bluuebunny/crossref_metadata_2025_split huggingface dataset:
Remote Plasma-Enhanced Chemical Vapor Deposition of Epitaxial Silicon on Silicon (100) at 150°C
Authors: Hsu T. , Anthony B. , Breaux L. , Banerjee S. , Tasch A. 
Published: March 2011

AbstractLow temperature processing will be an essential requirement for the device sizes, structures, and materials being considered for future integrated circuit applications. In particular, low temperature silicon epitaxy will be required for new devices and technologies utilizing three-dimensional epitaxial structures and silicon-based heterostructures. A novel technique, Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD), has achieved epitaxial silicon films at a temperature as low as 150°C which is believed to be the lowest temperature to date for silicon epitaxy. The process relies on a stringent ex-situ preparation procedure, a controlled wafer loading sequence, and an in-situ remote hydrogen plasma clean of the sample surface, all of which provide a surface free of carbon, oxygen, and other contaminants. The system is constructed using ultra-high vacuum technology (10-10 Torr) to achieve and maintain contaminantion-free surfaces and films. Plasma excitation of argon is used in lieu of thermal energy to provide energetic species that dissociate silane and affect surface chemical processes. Excellent crystallinity is observed from the thin films grown at 150°C using the analytical techniques of Transmission Electron Microscopy (TEM) and Nomarski interference contrast microscopy after defect etching.
Reaction Kinetics of Epitaxial Silicon Deposition at 220-400°C Using Remote Plasma-Enhanced Chemical Vapor Deposition
Authors: Anthony B. , Hsu T. , Breaux L. , Banerjee S. , Tasch A. 
Published: March 2011

AbstractIn this paper the reaction kinetics of Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD) are investigated. Growth rate characterization has been performed for substrate temperatures of 220 – 400°C, r-f powers from 4 – 8 W, and silane flow rates of 10 – 30 sccm. Growth rate has been found to increase exponentially with r-f power, which is, as yet, unexplained. An approximate square root dependence of growth rate on silane partial pressure agrees with the theory of Claasen et. Al for Chemical Vapor Deposition (CVD) of silicon from silane with an inert carrier gas. From an Arrhenius plot of the temperature dependence of growth rate, we note a change of slope at ∼300°C which we have attributed to the behavior of hydrogen at the silicon surface.
Development of Remote Plasma Enhanced Ohemical Vapor Deposition Processes Through the use of in Vacuo Electron Diffraction and Electron Spectroscopy
Authors: Rulder R. A. , Fountain G. G. , Hattangady S. V. , Posthill J. B. , Markunas R. J. 
Published: March 2011

AbstractRemote plasma enhancecd chemical vapor deposition techniques have been developed for a wide variety of processes. These include SiO2, Si3N4, Si, Ge, GaN, GaAs, and a-Si:H depositions. This development has been enabled through the use of electron diffraction and electron spectroscopy techniques. These techniques have been used to qualify cleaning procedures prior to epitaxial or dielectric depositions. They have beeii used to qualify epitaxial deposition conditions by defining suitable.temperature and rate conditions. And, they have been used to evaluate cross-contamination issues.In situtechniques have been used in conjunction withex situcharacterizations to identify and correct problems in wafer cleaning, epitaxy, and process integration.
Low-Temperature Pecvd Si3N4 Films for GaAs Encapsulation and Passivation.
Authors: Pfeffer R. L. , Gerardi G. J. , Lux R. A. , Jones K. A. , Poindexter E. H. , Chang W. H. , Devine R. A. B. 
Published: March 2011

AbstractWe have begun a detailed study of the physical properties of Si3 N4 films deposited at low temperatures using a PECVD process based on dilution of reactive gases with inert carrier gas [1] in order to investigate their feasibility for use as post-implant encapsulants and/or device passivation layers for GaAs. The films and substrates are analyzed by ion channeling, ellipsometry, IR spectrometry, ESR, RBS, and SEM to evaluate implantationinduced substrate and interface damage as well as the films’ optical properties, surface morphology, stoichiometry, uniformity, stress, and electrical trapping characteristics. Following furnace or RTA annealing they are recharacterized, adding SIMS to evaluate As diffusion into the films. Both Schottky and ohmic contacts are then formed and used to measure Hall mobility, trap density and 1/f noise. Preliminary results of these studies are presented and compared with those obtained using other techniques such as wafer-to-wafer As entrapment, arsine overpressure, or conventional CVD.
Pecvd RF Discharge Models Review
Authors: Garscadden Alan 
Published: March 2011

