preferential (200) film alignment is obtained has been optimized. The ion-to-atom ratio and ion beam energy are critical in determining beam effects on in-plane alignment Pole figures revealed that both (220) and (111) in-plane alignments parallel to the direction of the ion beam could be obtained depending on the ion-to-atom ratio. Certain orientations dominate at various temperature regimes on different substrates. The orientation regimes were similar on all substrates, but the temperature at which the trends were observed differed with substrate. Microstructures were correlated to orientations, with the desired (200) orientation being columnar. A mechanism to account for this biaxial alignment is proposed.
An Initial Investigation of the Electrical and Microstructural Properties of Au/Ti and Au/Pd/Ti Ohmic Contact Structures for AlGaAs/GaAs HBTs
Authors: Sandhu Kuldip S. , Staton-Bevan Anne E. , Henry Bernard M. , Crouch Mark A. , Gill Sukhdev S. 
Published: March 2011

ABSTRACTThe electrical and microstructural properties of Au/Ti and Au/Pd/Ti contacts to p+-GaAs (C-doped, 5×1018cm−3) were investigated. Current-voltage measurements as a function of temperature showed that the Ohmicity of the Au/Ti contact improved upon annealing. However, the annealed binary contact featured Au spiking into the GaAs making it unsuitable for HBT applications. The addition of a Pd diffusion barrier layer between the Au and Ti metallisation layers prevented spiking, but resulted in a decrease in the Ohmicity of the contact.For all the contact systems it was found that thermionic-field emission dominates the current transport mechanism across the metal-semiconductor interface between the temperature range 198K and 348K. The Au/Pd/Ti contact structure shows HBT potential, however higher epilayer doping levels will be required to produce satisfactory specific contact resistivities.
Ohmic Contacts to p-Type InGaAs/InP with a Graded Bandgap Heterobarrier
Authors: Leech Patrick W. , Reeves Geoffrey K. 
Published: March 2011

ABSTRACTOhmic contacts to p-type InP with an In0.47Ga0.53As buffer layer and an interposed superlattice of 50 Å In0.47Ga0.53As/ 50 Å InP have been investigated. Initial studies of contacts to In0.47Ga0.53As/ InP without the superlattice structure have shown that Pd/Zn/Pd/Au metallization produced a lower specific contact resistance (pc = 1.1 × 10−4 Ω cm2) than Pd/Ge/Au, and over a wider range of anneal temperature than Au/Zn/Au. The incorporation of the superlattice in the p-In0.47Ga0.53As/ InP structure resulted in Pd/Zn/Pd/Au contacts with pc of 3.2 × 10−5 Ω cm2 as-deposited and 7.5 × 10−6 Ω.cm2 after a 500 °C anneal. The presence of Pd/Zn in the metallization was shown as important in reducing pc. Significant intermixing of the metal layers and In0.47Ga0.53As occured at ≥ 350 °C, as revealed by Rutherford backscattering spectrometry.
Initial Stage of Heteroepitaxial Growth of SiC on Si by Gas Source MBE Using Hydrocarbon Radicals
Authors: Fuyuki Takashi , Tarui Yoichiro , Hatayama Tomoaki , Matsunami Hiroyuki 
Published: March 2011

ABSTRACTHeteroepitaxial growth of 3C-SiC on Si in gas source molecular beam epitaxy ( GSMBE ) was carried out by a combination of carbonization of a Si surface and subsequent crystal growth on it using hydrocarbon radicals and Si2H6. The carbonization process and the initial stage of the subsequent growth during the intermittent supply of Si2H6 have been studied by a reflection high-energy electron diffraction (RHEED) observation. A Si surface was chemically converted to 3C-SiC at 750°C, and homoepitaxial growth on the carbonized layer could be obtained at 1000°C. Si atoms generated by thermal decomposition on a surface would react with hydrocarbon radicals, forming SiC through a layer by layer growth mode.
Alignment of Adsorbate-Induced Defects on Silicon(001) 2×1 Observed with STM
Authors: Seiple J. V. , Pelz J. P. 
Published: March 2011

ABSTRACTWe have observed that a build-up of gas-phase adsorbates on Si(001) followed by mild annealing at temperatures in the range 500 - 800°C can lead to a quasi-periodic array of line defects, which in STM images appear similar to lines of dimer vacancies aligned perpendicular to the surface dimer rows. These line defects can be eliminated by annealing at temperatures above 900°C, indicating that Ni contamination is not the cause. Adsorbed O2 or H2O followed by an anneal do not exhibit the same behavior.
Diffusion-Segregation Equation for Simulation in Heterostructures
Authors: Gafiteanu R. , You H.-M. , Göesele U. , Tan T.Y. 
Published: March 2011

