bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study of High Temperature Damage Processes Using Microradiography
Authors: Benci J. E. , Pope D. P. 
Published: March 2011

AbstractSynchrotron radiation and microradiographic techniques were used to study the development of creep damage in notched tensile samples. The creep damage in these samples was recorded using microradiography. The density and distribution of creep damage was measured from the microradiographs using an image analysis system. The results from the image analysis can be compared to damage predictions from finite element models of the damage process to determine the quality of these models.Notched tensile samples of copper, iron and a low alloy steel were subjected to slow strain rate tensile tests at 500°C or 700°C. The tests were interrupted after various fractions of the creep lives had been expended. 1 mm thick longitudinal sections were then removed from the center of each sample for microradiography using electro-discharge machining.Creep damage in the copper alloy was concentrated in a fairly narrow band around the plane of minimum cross-section in the samples. This is in stark contrast to the results from iron and the low alloy steel. The creep damage in these materials developed at fairly sharp angles to the notch or crack plane. These results show that the damage process in iron and this steel is controlled by the equivalent stress while the formation of damage in copper is controlled by the maximum principal or hydrostatic stress.
Dynamic Cure and Diffusion Monitoring in Thin Encapsulant Films
Authors: Day David R , Shepard David D. 
Published: March 2011

AbstractRecent developments in the area of microelectronics now enable the fabrication of microdielectric sensors that can follow the drying, curing, and diffusion phenomena in thin films. This paper first investigates the response of the rricrodielectric sensor to cure in a thin epoxy film. The multi-frequency loss factor data are reduced to a single “ion-viscosity” response curve representative of the change in ion mobility during the cure reaction. The dynanic dielectric data are compared to Tg as a function of time as determined by differential scanning calorimetry (DSC) on several partially cured samples. The dielectric response is shown to be extremely sensitive to the entire cure process. A similar epoxy film is exposed to alternately wet and dry environments while the dielectric response is monitored. The diffusion coefficient of water in the cured resin is estimated through the dynamic change in permittivity using a simple Fickian model and the results are shown to be in good agreement with the literature values. Finally, changes in dielectric properties of a photoresist during UV exposure are presented.
Ultrasonic Monitoring of Polymer Properties from the Melt to the Solid State: Influence of Chemical/Structural Details
Authors: Piché L. , Lessard G. , Massines F. , Hamel A. 
Published: March 2011

AbstractAn ultrasonic technique is described for the simultaneous measurement of specific volume, V, sound velocity, v, and attenuation, a, at frequencies between f = 0.5 and f = 15 MHz, in a wide range of temperature (- 150 to + 400°C) and pressure (up to 2 kbars). The results (V,v,a) are translated into a complex modulus, M* = M’ + iM” and analyzed in terms of the thermodynamic state of the material. Typical results for amorphous and semi-crystalline polymers are presented which show that the technique is a probe of the fundamental features of these materials (glass transition, crystallization, melting, molecular structure) which determine processability and end use properties. The method should prove of great interest for quality and process control.
Thermal Wave Characterization of Glass-Bonded Alumina
Authors: Inglehart Lorretta J. , Haber Richard A. , Wachtman John B. 
Published: March 2011

AbstractWe present the results of a study of glass-bonded Al2O3 with controlled composition and particle size using photoacoustic thermal wave nondestructive evaluation. Experimental results are related to particle size, density, porosity, and thermal properties of the materials.
Neutron Diffraction as a Tool for Non-Destructive Evaluation of Ceramics
Authors: Root John H. , Sullivan James D. 
Published: March 2011

AbstractNeutron diffraction is a powerful probe of the properties of condensed matter. In recent years neutron diffraction has been applied to the non-destructive evaluation of mechanical characteristics of engineering components. This paper presents examples of applications to ceramic composites including the measurement of position dependence of residual strain, grain size and minority phase concentration. In addition, an example of volume-averaged crystallographic texture is presented.
Rapid Non-Destructive Testing of Ceramic Multilayer Capacitors by a Resonance Method
Authors: Boser O. , Kellawon P. , Geyer R. 
Published: March 2011