AbstractThis paper presents a concise and subjective summary of the rapid progress that has been made in the understanding of the essential features of RF discharges. The paper concentrates on introducing the important concepts used in modeling the rf discharge. The discharges have been modeled from several distinctly different approaches. These include circuit, beamdiffusion, plasma fluid or continuum, and particle kinetic models. The treatments have their usefulness depending on the application. The circuit models give easily parameterized results, power deposition, and phase angles between voltage and current, however, they do not describe the important plasma chemistry and the source terms for deposition and etching. The newer continuum models efficiently give self-consistent plasma parameters for higher pressure discharges but synergistic ion and neutral interactions with surfaces are difficult to include. The particle kinetic models can include many effects without approximations, however they need extensive data sets and long computer run times. The coupling of improved diagnostics and the different theories has resulted in a convergence of their conclusions. There are four distinct energy-gain mechanisms in the RF discharge : a bulk plasma excitation; electron beam excitation resulting from secondary emission from ion collisions with the electrodes; wave-riding acceleration on the sheath oscillation (collisional: Kushner); and a noncollisional plasma electron-sheath boundary interaction (Godyak). The relative contributions are sensitive functions of the gas mixture, pressure, frequency and RF voltage.
Radical and Molecular Product Concentration Measurements in CH4 RF Plasmas by Infrared Tunable Diode Laser Absorption
Authors: Wormhoudt J. 
Published: March 2011

AbstractInfrared tunable diode laser absorption studies of radicals and stable molecules formed in radio frequency plasmas are being carried out in a laboratory reactor which allows a long absorption path. In this paper we describe studies of CH4 RF plasmas. We report absolute concentration measurements as functions of total pressure and RF power for CH3 and C2H2 in CH4 plasmas, as well as measurements of the CH4 rotational temperature and dissociation fraction.
Plasma Deposition of SiNxHy: Process Chemistry vs Film Properties
Authors: Smith Donald L. 
Published: March 2011

AbstractThe chemistry of silicon nitride deposition from ammonia-silane and nitrogensilane mixtures in a glow-discharge plasma was analyzed using special mass spectrometric techniques involving line-of-sight sampling through an orifice in the wafer plane of a parallel-plate reactor. It was found that high rf power is needed to activate the nitrogen source sufficiently, and that silane flow must be held below a certain critical value to ensure an excess of activated nitrogen. This critical value is detectable by the appearance of disilane in the plasma, which is indicative of silane reacting with itself. At low power, silane reacts only with itself, and disilane is the dominant gaseous product. Conversely, disilane-free plasmas in either gas mixture result in films that are nitrogen-rich and free of the Si-H bonding that has been correlated with poor dielectric behavior. Utilization of silane to form SiNxHy is near unity. The aminosilanes, SiH4-n(NH2)n, are the sole gas-phase Si-N products of the ammonia mixture, and the triaminosilane radical, Si(NH2)3, is the key deposition precursor. The precursor is transformed into SiNxHy by way of a temperature-driven chemical condensation reaction at the surface, with the evolution of ammonia. The nitrogen mixture produces no gas-phase Si-N products, and deposition proceeds by the reaction of SiHn radicals and N atoms at the surface. These basic differences in deposition mechanism result in significant and logical differences in the physical and electrical properties of films deposited from the two mixtures.
Plasma Deposited Silicon Nitride Film Chemistry
Authors: Chiang Justin N. , Hess Dennis W. 
Published: March 2011

AbstractThe structure and composition of plasma deposited (PD) silicon nitride thin films formed using NH3/SiH4, N2/SiH4, and N2/SiH4/H2, discharges are compared. The effect of introducing a DC grounded stainless steel mesh between the parallel electrodes is also discussed. Chemical structure and composition of these films are measured using X-ray Photoelectron Spectroscopy and Fourier Transform Infrared Spectroscopy. Significant changes in film composition are observed with changes in gas composition and with utilization of the screen. When the screen is invoked, variations in film composition are more pronounced for PD silicon nitride films formed using N2 as the nitrogen source. An increase in the N:Si ratio occurs for all films deposited using the screen. This compositional change is reflected in increased N-H and decreased Si-H bonding. Similar changes are also observed in films deposited from a N2/SiH4/H2 discharge compared to films formed using a N2/SiH4 discharge.
Temperature Dependence of the Morphology of Thin Diblock Copolymer Films as Revealed by Neutron Reflectivity
Authors: Russell T. P. , Anastasiadis S. H. , Satija S. K. , Majkrzak C. F. 
Published: March 2011

