bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrasonic Characterization of Thin Adhesive Bonds
Authors: Dickstein P. , Sinclairw A. N. , Segal E. , Segal Y. 
Published: March 2011

AbstractA series of nondestructive and destructive tests were performed on samples of aluminumto-aluminum bonded plates. The specimens featured a range nominal thickness of the adhesive layer from 0.0 up to 0.5 mm. It was found that a commercial bondtester was inappropriate for assessing the thickness of the adhesive in this range. However, the frequency peak of an ultrasonic echo signal from the adhesive layer was a reliable indicator of bond thickness. It is proposed that nondestructive assessments of the bond thickness could serve as an indicator of the longterm resistance of the adhesive to water ingress and bond degradation.
Nondestructive Evaluation of Thin Film Microstructures by Picosecond Ultrasonics
Authors: Maris Humphrey J. , Grahn Holger T. , Tauc Jan 
Published: March 2011

AbstractWe describe a technique by which ultrasonic measurements can be made in the picosecond time domain. A light pulse (duration of the order of 0.1 psec) is absorbed at a surface, thereby setting up an elastic stress. This stress launches an elastic pulse into the interior. The propagation of this strain, including its reflection at interfaces within a microstructure, is monitored through measurements of the time-dependent changes of the optical reflectivity. These measurements are made using a time-delayed probe pulse. In these experiments the spatial length of the elastic pulses can be as short as 50 Å. We can therefore use this technique to perform a nondestructive ultrasonic evaluation of thin-film microstructures. We describe here results we have obtained which demonstrate the application of the method to the study of the mechanical properties of thin films, the geometry of microstructures, and the quality of bonding at interfaces.
Materials Properties Characterization in Fossil-Fuel Power Plants
Authors: Gehl S. M. , Viswanathan R. , Townsend R. D. 
Published: March 2011

AbstractSignificant changes in microstructure occur in many fossil plant components that operate for long times at elevated temperatures. Some examples include hydrogen damage in steam-generating boiler tubes, carbide coarsening in superheater tubes, creep cavitation in the heat-affected zones of thick-section weldments, and temper embrittlement in turbine rotors and disks. Quantitative estimates of the remaining useful lives of components affected by these damage mechanisms require that the degree of damage be determined and related to the life-limiting mechanisms.The paper discusses recent progress in the development and field demonstration of nondestructive techniques for characterizing the damage types listed above. This research has produced several products that have achieved or are close to commercial status. The research has also helped to define some of the limitations related to access, sensitivity, and signal interpretation of the nondestructive techniques. The paper discusses how these limitations can often be mitigated by using several nondestructive techniques in concert to obtain a more complete picture of material condition or by removing small specimens for detailed laboratory analysis.
Some Industrial Applications of Grazing Incident Exafs Techniques
Authors: Dring I. S. , Oldman R. J. , Stocks A. , Walbridge D. J. , Falla N. , Roberts K. J. , Pizzini S. 
Published: March 2011

AbstractAn instrument to undertake grazing incident EXAFS has been developed. This is discussed along with some applications of its use on industrially important systems.
White Beam Synchrotron Topographic Studies of the Effects of Localized Stress Fields on the Kinetics of Single Crystal Solid State Reactions.
Authors: Dudley Michael 
Published: March 2011

AbstractWhite Beam Synchrotron Topography has been used to determine the role of localized stress fields in the solid state polymerization of single crystals of the diacetylene PTS. Results indicate that the stress fields due to grown in dislocations can accelerate local reaction kinetics in thermally induced polymerization reactions, although no such effects were previously observable in photolytically or radiolytically induced reactions. Results are analyzed in an analogous fashion to the treatment of the nucleation of solid state phase transformations at dislocations. Good agreement was found between approximate theoretical treatments and experimental observation. The response of the monomer crystal to the inhomogeneous stresses generated as a result of inhomogeneous reaction and the implications regarding local reaction kinetics are discussed in detail.
Fluctuating Interfaces: a Series of Synchrotron X-Ray Scattering Studies of Interacting Stacked Membranes
Authors: Safinya C. R. 
Published: March 2011