AbstractA rapid non-destructive test method for ceramic multilayer capacitors made from piezoelectric materials such as barium titanate or lead containing materials is described and evaluated. The test method is based on the internal excitation of standing acoustic waves in the capacitors. The standing waves are severely dampened by defects such as delaminations and pores. An undampened resonance is a good indication of a defect free ceramic multilayer capacitor. This finding was used in a nondestructive test set-up to evaluate about 1,000 capacitors. The test set-up has the potential to test over 100,000 capacitors an hour. Through metallographic (cross section) examination a sorting accuracy of 2% false accepts and 8% false rejects was determined for the high speed test set-up.
Nondestructive Characterization of Beryllium Effects on Ni-Cr Dental Alloy Elastic Properties and Microstructure: Ultrasonics, X-Ray Diffractometry, Scanning Electron Microscopy and Wavelength Dispersive Spectrometry
Authors: Singh Surendra , Katz J. Lawrence , Rosenblatt B. S. 
Published: March 2011

AbstractKnowledge of structure-properties relationship is a key factor in the development and improvement of new and existing metal alloys through manipulation in their chemical-compositions. In this study, the elastic properties and microstructure of cast Ni-Cr-Be and Ni-Cr dental alloys were studied. The elastic properties, i.e., Young's, shear and bulk moduli and Poisson's ratios, were determined using measurements on the ultrasonic velocities and densities. Both the shear and the longitudinal (dilatational) velocities were measured using an ultrasonic pulse-through-transmission method; density was measured using a buoyant force method. In microstructure, crystallinity, porosity, particle-size and quantitative elemental compositions were studied using x-ray diffractometry (XRD), scanning electron microscopy (SEM) and wavelength dispersive spectrometry (WDS) respectively. These results show that: (1) the addition of Be increased significantly the alloy's elastic moduli and Poisson's ratio; and (2) the presence of Be in Ni-Cr alloy also significantly modified its microstructure by producing a second binary phase, Ni-Be, in eutectic areas.
X-Ray Determination of Strain Distribution in Inconel Alloy 600 C-Ring
Authors: Lo C. F. , Kamide H. , Feng G. , Mayo W. E. , Weissmann S. 
Published: March 2011

AbstractAn Inconel Alloy 600 C-ring was subjected to various strain levels and the deformation process was monitored by a Computer Aided Rocking Curve Analyzer (CARCA). A large grain population was sampled, and the calibration curve of average rocking curve halfwidth of the individual grains relating to the nominal strain was established. The strain distribution as a function of the angular position along the peripheral surface layer and layers at different depth distance was obtained. Up to C-ring closure at the nominal strain of 3.3% at the apex, the induced plastic strains were confined to a surface layer of 30–40 gm in depth.The largest strain and strain gradients below the surface occurred at the apex and near apex region. The extent and the spread of microdeformation inhomogeneity increased with applied strain. At ring closure some grains exhibited large plastic strains while others exhibited only small plastic strains or were not affected by the deformation process at all. These experimental results were not in agreement with the current theoretical understanding of the deformation of C-ring since these theories did not take shape changes into account. When such changes were included, good agreement on the angular strain dependence for the apex and near apex region were achieved between experiment and theory. It was concluded that the CARCA X-ray method can be a useful research tool in aiding and guiding mathematical modeling of non-linear inelastic behavior of solids by disclosing important microstructural and micromechanical aspects.
Surface Roughness and Correlation Length Determined from X-Ray Diffraction Line Shape Analysis on Germanium (111)
Authors: Shen Q. , Blakely J. M. , Bedzyk M. J. , Finkelstein K. D. 
Published: March 2011

AbstractIn an x-ray diffraction experiment performed on a germanium (111) crystal, both the rod-like and the diffuse-like scattering from the surface have been observed on a nonspecular crystal truncation rod. These scattering contributions can be explained using existing theory on surface roughness. Two treatments to the Ge (111) surface have been used to provide examples with different roughness characteristics for this study. Quantitative analysis results in a surface roughness of 2.5+0.3Å for a clean surface passivated with iodine and 4.3+0.5Å for a Syton polished surface covered with a naturally grown oxide layer. A typical lateral scale of flat surface regions has also been obtained from the transverse width of the diffuse-like scattering peak, and found to be 200 A and 400 Å respectively.
Studies of an InAs/GaAs Heterojunction by Total-Electron-Yield
Authors: Krol A. , Sher C. J. , Storch D. R. , Woronick S. C. , Krebs L. , Kao Y. H. , Chang L. L. 
Published: March 2011

