bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solidification Microporosity in Equiaxed Multi-Component Nickel Aluminide
Authors: Cheng C.J. , Sekhar J.A. 
Published: March 2011

ABSTRACTPorosity formation during solidification in equiaxed microstructure of multicomponent nickel aluminide IC396M is examined. Two types of porosities are identified and related to the other scales of microstructure that evolve during solidification. A correlation is established between the relevent processing parameters and the microstructure variables.
Formation of Metastable Disordered Ni3Al by Pulsed Laser Induced Rapid Solidification
Authors: West Jeffrey A. , Manos James T. , Aziz Michael J. 
Published: March 2011

ABSTRACTThin films of Ni3Al formed by co-evaporation onto insulating substrates form a single phase fcc disordered lattice upon rapid solidification following excimer laserinduced melting with an interface velocity of ~4 m/s. Transmission Electron Microscopy (TEM) and x-ray diffraction (XRD) analyses exhibit no superlattice diffraction at room temperature. Resistivity measurements, indicating that the disordered phase has a higher resistivity and much smaller temperature coefficient at room temperature than the stable ordered (L12) phase, permit us to monitor phase changes and ordering on a fast time-scale. Subsequent annealing recovers long-range order, with resistivity measurements indicating that reordering begins just below 300°C.
Cold-Rolling and Subsequent Annealing of Ti-Rich Tial Polysynthetically Twinned (PST) Crystals
Authors: Oh M.H. , Inui H. , Nishitani S.R. , Yamaguchi M. 
Published: March 2011

ABSTRACTPolysynthetically twinned (PST) crystals of Ti-rich TiAl have been grown and specimens cut from these crystals have been rolled at room temperature and subsequently annealed at 900°C and 1000°C. When the shear deformation parallel to the lamellar boundaries occurs during rolling, PST crystals of Ti-rich TiAl can be rolled to about 50% reduction in thickness at room temperature.The recovery in microhardness occurs in two stages; the first stage associated with the decrease in dislocation density and the second stage connected with the annealing-out of deformation induced twins. The recrystallization mode depends on the amount of reduction. Up to 20% reduction, the lamellar structure is preserved even after the full recovery in hardness. When the amount of reduction exceeds 40%, a structure composed of equiaxed grains of TiAl is obtained after recrystallization. A mechanism of recrystallization of cold-rolled PST crystals, which may explain the dependence of recrystallization mode on the amount of reduction, is proposed.
Powder Processing of Fe3Al-Based Iron-Aluminide Alloys
Authors: Sikka V.K. , Baldwin R.H. , Reinshagen J.H. , Knibloe J.R. , Wright R.N. 
Published: March 2011

ABSTRACTThe production, characterization, and consolidation of Fe3Al-based iron-aluminide powders are described. The consolidated powders were fabricated into sheet. The sheet was tensile tested from room temperature to 800°C and creep tested in the temperature range of 450 to 704°C. Mechanical properties were compared for nitrogen and argon atomized powders. Mechanical properties were also compared for argon atomized powders of Fe3Al alloys containing 2 and 5% Cr.
Production of Fe3Al-Based Intermetallic Alloys
Authors: Sikka Vinod K. 
Published: March 2011

ABSTRACTThe melting of Fe3Al-based alloys at the Oak Ridge National Laboratory (ORNL) and commercial vendors is described. The melting processes evaluated include arc melting, air-induction melting (AIM), vacuum-induction melting (VIM), vacuum-arc remelting (VAR), and electroslag remelting (ESR). The quality of the ingots studied are based on internal soundness and the surface finish obtained. The ingots were analyzed for impurity levels observed in the alloys by various melting processes. Recommendations are made for viable processes for commercial melting of these alloys.
Fabrication of Dense Nickel Aluminide Monolithic and Composite Bodies By Combined Self Propagating High Temperature Synthesis and in Situ Containerless Hot Isostatic Pressing
Authors: Concannon Michael , Hodge Edwin S. , Nyce Andrew C. , Turmel Christopher P. 
Published: March 2011