AbstractIn this paper we concentrate on fluctuation phenomena encountered in interacting multilayered fluid membranes using synchrotron x-ray scattering as the primary tool. These systems consisting of surfactant or lipidic surfaces, are prototype models for understanding the statistical behavior of fluctuating surfaces embedded in three-dimensions. In elucidating the nature of fluid membranes we stress a unique intrinsic property: in contrast to usual surfaces with finite shear moduli, where surface tension plays a central role, the free energy of these essentially tensionless surfaces is governed by their geometrical shape and its fluctuations. We present data in a new regime of stability for very dilute and flexible membranes with interlayer separations of order hundreds of Angstroms. This is in contrast to most rigid membranes where the interlayer interactions are dominated by detailed microscopic interactions such as hydration and van der Waals. We show that the stability of these dilute lamellar phases is associated with violent out-of-plane fluctuations of the membranes giving rise to an effectively large long-range repulsive interaction theoretically elucidated by Helfrich. Because of its entropic origin, this interaction is universal and we present data for two different surfactant systems. Finally, we show that this new regime is distinct from the classical regime in which largely separated membrane sheets are stabilized because of their mutual electrostatic repulsion.
Convection Effects in Epitaxial Reactors: an Experimental and Theoretical Study
Authors: Chinoy P. B. , Agnello P. D. , Ghandhia S. K. 
Published: March 2011

ABSTRACTAn experimental and theoretical study has been undertaken of the effects of natural and forced convection in horizontal epitaxial reactors. The epitaxial growth of GaAs was used as the experimental vehicle for this study. A mathematical model for mass, momentum and energy transfer in the reactor was developed. Excellent correlation between modeled and experimental results was demonstrated over a wide range of reactor pressures and susceptor geometries. Recirculation of hot gases, caused by natural convection, was found to result in a strong pressure dependence of growth rate at higher susceptor slopes. Low reactor pressures have been shown to be a more effective way to eliminate recirculation than high gas flow rates.
X-Ray Diffraction Analysis of Heteroepitaxial Cd1-yZnyTe on GaAs
Authors: Johnson S. M. , Ahlgren W. L. , Smith M. T. , Johnston B. C. , Sen S. 
Published: March 2011

ABSTRACTX-ray diffraction techniques were used to evaluate Cd1-yZnyTe grown on GaAs substrate orientations of {100}2°, {111}, {012}, and {123}. High-quality layers having compositions at or close to the CdTe and ZnTe binary end points can be grown on GaAs, but most of the ternary compositions have extremely broad rocking curves. Layers grown on {123} and {012} were found to have large tilts toward {111} about <121> that varied systematically with the lattice mismatch; this is consistent with the mismatch being accommodated by the formation of a low-angle tilt boundary at the interface. {111} layers were found to be twinned, and thus {100}2° and {123} appear to better suited for vapor-phase epitaxial growth (VPE). High-resolution x-ray diffractometer measurements showed that the lattice mismatch is almost entirely taken up by plastic deformation, and only a small tetragonal distortion was measured. CdTe was distorted more than ZnTe, and a greater distortion was measured for layers grown on {100}2° than on {111}, in agreement with estimates made using bulk elastic constants.
Atomic Abruptness and Smoothness at Heterointerfaces: Fact or Fiction?
Authors: Ourmazd A. , Kim Y. 
Published: March 2011

ABSTRACTIt is now common to claim the fabrication of heterointerfaces, which are atomically flat over distances in the micron range. However, when chemical lattice imaging and digital pattern recognition are combined to examine quantitatively individual semiconductor heterointerfaces of the highest quality, substantial atomic scale roughness is observed. In this paper we review the application of chemical imaging and pattern recogntion techniques to the characterisation of heterointerfaces at near-atomic resolution, and discuss the possible ways the results can be combined with optical measurements to give an overall picture of interfacial roughness.
Defects Related to Mixing Behavior of Highly Silicon-Doped GaAs/AlAs Superlatitices
Authors: Theodore N. D. , Carter C. B. , Mei P. , Schwarz S. A. , Harbison J. P. , Venkatesan T. 
Published: March 2011

ABSTRACTThe mixing of highly silicon-doped GaAs/AlAs superlattices as a result of annealing has been investigated by transmission electron microscopy and secondary ion mass spectrometry. As silicon doping-levels were raised in this study to 1019 cm−3 and 1020 cm−3 defects such as prismatic dislocation loops and Si-rich precipitates were observed to occur in the superlattices upon annealing. A correlation has been observed between the presence of particular defects and the inhibition of dopant-enhanced superlattice mixing.
Heteroepitaxial Growth of High Quality GaAs Films on Rapid-Thermal-anealing Processed CaF2/Si(511) Structures
Authors: Asano Tanemasa , Ishiwara Hiroshi , Furukawa Seijiro 
Published: March 2011