ABSTRACTDiffusion of impurity atoms or point defect species occurs simultaneously with segregation in materials that are inhomogeneous or consisting of heterostructures. Based on thermodynamic principles, a general diffusion-segregation equation (DSE) simultaneously describing the species’ diffusion and segregation behavior has been derived. The DSE treats the diffusion-segregation problems on the same fundamental level as the diffusion problems are treated by Fick’s Laws. A critical comparison of modeling diffusion-segregation phenomena using the DSE vs. previous formulations is given. The wide range of applications of the DSE is demonstrated by several examples.
Control of Interfacial Mechanical Properties in Ti/Al203 Composites
Authors: Wang Hsin-Fu , Gerberich William W. , Angelo Jim E. , Mills Mike J. 
Published: March 2011

ABSTRACTThe fracture energy of Ti/Al203 composite interfaces has been determined by four point bending tests of sandwich specimens for different thicknesses of metal interlayers at 900°C. The interfacial fracture was found to be brittle. An intermetallic reaction product (Ti3Al) was produced at the interface after the diffusion bonding process. When the metal interlayer is thicker, there is more plastic energy dissipation in the metal during the fracture process. Therefore, the interfacial fracture energy increases. This can be seen from the fact that there is a larger plastic zone size with increasing thickness of the metal interlayer. The measured interfacial fracture energy Ti/Al203 ranges from 9.6 J/m2to 45.1 J/m2. The intrinsic interfacial fracture energy is obtained to be 0.26 J/m2. The embrittlement of the interface after the diffusion bonding process causes this value to be smaller than work of adhesion for Ti/Al203 (2.0 J/m2).
Influence of Segregation Effects on the Energies of Lead/Graphite and Gold/Graphite Interfaces
Authors: Gangopadhyay Utpal , Wynblatt Paul 
Published: March 2011

ABSTRACTThis paper reports the results of solid state wetting studies of graphite by Pb and Au alloyed with Ni. It is shown that additions of Ni ranging from 0 to 0.2 wt%Ni reduce the contact angle of Pb on graphite from 117 to 80°, and that a 5 wt% Ni addition to Au decreases the contact angle of Au on graphite from 131 to 123°. These contact angle changes are used to compute the interfacial energy at both Pb/graphite and Au/graphite interfaces. Direct evidence of Ni segregation at those interfaces is also obtained by crater edge profiling measurements. It is found that the enrichment factor of Ni is much larger in the Pb- than in the Au-based system. Also, for similar changes in interfacial energy, the effects of Ni segregation on contact angle are larger in the Pb- than in the Au-based system. These effects are discussed in terms of the relative surface and interfacial energies in the two systems.
Measurement of Plasticity Gradients with Scanning Probe Microscopy
Authors: Kiely James D. , Bonnell Dawn A. 
Published: March 2011

ABSTRACTScanning Tunneling and Atomic Force Microscopy were used to characterize the topography of fractured Au /sapphire interfaces. Variance analysis which quantifies surface morphology was developed and applied to the characterization of the metal fracture surface of the metal/ceramic system. Fracture surface features related to plasticity were quantified and correlated to the fracture energy and energy release rate.
Sputter Etching Effect on Magnetic Properties in TaOx/TbFeCo/Ag Layered Films
Authors: Shimamori Takumi , Yoshida Hidemi , Kobayashi Yoshimitsu 
Published: March 2011

ABSTRACTSputter etching effect on magnetic properties was investigated in TaOx/TbFeCo/Ag layered films. With sputter etching, smooth interfaces of about lnm roughness were obtained. In films with smooth interfaces, magnetization was stabilized and magnetization reversal was sharpened at around the Curie temperature. As a result, recorded marks were stabilized, and the media became sensitive to the magnetic field for writing. 49dB was obtained as C/N even at 0.45μm mark length, which is sufficient for digital recording.
The Influence of Grain-Boundary Structural Disorder on the Magnetic Properties of Nanocrystalline Nickel
Authors: Szpunar Barbara , Erb Uwe , Aust Karl T. , Palumbo Gino , Lewis Laurent J. 
Published: March 2011

ABSTRACTThe influence of grain boundaries on the magnetic properties of nanocrystalline nickel, in particular the ∑ = 3 and ∑ = 5 special grain boundaries and the extreme case of a purely amorphous sample, has been investigated. Our calculations reveal that the magnetic moment is rather insensitive to the structural disorder varying by at most 15 %. These results correlate extremely well with the recent observation in electrodeposited nickel that the magnetic moment depends very little on grain size, down to about 10 nm.
NH3-Plasma Treatment of Gaas Surface at High Temperature in Remote Plasma and Direct Plasma Reactor
Authors: Wan Park Kyoung , Jae Lee Seong , Shin Mincheol , Lee El-Hang 
Published: March 2011