ABSTRACTMonolithic Ni 3Al and composite Ni3Al/ceramic whisker bodies were fabricated by combined Self Propagating High Temperature Synthesis and in situ containerless Hot Isostatic Pressing (SHS/HIP), starting from cold pressed blends of nickel, aluminum, and boron powders, with and without additions of alumina whiskers. The resultant bodies were dense and had good ductility and mechanical strength at room temperature.
Phase Formation and Phase Stability in the Al-Ti Thin Film System
Authors: Parks L.R. , Lilienfeld D.A. , BØRgesen P. , Raj R. 
Published: March 2011

ABSTRACTThis study focuses on the sequential formation of aluminide phases during annealing of titanium and aluminum thin film bilayers. The formation of titanium-rich intermetallic phases at higher annealing temperatures is emphasized. Using Rutherford Backscattering Spectrometry (RBS) analysis, and x-ray diffraction, phases formed as a function of temperature have been identified. The phases Al3Ti through Ti3Al were observed over the temperature range 450–750°C, where reaction with the SiO2 substrate occurred. All phases were present as discreet layers within the samples with several layered phases coexisting at the higher temperatures.
Chloride-Induced Localized Corrosion of Fe3Al-Type Iron Aluminides: Beneficial Effects of Cr And Mo Additions
Authors: Buchanan R. A. , Kim J. G. 
Published: March 2011

ABSTRACTIn this study, an acid-chloride electrolyte at pH = 4 (H2SO4) and containing 200 ppm Cl- was used to define the effects of Cr concentration (0–6 at.%) and Mo additions (0–2 at.%) on the aqueous corrosion behavior of iron aluminides containing 28 at.% Al. For the Fe-28Al composition, cyclic-anodic-polarization testing indicated passivation, but with a relatively low breakdown potential for pitting corrosion, and a protection potential lower than the open-circuit corrosion potential. Cr additions alone proved beneficial by continuously increasing the pitting potential. However, even at the highest Cr level, 6%, the protection potential was still lower than the corrosion potential, indicating that pitting could initiate after an incubation period. Mo additions were found to raise the protection potential, such that at 1 and 2% Mo levels (4 % Cr), it was higher than the corrosion potential, indicating significantly improved resistance to the initiation of localized corrosion. Immersion testing showed that the latter compositions remained passivated with no localized corrosion for a period of four months, at which point the tests were terminated. The overall results indicated that for satisfactory resistance to chlorideinduced localized corrosion, both higher Cr levels (4–6 at.%) and Mo additions (1–2 at.%) are desirable.
Oxidation Behavior of Advanced Intermetallic Compounds
Authors: Mckee Douglas W. , Fleischer Robert L. 
Published: March 2011

ABSTRACTThe oxidation behavior of a number of ordered high melting point intermetallic materials has been studied in flowing air in the temperature range 1000 to 1500°C. The alloys were selected for acceptable toughness and ductility at temperatures above 1000°C. Included were ruthenium aluminides, chromium silicide and compounds of iridium and ruthenium with elements such as titanium, tantalum, nickel, iron, cobalt, silicon, vanadium and rhenium. In general, alloys containing the metals iron, cobalt and nickel, and also titanium and tantalum, oxidized rapidly at 1000°C and above. Oxidation-resistant materials were those capable of forming scales of chromia/silica or alumina. Intermetallic compounds of chromium and ruthenium formed volatile oxides above 1200°C, but binary compounds of these elements with silicon and aluminum were highly oxidation resistant at lower temperatures.
Third Order Optical Nonlinearity of Soluble Polythiophenes
Authors: Okawa Haruki , Wada Tatsuo , Yamada Akira , Sasabe Hiroyuki 
Published: March 2011