ABSTRACTHeteroepitaxial growth of CaF2 films on (511)Si and GaAs films on CaF2/Si(511) structures is investigated. CaF2 films and GaAs films are grown by vacuum evaporation and molecular beam epitaxy, respectively. Ion channeling measurements and replica transmission electron microscopy show that CaF2 films having good crystalline quality and surface steps can be formed by annealing at 900°C for 30 sec after the growth at 550° C. GaAs films having smooth surfaces and good crystalline quality can be grown on the annealed CaF2/Si(511) structures.
High Quality GaAs on Si and its Application to a Solar Cell
Authors: Ohmachi Yoshiro , Kadota Yoshiaki , Watanabe Yoshio , Okamoto Hiroshi 
Published: March 2011

ABSTRACTEpitaxial growth using thermal annealing and a strained layer superlattice is studied to obtain high-quality GaAs device layers on Si substrates. Crystalline quality of GaAs-on-Si is found to improve with thermal cyclic annealing at temperatures higher than the growth temperature and cooling down to 300°C. It is also found that the optimum InGaAs/GaAs strained layer superlattice buffer structure is one whose total thickness is several times the calculated critical thickness for the average In-mole fraction of the SLS buffer. Configurations and structures of dislocation reductions are ex-amined by TEM observations. A GaAs solar cell is successfully constructed and is found to show total area efficiencies of 18.3% under AM 0 and 20.0% under AM 1.5 conditions.
Plasma-Assisted Epitaxial Growth of GaAs on SI
Authors: Gao Qing Zhu , Hariu Takashi , Ono Shoichi 
Published: March 2011

ABSTRACTLow temperature cleaning process of Si surface and the subsequent epitaxial growth of GaAs on Si by Plasma-Assisted Epitaxy in hydrogen plasma are described. As the rf power applied to excite the plasma is increased, the temperature for both cleaning and epitaxial growth processes can be reduced. Then GaAs epitaxial layers were directly grown on Si at 440°C.
The Effects of Capless Face-to-Face Annealing Temperature and Time on the Properties of Silicon Implanted Gallium Arsenide
Authors: Paz Oded 
Published: March 2011

ABSTRACTMaintaining As overpressure during capless post-implantation annealing through the use of the face-to-face proximity configuration has proved to be a reproducible technique with less process parameters to control than the alternative techniques of capped or arsine annealing. An investigation of carrier mobility and dopant activation as a function of annealing temperature resulted in an optimum annealing temperature of 840 °C with activation improving for 9 min heat-up time as compared to a 14 min heat-up time. An increase in activation with anneal time during isothermal annealing was also observed. Dopant redistribution during annealing was modeled with an experimentally derived diffusion coefficient of 2×10−14 cm2/sec. This value is close to the diffusion coefficient published for capped annealing. Dopant redistribution in the near-surface (1000 Å) region was verified using SIMS. Based on presently available data there is no evidence for similar dopant redistribution during capless arsine annealing and this redistribution probably occurs whenever excess vacancy generation/redistribution is taking place, as during capped annealing and during proximity annealing.
Depth Oscillations of Planar Channeling Yields in InP and GaP for Lattice Location Applications.
Authors: Swanson M.L. , Parikh N.R. , Sandhu G.S. , Frey E.C. , Zhanc Z.H. , Chu W.K. 
Published: March 2011

ABSTRACTFor compound semiconductors with the diamond structure, (111) planar channel walls contain different atomic species when viewed from different sides; thus under channeling conditions, the yields of ions backscattered from the different species oscillate with depth in opposite senses for ion beams directed towards the different channel sides. We have studied this effect for 2 MeV He ions in a (111) channel of InP crystals. The application of this channeling phenomenon to the determination of the lattice sites of solute atoms was demonstrated for implanted In and Sb atoms at different depths in GaP.
New Growth Chemistries and Techniques in Metal-Organic Vapor Phase Epitaxy
Authors: Kuech T. F. 
Published: March 2011