ABSTRACTThe order-disorder transition in thin films of symmetric diblock copolymers of polystyrene and polymethylmethacrylate has been investigated by neutron reflectivity. At temperatures above the order-disorder temperature, TMST, a surface induced oscillatory segment density profile with an exponential decay length, χ, is observed. The inverse of decay length 1/≤ TMST a lamellar morphology oriented parallel to the surface propagates through the entire specimen.
Phonons at Martensitic Phase Transitions of bcc-Ti, bcc-Zr and bcc-Hf
Authors: Petry W. , Heiming A. , Trampenaux J. 
Published: March 2011

ABSTRACTInelastic neutron scattering on in situ grown bcc single crystals of the group 4 metals Ti, Zr and Hf show a band of low energy and strongly damped phonons. Geometrical considerations show how these damped lattice vibrations achieve the displacements necessary for the two martensitic phase transitions from bcc to ω(under pressure) and from bcc to hcp (upon lowering the temperature). The low energy and temperature dependent phonons are precursor fluctuations of the hcp or ω phase within the bcc phase.
Use of Neutron Diffraction in Determining Strains in High-Temperature Superconducting Composites
Authors: Kupperman D. S. , Singh J. P. , Majumdar S. , Faber J. 
Published: March 2011

ABSTRACTThe Argonne Intense Pulsed Neutron Source and General Purpose Powder Diffractometer have been used to study high Tc metal oxide composites composed of yttrium barium copper oxide and silver. Neutron diffraction techniques were applied to composites with 15, 20 and 30% silver content by volume. We have observed that after hot pressing, the 30% Ag specimens contained both orthorhombic high Tc and tetragonal, non-superconducting phases near the center of the specimens but only tetragonal near the surface. The relationship of shifts in Bragg peaks to strains of the constituents is discussed.
High Resolution Neutron Powder Diffraction Studies of the Ferroelastic Phase Transition in LaNbO4
Authors: David W I F 
Published: March 2011

ABSTRACTAnalysis of high resolution neutron powder diffraction data of ferroelastic LaNbO4 indicates a monoclinic to tetragonal structural phase transition that is accompanied by anomalous line broadening. The origins of this line broadening have been investigated using a novel modification of the Rietveld technique. The results show that strain broadening is associated with the ferroelastic phase transition both above and below the transition temperature. This anomalous ‘microstrain’ is well-described by a second rank strain tensor, the principal axes of which are collinear with the spontaneous lattice strain. This phenomenon may be a general feature of proper ferroelastic phase transitions.
Neutron Scattering from Lattice Defects
Authors: Peisl Johann , Dosch Helmut , Kirchner Stefan 
Published: March 2011

ABSTRACTFor O in Nb the experimental scattering distribution can be described by a so-called 3-force model. The scattering pattern exhibits close similarity to the one observed for the ω-phase in some bcc alloys. It is shown that the lattice distortion calculated from the proposed 3-force model contains static fluctuation of the ω-phase. The ω-phase is closely related to the minimum in the LA 2/3 (111) phonon dispersion branch. With decreasing temperature the frequency of this phonon decreases, whereas the elastic diffuse scattering at the same position increases. This “softening” of the lattice, together with an increasing “central peak”, gives an equivalent description of the situation.
Lattice Misfit and Decomposition in Ni-Al-Mo Alloys
Authors: Calderon Hector , Kostorz Gernot 
Published: March 2011

ABSTRACTThe effect of lattice mismatch δ between the γ-matrix and γ'-precipitates on the decomposition process of Ni-Al-Mo alloys has been investigated. The results show that for δ = 0 spherical precipitates are formed without any orientational correlation. For δ > 0 non-spherical particles, aligned along <100>, are produced. The kinetics of the γ-γ' decomposition becomes slower as δ is reduced to zero.
Non-Destructive Measurement of Residual Stresses in U-0.8 WT% Ti by Neutron Diffraction
Authors: Salinas-Rodriguez A. , Root J.H. , Holden T.M. , Macewen S.R. , Ludtka G.M. 
Published: March 2011