ABSTRACTSoluble conjugated polymers, poly (3-alkylthiophene)s were prepared by chemically oxidative polymerization. The polymers had no absorption at wavelengths longer than 600 nm, indicating that the polymers were suitable for waveguide structures. Dispersion of refractive index (real and imaginary parts) was calculated from the reflectance data using the Kramers-Kronig relation. The dispersion agreed with the result obtained by ellipsometry. Third order optical nonlinearity, χ(3)(−3ω; ω, ω, ω), of the polymers was determined by optical third harmonic generation (THG). Enhancement of the χ(3) by three photon absorption was observed when a beam of 1.54 μm was used as a fundamental. Also, light propagation properties were investigated by using slab waveguides of the polymers.
Mobility and the Glass Transition in Mixed Polymer-Diluent Glasses by NMR
Authors: Jones Alan A. , Inglefield Paul T. , Liu Yu , Cauley Bonnie , Roy Ajoy K. , Kambour Roger 
Published: March 2011

AbstractPhosphorous and proton line shape studies of a trioctyl phosphate diluent in polycarbonate and in a fifty-fifty blend of polystyrene with polyphenylene oxide have been performed to monitor diluent dynamics. Both the phosphorous and proton line shapes are superficially bimodal with a narrow, mobile component of the line shape appearing at temperatures well below the thermal glass transition temperatures. Plots of the h.ction of mobile material versus temperature show two step increases separated by a plateau region. This behavior is analyzed in terms of a distribution of activation energies which results in a bimodal description. The bimodal activation energy distribution corresponds to a bimodal correlation time distribution. The more mobile material is identified with diluent molecules in contact with other diluent molecules in a lattice description which assumes a single phase system is assumed with a purely random distribution of diluent and polymer on the lattice.
AntiPlasticization in the Glassy States of Poly(Vinyl Butyral) and Poly(2,6-Dimethyl Phenylene Oxide)
Authors: Parker Anthony A. , Shieh Yang T. , Ritchey William M. 
Published: March 2011

AbstractSolid state NMR and dynamic mechanical analysis (DMA) techniques have been used to study the “antiplasticization” effects of dihexyladipate (DHA) and tricresylphosphate (TCP) on poly(vinyl butyral-co-vinyl alcohol) (PVB) and poly(2,6-dimethyl phenylene oxide) (PPO) respectively. The DHA and TCP diluents decrease the primary viscoelastic transition temperatures (ax processes) along with their apparent activation energies [1,2] However, glassy state mechanical transitions (P processes) are characterized by increased activation energies. Similarly, carbon T1, T1p, and inversion recovery cross polarization (IRCP) experiments generally show that DHA and TCP suppress motion in the MHz, KHz, and near static frequency regimes. These results collectively suggest that the extent of antiplasticization is dependent on both the frequency regime of observation, and the morphology of the polymers.
HgCdTe/CdTe Multiple Quantum Wells: Growth, Stability, and Optical Properties
Authors: Feldman R.D. , Austin R.F. , Cesar C.L. , Islam M.N. , Soccolich C.E. , Kim Y. , Ourmazd A. 
Published: March 2011

ABSTRACTWe have grown HgCdTe/CdTe multiple quantum wells by molecular beam epitaxy which show room temperature photoluminescence and sharp absorption steps at mid-infrared wavelengths. Quantitative chemical mapping, performed by transmission electron microscopy, indicates minimal interdiffusion during growth. Annealing experiments performed at higher temperatures show that the interdiffusion coefficient is a strong function of the depth of the interface below the surface. Absorption spectra have been accurately modeled with a square well/envelope function approach. The films have been used to passively mode lock color center lasers and produce pulses as short as 120 fsec near 2.7 μm.
Heteroepitaxial HgCdTe/CdZnTe/GaAs/Si Materials for Infrared Focal Plane Arrays
Authors: Johnson S.M. , James J.B. , Ahlgren W.L. , Hamilton W.J. , Ray M. , TOMPA G.S. 
Published: March 2011