AbstractTotal electron yield (TEY) of an InAs/GaAs heterojunction due to soft x-ray excitation has been studied. This heterojunction was prepared by an overgrowth of a 600 Å InAs layer on a GaAs substrate using molecular beam epitaxy. Experimental data are compared with theoretical analysis based on a modified Fresnel formulation to calculate the wave field distribution in stratified media with interfacial roughness. The TEY angular profiles obtained at a given x-ray energy reveal information on the interfacial roughness, secondary electron escape length, attenuation length of elastically scattered photo-electrons, and optical constants of the epilayer in the xray regime.
Reflectivity of Soft X-Rays by Polymer Mixtures
Authors: Russell T. P. , Jark W. , Comelli G. , Stöhr J. 
Published: March 2011

AbstractThe specular reflectivty of soft x-rays has been used to investigate the surface behavior of mixtures of poly(vinylidene fluoride), PVF2, and poly(methyl methacrylate), PMMA. Mixtures where the concentration of PMMA is 0.8 where investigated as a function of the preparation and annealing conditions. It was found that mixtures prepared by rapidly casting from dimethylformamide, DMF, exhibited a gradient in the concentration of the two components. The gradient extended over large distances and was such that PMMA, the higher surface energy component was located preferentially at the surface. With annealing at 165°C, the width of the gradient diminished but the concentration of PMMA remained high at the surface. Films of the mixtures prepared under a slower solvent evaporation procedure produced a reflectivity profile characteristic of a phase separated mixture. The extent of phase separation was reduced with annealing. In all cases the roughness of the surface of the films was found to be 5.OÅ or less.
X-Ray Diffractometer for the Study of a Monomolecular Film Spread on a Liquid Substrate
Authors: Robinson Karl M. , Mann J. Adin 
Published: March 2011

AbstractThe study of ultrathin films spread on liquid substrates has been limited to macroscopic observations of general film behavior. Synchrotron radiation has provided the means of observing the two-dimensional crystalline properties of monolayers. Our recent experiments performed on NSLS X-23B beam line was the trial run of a new liquid surface diffractometer. Major emphasis has been placed on vibrational and environmental isolation of the film, in addition to 0.1 micron resolution in the control of beam positioning. The film is examined in a closed, ultraclean environment consisting of a fused silica trough, purified N2 atmosphere, 0.1°C temperature control and chromatography grade or better solvents and surfactants. Surface properties (surface tension, and visco-elastic moduli) are monitored by surface laser light scattering spectroscopy. The x-ray scattering pattern from the liquid surface contains the expected specular reflection as well as scattered peaks at small wave numbers. We believe these to be caused by high frequency surface ripple fields.
In Situ X-Ray Scattering of Monolayers Adsorbed at Electrochemical Interfaces.
Authors: Toney Michael F. , Melroy Owen. R 
Published: March 2011

AbstractSurface x-ray scattering has been used to study in-situ the structure of Pb monolayers electrochemically adsorbed on Ag (111) electrodes. Pb forms an incommensurate, hexagonal two-dimensional (2D) solid, which is rotated approximately 4.5° from the substrate symmetry directions and compressed relative to bulk Pb. Between monolayer formation and bulk deposition, the Pb-Pb near neighbor distance decreases linearly with applied potential. Due to the chemical equilibrium between the Pb monolayer and the Pb in solution, the isothermal compressibility of the monolayer can be measured and is in good agreement with that calculated for a 2D non-interacting free electron gas model of the monolayer. It is observed that the intensity of surface diffraction from the Ag substrate (the Ag crystal truncation rod) decreases when the Pb monolayer is adsorbed, although the cause of this is not known.
Synchrotron Photoemission Studies of Surfaces and Overlayers
Authors: Chiang T.-C. 
Published: March 2011

AbstractHigh-resolution core-level photoemission spectroscopy allows the distinction of atoms in different layers and in inequivalent sites by their binding energy shifts. By comparison with model structures and reference samples, the number of atoms in each distinct chemical configuration can be determined. The chemical shifts induced by adsorption can be correlated with the electronegativity difference between the substrate and the adsorbate atoms. These observations provide a quantitative description of the interaction and reaction between adsorbates and surfaces, and important information about the atomic structure and the electronic properties can be deduced. Results from several representative systems including the adsorption of In, Ag, and Sn on Si(100) will be discussed.
The Heteronucleation of and Defect Generation in MBE-Grown InAs Layers
Authors: AI-Jassim M. M. , Goral J. P. , Sheldon P. , Jones K. M. 
Published: March 2011