ABSTRACTNH3-plasma treatment has been used for passivation of native-oxide-contaminated GaAs surface. Ex situ band-gap photoluminescence(PL) measurement shows enhanced intensity for the treated surfaces in direct plasma. Auger electron spectroscopy(AES) shows that the treated surface contains nitrogen atoms but no arsenic atoms, which leads us to speculate that the graded GaN thin layer was formed on the surface. Long-term stability of the enhanced PL intensity is attributed to the formation of GaN on the surface.
Electronic Structure of the ∑3[111] Grain Boundary and Doping Effect in Ni
Authors: Chongyu Wang , Dongliang Zhao 
Published: March 2011

ABSTRACTBased on the tight-binding bond recursion method, the energetics parameters of ∑3[111] grain boundary in nickel are investigated. The theoretical results indicate that the boron enhances interatomic energy between the host atoms, and between impurity and nickel atoms. Calculations of the energy of the grain boundary segregation show that boron, nitrogen, and phosphorus have the tendency to segregate onto the grain boundary and segregation property of boron is stronger than that of nitrogen and phosphorus.
Effects of Near Interfacial Microstructure on Interlaminar Fracture Toughness of Hybrid Metal-Polymer Composites
Authors: Grabilnikov Alexander S. , Zinevich Oleg M. 
Published: March 2011

ABSTRACTResults of detailed study on interlaminar fracture toughness of hybrid aramid-epoxy/aluminum laminate composites are presented. A fracture mechanics approach has been adopted and Mode-I, Mode-II tests for a wide range of loading rates have been used. Hybrid composite failure loci has been studied using SEM technique. Results were analyzed from the point of view of metal substrate/aramid fibre surface free energy effect on near interfacial (in the boundary layers) microstructure and fracture toughness of elastomer modified epoxy resins. It has been shown, that toughened epoxy resin morphology (rubber particles size and volume content) and, as a result, fracture resistance of the boundary layers were strongly dependent upon the adsorption processes, that could take place during adhesion contact formation and curing. To increase interfacial fracture toughness of hybrid composites due to the improvement of near interfacial resin microstructure and boundary layer fracture resistance, as for aluminum-epoxy and for aramid-epoxy failure loci, metal sheets/aramid fibres surface properties and interfacial residual thermal stresses should be optimized. The last result has been achieved by means of si lane primer treatment of aluminum laminates and tensile loading of cured composite.
Structural Imperfections in Ulrathin Oxides Grown on Hydrogen Terminated Silicon Surfaces
Authors: Hattori Takeo , Ohishi Kazuaki 
Published: March 2011

ABSTRACTThe initial stage of oxidation of 40wt-% NH4F treated Si(111) surface at 300 °C in dry oxygen with a pressure of 133 Pa and the subsequent oxidation at 600 and 800°C were studied. It was found from the analysis of Si 2p photoelectron spectra that non-uniform layer by layer oxidation proceeds at 300°C, while the layer by layer oxidation proceeds at 600 and 800°C. Furthermore, at these temperatures the interface becomes atomically flat with the progress of oxidation.
The Study of Silicon Diffusion into GaAs by Rapid Thermal Oxidation
Authors: Chen W. S. , Fu C. 
Published: March 2011

ABSTRACTThe diffusion of silicon into GaAs was investigated in this work. Shallow silicon carrier profile with doping levels in excess of 1018 cm−3 were obtained in GaAs by rapid thermal oxidation (RTO) of Si cap film in pure O2 with pressure 2 torr at 800 ∼ 900 ° C. SIMS revealed the presence of various degrees of interdiffusion in / near the interface between Si and GaAs as being a function of oxidation temperature and cap thickness. Ga and As atoms were observed in Si film. Silicon and oxygen were also found in the GaAs wafer. The silicon and arsenic atoms were segregated in / near the interface. The Si atoms could be driven further into GaAs by additional rapid thermal annealing (RTA) process. The above phenomena were confirmed by the electrical measurements taken on sheet resistance, doped dose, and mobility. The TaSix / GaAs Schottky barriers were also fabricated. The ideality factor, Schottky barrier height, and breakdown voltage are the functions of the doping level. This behavior could be accounted for by the theory of tunnel effect of Schottky barrier.
Surface Smoothing Process of YBa2Cu3O7−x Thin Film for Fabrication of Superconducting Multi-Chip Modules
Authors: Liang S. , Shi Z.Q. , Chern C. , Lu Y. , Safari A. , Lu P. , Kear B.H. 
Published: March 2011