ABSTRACTThe macroscopic residual stress distribution in γ-quenched and stress levelled U-0.8wt% Ti alloy tubes was studied using neutron diffraction techniques. Residual strains were evaluated from the difference in d-spacings measured in the tubes and in small reference samples machined from each tube. Residual stresses were calculated with the isotropic bulk values of the elastic constants for polycrystalline α-U. Quenching from the γ field resulted in a nearly equi-biaxial stress state at every point across the wall thickness of the tube. The magnitude of the radial stress was very small compared with that of the axial and hoop stresses which were compressive at the surfaces and tensile in the interior. Stress levelling relieved almost completely the hoop residual stress without affecting the radial stress. The axial residual stress becomes tensile through the wall thickness and remains constant at about 20% of its magnitude in the as-quenched condition.
The Measurement of Boron at Silicon Wafer Surfaces by Neutron Depth Profiling
Authors: Downing R.G. , Lavine J.P. , Hossain T.Z. , Russell J.B. , Zenner G.P. 
Published: March 2011

ABSTRACTThe thermal neutron reaction 10B(n,α)7Li is used to measure the boron concentration on the surface of silicon wafers. The technique, referred to as neutron depth profiling (NDP), requires no special sample preparation. Boron is determined on the as- received wafers at a level of 1012 to 1013 atoms/cm2. A boron level of about 2×1012 atoms/cm2 is found at the wafer surface after oxidation, epitaxial, or polycrystalline silicon deposition. Additional measurements are given from SIMS measurements of multilayer structures on silicon also showing the presence of boron. Ambient air appears to be a significant source of the boron.
Dynamics of Weakly Connected Solids: Sintering of Polymeric Aerogels
Authors: Schaefer D. W. , Richter D. , Farago B. , Brinker C. J. , Ashley C. S. , Olivier B. J. , Seeger P. 
Published: March 2011

ABSTRACTA combination of small angle scattering (SAS) and neutron spin-echo (NSE) spectroscopy is used to characterize the structure and dynamics of polymeric silica aerogels during sintering. The SAS data indicate that densification at short length scales precedes the densification at longer scales (comparable to that of the pore structure). Interpreted within the fracton model, the NSE data are consistent with an initial decrease in connectivity during relatively early stages of densification.
Inelastic Neutron Scattering Studies of Nonlinear Optical Materials: p-Nitroaniline Adsorbed in Alpo-5
Authors: Nicol Jacqueline M. , Udovic Terrence J. , Rush J.J. , Cox Sherman D. , Stucky Galen D. 
Published: March 2011

ABSTRACTInelastic neutron scattering has been used to characterize the vibrational spectroscopy below 220 meV of para-nitroaniline adsorbed in the molecular sieve ALPO-5. Samples at loadings of both 3 and 13 weight %, which represent the onset of and the maximum in the nonlinear optical properties respectively, were studied. The torsional vibration of the amino (NH2) group has been identified at ca. 50 meV. The splitting and structure of this mode is sensitive to the loading level. This can be related to differences in the nature of the hydrogen bonding in these materials.
Thermal Expansion of Graphite and HNO3-Graphite Intercalation Compounds, a Neutron Diffraction Study
Authors: Pinto Haim , Melamud Mordechai , Shaked Hagai 
Published: March 2011

ABSTRACTThe temperature dependent lattice parameter, c(T), was determined for samples of graphite, and HNO3 -graphite intercalates stage 3 and stage 4, using neutron diffraction. The temperature range studied is 12 to 300 K. The stage 3 and stage 4 intercalates exhibit a strong two-step discontinuity at the temperature of their structural phase transition (≈260 K). A stage-independent, temperature-dependent lattice parameter for the intercalant layer is extracted from the observed lattice parameters for graphite, stage 3, and stage 4 intercalates. The graphite and the intercalant lattice parameters are calculated using one-dimensional Debye theory in the framework of the Grüneisen relation. The Debye temperatures that yield best fits to the observed lattice parameters of the graphite and the intercalant are 500 K and 421 K, respectively. Using these values, thermal expansion coefficients for graphite, the intercalates and the intercalant are derived.
Neutron Powder Diffraction: A Powerful Materials Research Technique
Authors: David W I F 
Published: March 2011