ABSTRACTEpitaxial InAs layers were grown by molecular beam epitaxy (MBE) on GaAs substrates. The initial stages of nucleation were studied by in situ reflection high energy electron diffraction (RHEED). Cross-sectional TEM examination was used to investigate the morphology of the growing layer, while plan-view examination revealed the generation of misfit dislocations. The growth mode was found to depend mainly on the conditions used to nucleate the epitaxial layer. In most cases, Stranski-Krastanov type of growth was observed.
Strain-Induced Lateral Confinement of Carriers in Semiconductor Quantum Wells
Authors: Kash K. , Bhat R. , Mahoney Derek D. , Worlock J.M. , Lin P.S.D. , Scherer A. , Van Der Gaag B.P. , Koza M. , Grabbe P. 
Published: March 2011

ABSTRACTWe describe here an effort to provide lateral confinement of carriers within a continuous InGaAs quantum well by creating a pattern of strain in the well. A compressed InGaAsP layer overlying the quantum well and the InP barrier was patterned into submicron stressor wires by etching to within approximately 20 nm of the InP barrier. The relaxation of the compression at the edges of the quaternary stressors resulted in dilation of the quantum well material under their centers, thus lowering the band gap of the material, providing confinement for both electrons and holes there. We observed a red shift of the quantum well luminescence of 7 meV for 400 nm wide wires, evidence for the strain-induced lateral confinement. This is the first observation of a red-shifted band gap in submicron strain-confining structures.
Dislocations in GaAs/Si Interfaces
Authors: Zhu Jane G. , McKernan S. , Carter C. B. , Schaff W. J. , Eastman L. F. 
Published: March 2011

ABSTRACTDislocations present at GaAs/Si interfaces have been characterized using transmission electron microscopy in plan-view. The GaAs was grown by molecular-beam epitaxy on Si (001) substrate tilted* towards the [110] direction. The dislocation network at the interface consists primarily of orthogonal edge dislocations with Burgers vectors of a/2[110] and a/2[110]. However, displacements of these dislocation lines at the interface are observed. These displacements can be attributed to the interaction of 60* dislocations with the network of orthogonal edge dislocations. The density of these 60* dislocations along [110] direction is different from that along [110] direction.
Heteroepitaxy of GaAs on Si and Ge by low-Energy ion Beam Deposition Using Alternating Beams
Authors: Haynes T. E. , Zuhr R. A. , Pennycook S. J. 
Published: March 2011

ABSTRACTIn this paper, we demonstrate the growth of heteroepitaxial thin films of GaAs at low temperatures on Si(100) and Ge(100) substrates by direct deposition from controlled, low-energy (30-50 eV), mass-separated beams of 69Ga+ and 75As+ ions. This represents the first use of two fully ionized beams for the growth of compound semiconductor thin films. Mixing of the constituents was accomplished by periodically switching tile analyzing magnet to alternate between deposition of Ga and As at approximately monolayer intervals. Ion channeling and transmission electron microscopy show that GaAs films grown on Ge substrates at 400°C are free of the microtwins and stacking fault defects which emanate from the interface of GaAs similarly grown on Si. Single-crystal GaAs films with ion channeling minimum yields of around 6% have been grown on Ge(100) substrates at temperatures from 520°C down to as low as 320°C.
Material and Device Properties of 3” Diameter GaAs-on-Si with Buried P-type Layers
Authors: Pearton S. J. , Lee K. M. , Haegel N. M. , Huang C.-J. , Nakahara S. , Ren F. , Scarpelli V. , Short K. T. , Vernon S. M. 
Published: March 2011

ABSTRACTTwo problems facing MOCVD grown GaAs-on-Si are firstly, scale up to 3” and greater wafer diameter with acceptably uniform layer thicknesses and electrical and optical properties, and secondly the achievement of adequate device isolation through the use of buffer layers of low doping density (≤1014 cm−3). We have investigated the thickness uniformity and 300K photoluminescence intensity of 3” Ø, MOCVD grown GaAs layers on Si substrates by whole wafer mapping of these parameters, and correlate the variations found with the gas flow direction during deposition of the GaAs. We have overcome the high background doping densities (n =5−20 × 1015 cm2) in the material by a buried Be implant (1−5 × 1012 at 120 keV) followed by 850°C, 3 sec annealing. This provides adequate isolation for MESFETS and we fabricated such devices with gm's of 160-175 mS mm−1 using our standard process. These values are similar to homoepitaxial MESFETS fabricated in the same way.
Low Temperature GaAs Growth on GaAs and Si with Metal-Organic Molecular Beam Epitaxy Assisted by Hydrogen Plasma
Authors: Suemune Ikuo , Kunitsugu Yasuhiro , Tanaka Yoshimitsu , Kan YAsuo , Yamanishi Masamichi 
Published: March 2011