ABSTRACTIn this paper, we report the development of surface smoothing process for YB2CU3O7. x (YBCO) films. The SrTi03/YBCO interface characteristics were investigated as functions of polishing agent and polishing time. It was found that the 7% HF solution gave the best results both in structural and electrical properties. The leakage current through the SrTiÛ3 film grown on polished YBCO was reduced to about 3 orders of magnitude. The dielectric constant was also increased from 110 to over 300. The superconducting properties of the YBCO bottom layer degraded insignificantly after undertaking the surface smoothing process and the overlayer growth of STO. This surface smoothing process without post treatment is suitable for subsequent growth of epitaxial STO films and the fabrication of MCM’s.
Conductive Polymer / Superconductor Sandwich Structures
Authors: Haupt Steven G. , Zhao Jianai , Lo Rung-Kuang , Zhou Ji-Ping , McDevitt John T. 
Published: March 2011

ABSTRACTMethods for characterizing the interface of conductive polymer/high-Tc superconductor sandwich structures are reported. Electrochemical procedures, such as cyclic voltammetry and chronoamperometry, are utilized to deposit conductive polymers directly onto bulk ceramic and thin film samples of YBa2Cu3O7-δ. Moreover, similar methods are utilized to cycle the polymer structures between their neutral (non-conductive) and oxidized (conductive) forms. Through changes in the polymer doping level, the superconducting properties of the high-Tc component can be modulated in a controllable and reproducible fashion. This paper focuses on an analysis of conductive polymer/superconductor interface phenomena as explored by electrochemical, resistivity vs. temperature and contact resistance measurements.
Biaxial State of Stress in SiGe Epilayers on Patterned Si Substrates
Authors: Fischer Armin , Richter Hans 
Published: March 2011

ABSTRACTWe present a two-dimensional analysis of the in-plane misfit stress and its elastic relaxation in rectangular patterned heteroepitaxial multilayer structures on rigid substrate. Based on the generally acknowledged model of relaxing film stress we calculate the distribution of the misfit stress versus distance from the free surface of a multilayered mesa edge. By superposition of the isolated stress fields of the mesa edges, we obtain the biaxial misfit stress distribution in a finite heteroepitaxial thin film structure on thick substrate. The formalism developed permits the determination of the variation of stress values as a function of material and size characteristics of the patterned multilayer-substrate system. The theoretical analysis will be applied to the SiGe/Si strained layer epitaxy and III-V compound semiconductor integration with Si or Ge.
Gels and Gel-Derived Glasses in the SiO2 GeO2 System
Authors: Mukherjee Shyama P. 
Published: March 2011

ABSTRACTGels and gel-monoliths in the SiO2 -GeO2 system were prepared by different procedures using metal alkoxides as starting materials. Several gel compositions with increasing GeO2 were prepared. Crystallization behavior of gels in relation to the preparation procedures, homogeneity, and molecular structure of gels is discussed. Supercritically dried porous gel-monoliths of high silica compositions were densified into glass by sintering at 1280°C.
Ferroelectric Ceramics--The Sol-Gel Method Versus Conventional Processing
Authors: Wu Edward , Chen K.C. , Mackenzie J.D. 
Published: March 2011

ABSTRACTThe sol-gel method for the preparation of ceramics and glasses has frequently been mentioned as more advantageous as compared to conventional methods. However, there are few known examples of a direct comparison for the same material. In the present work both the processing and resultant properties for ferroelectrics such as BaTiO3, KTaO3, KNbO3 and K(Ta,Nb)O3 made by both methods are directly compared. The uniformity is evaluated by high-angle x-ray diffraction, electron microscopy and EDAX and the dielectric properties are compared. The advantages and disadvantages of the sol-gel method are discussed.
Chemical Synthesis of Single and Mixed Phase Oxide Ceramics
Authors: Mazdiyasni K. S. 
Published: March 2011

ABSTRACTThermal and hydrolytic decomposition of metal alkoxides, M(OR)n, is employed to obtain ultra-high-purity submicron-size < 50 nm refractory, ferroelectric, and electro-optic oxide powders. The high surface activity associated with these powders makes possible relatively low temperature processing of the powder compacts to near theoretical density with uniform fine-grain-size bodies. Transmission electron microscopy, high-temperature X-ray, and infrared and Raman spectroscopy are used to observe nucleation, growth, crystallite morphology of the synthesized powder, and microstructural features.
Structure Data from Light Scattering Studies of Aerogel
Authors: Hunt Arlon J. , Berdahl Paul 
Published: March 2011

ABSTRACTThis paper reports a recent advance in the understanding of the structure of microporous optical materials such as aerogel through the interpretation of light scattering data. The Fourier transform of the densitydensity correlation function is used to relate measurements of the angular dependence of scattered light to material structure parameters. The results of the approach fit the unusual dependence of the intensity of scattered light as a function of angle for two polarizations. The fit shows that light scattering from aerogels may be interpreted as having two origins; one from the small scale structure of linked particles that comprise the material, and the second due to weak fluctuations in the average density of the microporous structure over distances significantly larger than the pore size.