ABSTRACTThe structural properties of LPE-grown HgCdTe on heteroepitaxial MOCVD-grown CdZnTe/GaAs/Si substrates were evaluated using high-resolution x-ray diffraction techniques and TEM. Large tilts {up to 4°} between CdZnTe layers and GaAs/Si substrates are a general characteristic of this heteroepitaxial system and are are attributed to the interaction of closely spaced misfit dislocations that arrange to form a tilt boundary. Either {112}CdTe or {552}CdTe can be grown on {112}GaAs/Si; the {552} was shown to result from a first-order twinning operation of {112}. Lamnella {111} microtwins in {111}CdZnTe/{100}GaAs/Si substrates, measured by x-ray techniques, are not readily propagated into the LPE-grown HgCdTe layer. The x-ray FWHM of the LPE HgCdTe is typically at least a factor of two lower than that of the Si-based substrate from annealing and due to the increased thickness of the layer; both mechanisms promote dislocation interaction and annihilation. High performance MWIR and LWIR HgCdTe 128×128 hybrid focal plane arrays were fabricated on these Si-based substrates. An array average of ROAj = 17.8 ohmcm2 for a cutoff wavelength of 10.8 μm at 78K was demonstrated.
New Class of the Semiconductor Materials for Infrared Photodetection
Authors: Akimov Boris A. , Brandt Nikolai B. , Chesnokov Sergei N. , Khokhlov Dmitriy R. 
Published: March 2011

ABSTRACTWe Present the new class of infrared Photodetectors based on the lead-tin tellurides doped with group III impurities. The Persistent photoconductivity effect appearing in these materials provides the opportunity of internal signal integration resulting in the considerable increase in signalto- noise ratio. The integration characteristic time may be changed by means of the operating temperature or alloy composition variation. Even if the integration time is higher than the operation time required there exists an opportunity to quench quickly (∼10−5s) the Persistent photoconductivity. In some regime of quenching the effect of giant quantum efficiency stimulation has been observed. Both the bulk crystal and thin film technologies of the Photodetector Production are developed.
HgTe-CdTe Superlaltice and HgCdTe Epilayer Device Structures Grown by Photon-Assisted Molecular Beam Epitaxy
Authors: Myers T.H. , Yanka R.W. , Mohnkern L.M. , Harris K.A. , Dietz D.W. , Dudoff G.K. , Girouard K.M. , Wang S.C.H. 
Published: March 2011

ABSTRACTHgCdTe grown by photon-assisted molecular beam epitaxy is now suitable for use in high performance detector fabrication. These are the preliminary results for infrared detectors which have been fabricated in HgCdTe grown using this technique at GE. The detectors were fabricated using a modified Hg-diffused diode process. In addition, the first high quantum efficiency infrared detectors based on the HgTe-CdTe superlattice material system is presented as an example of the sophisticated structures obtainable with photon-assisted molecular beam epitaxy. The superlattice detectors exhibited quantum efficiencies as large as 66% (at 140K) at the peak wavelength of 4.9μm and an average quantum efficiency over the 3–5μm waveband of 55%.
The Preparation of InAsSb/InSb SLS and InSb Photodiodes by MOCVD
Authors: Biefeld R. M. , Cunningham B. T. , Kurtz S. R. , Wendt J. R. 
Published: March 2011

ABSTRACTInfrared absorption and photoluminescence have been demonstrated for InAs1-xSbx/InSb strained-layer superlattices (SLS's) in the 8-15 μm region for As content less than 20%. This extended infrared activity is due to the type II heterojunction band offset in these SLS's. The preparation of the first MOCVD grown p-n junction diode was achieved by using dimethyltellurium as an n-type dopant. Several factors, such as background doping and dopant profiles affect the performance of this device. InSb diodes have been prepared using tetraethyltin. The resulting current-voltage characteristics are improved over those of diodes grown previously using dimethyltellurium. Doping levels of 8x1015 to 5x1018cm−3 and mobilities of 6.7x104 to 1.1x104 cm2/Vs have been measured for Sn doped InSb. SLS diode structures have been prepared using Sn and Cd as the dopants. Structures prepared with p-type buffer layers are more reproducible.
Semiconductor Devices and Materials for Optical Communication at 2-4 μM Wavelengths Range
Authors: Fuxi Gan , Hailong Wang 
Published: March 2011