ABSTRACTThe metal-organic vapor phase epitaxy (MOVPE) technique is perhaps themost versatile of the conventional III–V growth epitaxial systems. This versatility stems from the wide variety of chemical precursors available for the growth and doping of the films. Two examples of this versatility, carbon doping and selective epitaxy, are presented. Future progress within this technology will continue to be driven by the development of new chemistries.
Channeling of Shallow Si Implants Into GaAs as a Function of Tilt and Rotation Angles
Authors: Hovel Harold J. , McKoy T. E. , Mitcheli J. M. , Scilla G. , Moorea S. J. , Cardone F. 
Published: March 2011

ABSTRACTThe effects of tilt and rotation angle on implant channeling are explored for Si implants into (100)-oriented GaAs substrates using Monte Carlo simulations, SIMS profiling, capacitance profiling, and Hall measurements. It is shown that the 7° tilt angle often used to prevent axial channeling is not large enough, and 11–13° angles are required to obtain the sharpest and most reproducible implant profiles. Rotation angles have a much smaller effect on the profiles as long as the beam incidence is kept away from the < 110 > direction.
Study of Layer Disordering in MeV Si Implanted GaAs/AlGaAs Superlattices.
Authors: Chen Samuel , Lee S.-Tong , Braunstein G. , Rajeswaran G. 
Published: March 2011

ABSTRACTLayer intermixing in MeV Si-implanted quantum well superlattices (SLs) has been studied by transmission electron microscopy, secondary ion mass spectrometry and Rutherford backscattering spectroscopy. Molecular beam epitaxially grown GaAs(200Å) - Al0. 5Ga0.5As(200Å) SLs were implanted with 1 MeV Si+ at doses between 3 × 1014 and 1 × 1016/cm2. The implanted SLs were either furnace annealed at 850°C for 3 hr or rapid thermally annealed at 1050°C for 10 sec, both under GaAs proximity capping conditions. Totally mixed regions were observed only for the SLs implanted with 1 × 1016 Si/cm2 and then furnace annealed at 850°C for 3 hr. For the same dose, the RTA annealed SLs only showed slight layer intermixing. At lower doses, no appreciable intermixing was detected in either furnace or RTA annealed samples. By contrast, under either annealing condition extensive intermixing has been demonstrated for lower energy (220 keV) implantation, but at doses almost two orders of magnitude lowerl XTEM showed that in all the annealed samples, a defect-free zone existed in the near-surface region, followed by a band of secondary defects, with the maximum density located at about 1 μm below the surface. In the disordered samples, the position of the intermixed layers correlated with the defect band maximum. Under both annealing conditions, Si concentration profiles only showed slight broadening, and they correlated with the distribution of secondary defects as well as with the depth of the intermixed layers. The effects of dynamic annealing and surface on the implantation energy dependence, i.e., MeV vs. keV, of layer intermixing are discussed.
Effects of Rapid Thermal Anneals on Boron Implanted GaAs
Authors: Bowman R. C. , Adams P. M. , Herman M. H. , Buttrill S. E. 
Published: March 2011

ABSTRACTRaman scattering, double-crystal x-ray diffraction, and electron beam electroreflectance have been used to assess the damage produced in undoped (100)-GaAs by boron ion implants and the influence of post-implant anneals. Both conventional furnace and rapid thermal annealing treatments were found to remove much of the lattice strain created by the implants. However, considerable disorder also remains after these anneals.
Disordering of Si-Implanted GaAs-AlGaAs Superlattices by Rapid Thermal Annealing
Authors: Lee S.-Tong , Braunstein G. , Fellinger P. , Rajeswaran G. 
Published: March 2011

ABSTRACTWe have studied the disordering phenomenon in GaAs-AlGaAs superlattices induced by Si implantation followed by rapid thermal annealing. Layer intermixing has been detected in superlattices implanted with 220 keV Si+ at doses ≥ 1×l015 cm−2 and annealed at 1050°C for 10 s. The amount of intermixing saturates with time after 10 s annealing, whence the lattice damage caused by the implantation is predominantly annealed out. The transient disordering is attributed to defect-induced layer intermixing occurring during the annealing of the implantation damage. Concurrent with the disordering, Si diffusion is observed to be minimal, which indicates that layer intermixing due to Si diffusion and other impurity effects lags behind that due to defects in the time scales of the present experiment.
Electrical Damage Introduced in GaAs by Reactive Ion Etching using CH4/H2 mixture
Authors: Collot P. , Gaonach C. , Proust N. 
Published: March 2011