ABSTRACTNew low-temperature cleaning and growth processes are presented using hydrogen plasma. Cleaning of GaAs and Si surfaces are possible above 200°C and 300°C, respectively. Single-domain GaAs thin films are successfully grown on Si at 400°C using metal-organic compounds for both Ga and As. Selective growth of GaAs is demonstrated at 400°C on a Si surface partially covered withSiO2.
Ion Beam Processing of GaAs at Elevated Temperatures
Authors: Williams J. S. , Elliman R. G. , Johnson S. T. , Sengupta D. K. , Zemanski J. M. 
Published: March 2011

ABSTRACTElevated temperature ion bombardment of GaAs has been examined to investigate the nature of residual damage and the interplay between bombardment-induced defect production and dynamic annealing. The nature of disorder is found to depend strongly on ion energy, species, dose, dose rate and substrate temperature. A temperature regime is identified in which dynamic annealing leads both to the efficient formation of band gap traps for carrier removal and to the low temperature crystallization of pre-existing amorphous layers.
Fabrication of GaAs/AlGaAs Quantum Well Lasers with MeV Oxygen Ion Implantation
Authors: Xiong Fulin , Tombrello T. A. , Wang H. , Chen T. R. , Chen H. Z. , Morkoc H. , Yariv A. 
Published: March 2011

ABSTRACTMeV oxygen ion implantation in GaAs/AlGaAs has been shown to provide a simple and very promising technique for quantum well laser fabrication. A l0μm stripe single quantum well (SQW) graded-index separation confinement heterostructure (GRINSCH) laser made in this way has achieved high performance with high quantum differential efficiency, low threshold current and good electrical isolation characteristics. MeV oxygen ion implantation with optimum thermal annealing produces a deep buried electrical isolation layer in n-type GaAs and reduces optical absorption in GaAs/AlGaAs quantum well structures. Ion implantation stimulated compositional disordering as well as implanted oxygen-related deep level traps may be considered as important effects for electrical and optical modification of interfaces in GaAs and AIGaAs.
Activation Uniformity Dependence of Undoped Semi-Insulating GaAs on Post-Implant Annealing Conditions
Authors: Lanzieri C. , Graffitti R. , Cetronio A. 
Published: March 2011

ABSTRACTIn this article we will illustrate how by suitable furnace design, the radial thermal gradients generated on a GaAs substrate during the post-implant annealing cycle can be virtually eliminated, and how such a technique can result in appreciable improvement in on-wafer activation uniformity (standard deviation better than ± 2%), with virtually constant activation efficiency in going from seed to tail end wafer of a given ingot.
Arsine Ambient Rapid Thermal Annealing
Authors: Jackson T.N. , Degelormo J.F. , Pepper G. 
Published: March 2011

ABSTRACTWe have constructed a multiple wafer arsine ambient rapid thermal anneal (RTA) system and have applied it to the fabrication of high-performance refractory-gate self-aligned GaAs MESFETs. This has allowed us to take advantage of some of the features of rapid thermal annealing for these devices (reduced dopant movement and gate-channel interaction) without the difficulties of capped RTA (decapping problems, cap thermal mismatch stress driven dopant movement and gate-channel interaction) or the uncertain As loss characteristics of uncapped or proximity RTA. The anneal system uses a cylindrical furnace with a graphite boat heated by tungsten lamps with a 60 KW maximum power input. This allows heating rates in excess of 100°C/sec for up to four, two-inch wafers per run with a controlled arsine ambient of 0–20 Torr in an inert gas carrier. Closed loop temperature control is accomplished using a 5 μm wavelength optical pyrometer. The system has been designed to collect the As cracked from AsH, in a downstream trap and essentially no As is deposited in the wafer load area.Using arsine ambient RTA to anneal 15 KV 20Si+ self-aligning implants for GaAs MESFETs with MOCVD grown channels (30 nm, 1.7 × 1018/cm3), we have been able to fabricate enhancementmode self-aligned MESFETs with gm/gd > 20 and extrinsic k-factor as large as 765 mS/V-mm for 0.15 μm gate length.