ABSTRACTNeutron powder diffraction is a powerful technique that provides a detailed description of moderately complex crystal structures. This is nowhere more apparent than in the area of high temperature superconductors where neutron powder diffraction has provided precise structural and magnetic information, not only under ambient conditions but also at high and low temperatures and high pressures. Outside superconductor research, the variety of materials studied by neutron powder diffraction is equally impressive including zeolites, fast ionic conductors, permanent magnets and materials undergoing phase transitions. Recent advances that include high resolution studies and real-time crystallography will be presented. Future possibilities of neutron powder diffraction will be discussed.
Small Angle Neutron Scattering Study of Critical Binary Fluids in Porous Glasses
Authors: Dierker S. B. , Wiltzius P. 
Published: March 2011

ABSTRACTWe present small angle neutron scattering measurements of the static structure factor S(q) of the binary fluid mixture water-lutidine imbibed into the porous glass Vycor as a function of temperature and composition. S(q) changes from a Lorentzian in the one phase region to a Lorentzian squared at the random field transition. The correlation length increases from ∼ 20 A in the one phase region to to ∼ 52 Å (≈ pore diameter) in the frozen domain state.
Gas Density in Helium Bubbles in Nickel and Iron Determined by Small Angle Neutron Scattering
Authors: Schwahn D. 
Published: March 2011

ABSTRACTA general discussion of the gas density determination of He bubbles in Ni and Fe with neutron scattering using the contrast variation method is given. One finds, that best results are obtained using isotope combinations for Ni, and magnetic and nuclear scattering for Fe. An experiment to determine the density of He in Ni demonstrates the applicability of this method.
Microstructure and Isotopic Labeling Effects on the Miscibility of Polybutadiene Blends Studied by the Small-Angle Neutron Scattering Technique
Authors: Han Charles C. , Hasegawa Hirokazu , Hashimoto Takeji , Hargis I. Glen , Aggarwal S. L. 
Published: March 2011

ABSTRACTDeuterated polybutadiene and protonated polybutadiene (PBD/PBH) blends with various microstructures have been studied by the small-angle neutron scattering experiments. Correlation length, ξ, zero-wavenumber structure factor, S(q=o), and interaction parameter, Xblend have been obtained. All PBD/PBH blends exhibit UCST behavior. With the use of random copolymer theory, the interaction parameter, Xblend, has been successfully separated into X1, X2 and X3 which are interaction parameters between the same isotope labeled 1,2-unit and 1,4-unit, opposite isotope labeled 1,2-unit and 1,4- unit, and opposite isotope labeled 1,2-unit with 1,2-unit or 1,4-unit with 1,4-unit, respectively.
The Application of Neutron Topography to the Study of X-ray Sensitive Organic Crystals - a Possible Alternative to X-ray Topography.
Authors: Dudley M. 
Published: March 2011

ABSTRACTNeutron topography has been carried out on organic single crystals of varying Xray sensitivity, in order to test the feasibility of the technique as an alternative to X-ray topography for the study of the influence of defects on the solid state reactivity of X-ray sensitive single crystals. Specimens studied include the diacetylene PTS, and Pyrene. A comparison of the strain sensitivity and spatial resolution of the neutron and X-ray based techniques is made. Preliminary results of dynamic neutron topographic studies of the UV induced polymerization in PTS are presented. These results are compared to those obtained from similar X-ray topographic studies.Results indicate that the neutron technique can be a useful ally technique to the analogous X-ray techniques in studies of the influence of defects on reactivity in specimens of moderate X-ray sensitivity. In cases of extreme sensitivity, the neutron technique is the only one available for studies of this nature.
A Small Angle Neuitron Scattering Investigation of Compacted Nanophase TiO2 and Pd
Authors: Epperson J. E. , Siegel R. W. , White J. W. , Eastman J. A. , Liao Y. X. , Narayanasamy A. 
Published: March 2011

ABSTRACTNanocrystalline compacts of TiO2 and Pd were prepared by first condensing the Ti or Pd vapors in an inert gas atmosphere. The Ti was oxidized in situ to TiO2. Samples were prepared by scraping off and compacting the nanophase materials into thin disks. The small angle neutron scattering was measured in the as-prepared condition and after isothermal anneals of up to 23 hrs at 550°C for the TiO2 and up to 3.3 hrs at 300°C for the Pd. Scattering data were obtained in absolute cross sections. Integrated small angle scattering and maximum entropy methods were used in estimating the structural parameters. The results are interpreted in terms of a model which consists of nanometer sized grains of the materials separated by boundary regions which are, on average, much less dense than the respective bulk materials; 21% for the TiO2 and about 56% for Pd. However, the boundary regions contain voids or pores, which contribute to these density decrements. Possible sources of error are discussed.