ABSTRACTElectrical characterizations (I–V,C–V) of TiPtAu/n-type GaAs Schottky diodes were performed in order to investigate the electrical damage introduced by CH4JH2 RIE. The effective barrier height measured according to the thermionic conduction model decreases from 0.79 eV to 0.53 eV after RIE carried out at 1.3 W/cm2.Recovery of the control I–V characteristics requires a wet chemical removal of 50 nm of the dry etched surface.Doping profiles, derived from conventional C–V analysis at 80 K and 300 K, show a decrease in free carrier concentration within 500 nm from the surface. Hall measurementsbetween 4 K and 300 K show an increase in carrier mobility after RIE. These effects are essentially attributable to chemical neutralization of the silicon dopants by hydrogen. Thermal annealing at 360°C leads to an almost complete recovery of the electrical activity and of the control Schottky barrier height.
The Effect of Ar Sputtering on the Disordering of AlGaAs/GaAs Multiple Quantum Wells
Authors: Shieh C. , Colvard C. , Mantz J. , Alavi K. , Engelmann R. 
Published: March 2011

ABSTRACTThe effect of Ar sputtering, in combination with different dielectric cappings, on the disordering of AlGaAs/GaAs multiple quantum wells was studied. It was found that the combination of Ar sputter etch and SiO2 capping provided the strongest enhancement in disordering. This effect generates enough change in refractive index to produce an index guided laser.
A Comparative Study of Thin-Film and Bulk Reaction Kinetics and Diffusion Path: the Ir/GaAs System
Authors: Schulz Kevin J. , Chang Y. Austin 
Published: March 2011

ABSTRACTControl of the structure and chemistry at the interfaces of compound semiconductors is essential for the commercial use of these materials in electronic and optical technologies. This can only be achieved when the governing thermodynamics and kinetics of interfacial reactions are understood. Based primarily on the experience of metal/Si interactions, however, a prevailing belief was born that thin-film reactions follow a separate set of thermodynamic and kinetic “rules” which are different from bulk reactions. The intent of our work has been to not only characterize metal/GaAs contact reactions but also to rationalize these reactions with equilibrium phase diagrams and bulk metal/GaAs diffusion couple experiments. Through this approach, a better understanding of thin-film and bulk differences has been obtained.The Ir/GaAs system is used as an example. Phase formation and reaction kinetics were studied for 30 nm Ir films on (100) GaAs using TEM, XTEM, and AEM. Bulk diffusion between 0.25 mm thick Ir foil and (100) GaAs wafers was studied with SEM and electron probe microanalysis (EPMA). The diffusion paths and kinetics were the same for thin-film and bulk. The phase sequence Ir/IrGa/IrAs2/GaAs formed for all diffusion couples. Reaction kinetics were parabolic with an activation energy of 3.0 eV for both thin-film and bulk, and the data was colinear in an Arrhenius plot. Reacted layer morphology in both cases was layered. The effects of grain size, crystallographic texturing, and the relative diffusivities of the components on the reaction mechanisms in bulk versus thin-film reactions are considered.
Cobalt-Germanium Contacts to n-Type GaAs Electrical and Metallurgical Aspects
Authors: Genut M. , Eizenberg M. 
Published: March 2011

ABSTRACTThe correlation between the microstructure and phase formation, and the electrical properties for the Co/GaAs, Co/Ge/GaAs and Ge/Co/GaAs systems have been studied. The microstructural analysis was carried out by transmission electron microscopy, and the component redistribution was determined by Auger electron spectroscopy. The electrical properties (Schottky barrier height and contact resistivity) were studied by means of current-voltage and capacitance-voltage measurements.
Growth and Characterization of Single Crystal Epitaxial CoGa on MBE Grown III-V Semiconductors
Authors: Garrison K. C. , Palmstrøm C. J. , Bartynski R. A. 
Published: March 2011

ABSTRACTWe have demonstrated growth of high quality single crystal CoGa films on Ga1−xAlxAs. These films were fabricated in-situ by codeposition of Co and Ga on MBE grown Ga1−xAlxAs(100) surfaces. The elemental composition of the films was determined using Rutherford Backscattering (RBS) and in-situ Auger analysis. The structural quality of the films' surfaces was studied using RHEED (during deposition) and LEED (post deposition). RBS channeling was used to determine the bulk crystalline quality of these films.For ∼500 Å CoGa films grown at ∼450°C substrate temperature, channeling data showed good quality epitaxial single crystals [χmin ∼7%] with minimal dechanneling at the interface.