ABSTRACTIn this paper we reported most attractive semiconductor materials for optical sources and detectors with wavelength In the range of 2-4 μm, such as GaInAsSb/GaAlAsSb, InAsPSb/InAs heterostructure and PbCdSSe HgCdTe.The Lasers and detectors have been made using these materials. The performance of the devices were discussed.
MBE Growth of GaInAsSb/A1GaAsSb Double Heterostructures for Diode Lasers Emitting Beyond 2 μm
Authors: Eglash S.J. , Choi H.K. , Turner G.W. , Finn M.C. 
Published: March 2011

ABSTRACTMolecular beam epitaxy has been used to grow GaInAsSb/AlGaAsSb double heterostructures, lattice matched to GaSb substrates, for diode laser emission at 2.3 μm. Doublecrystal x-ray diffraction measurements were used to determine alloy lattice constants, and photoluminescence and infrared absorption spectroscopies were used to determine the bandgaps of the GaInAsSb layers. Alloy compositions measured by Auger electron spectroscopy were consistent with measured lattice constants and bandgaps. Diode lasers fabricated from the double heterostructures were operated in the pulsed mode at room temperature with threshold current densities as low as 1.5 kA cm−2, differential quantum efficiencies as high as 50 percent, and output power as high as 900 mW per facet.
Low Temperature p- and n- Type Doping of InSb Grown on GaAs Using Molecular Beam Epitaxy.
Authors: Thompson Phillip E. , Davis John L. , Simons David S. 
Published: March 2011

ABSTRACT30 nm thick layers of Be-doped InSb were grown by MBE, sandwiched between undoped layers of InSb on semi-insulating GaAs substrates. Using secondary ion mass spectroscopy (SIMS), it has been demonstrated that the p-type dopant, Be, undergoes an anomalous migration towards the top surface for substrate growth temperatures in excess of 340°C. A thermal diffusion process can be eliminated as an explanation since there was not an associated diffusion towards the substrate. At a substrate growth temperature of 340°C, the Be-doped layer had backside and frontside doping concentration gradients of 0.067 and 0.147 decade/nm. respectively. A sample grown at 420°C had a comparable backside doping concentration gradient, but the frontside gradient was essentially zero, i. e., uniform doping tothe surface. Electrical activation of the Be dopant, when grown at 340°C, compared to activation in GaAs grown at 580°C. was 38% and 47% for growth rates of 1.0 and 0.5 μm/h. While the Si dopant does not undergo a migration comparable to that of Be, it has been demonstrated that n-type doping of InSb with Si must be done at growth temperatures less than or equal to 340°C to obtain high carrier concentrations. The maximum n-type carrier concentration obtained was 6.2x1018/cm3, for a 0.5 μm/h growth rate at 340°C.
Dry Etching Techniques and Chemistries for III-V Semiconductors
Authors: Pearton S. J. 
Published: March 2011

ABSTRACTDry etching of HI-V materials using both Cl-based (CCl2F2, SiCl4, BCl3, Cl2) and CH4/H2 discharges will be reviewed. The etch rates using chlorine-based mixtures are generally faster than those utilizing CH4/H2, but the latter gives smoother surface morphologies for In-containing compounds. The use of microwave (2.45 GHz) electron cyclotron resonance (ECR) discharges minimizes the depth of lattice disorder resulting from dry etching, relative to conventional RF (13.56 MHz) discharges. Recent results on the systematics of ECR plasma etching of both In- and Ga-based III-V semiconductors using CCl2F2/O2 and CH4/H2 mixtures will be discussed, including the determination of the maximum self-biases allowable which do not induce near-surface damage to the semiconductor. A further key issue is the prevention of changes in the surface stoichiometry of materials such as InP, where the lattice constituents may have considerably different volatilities in the particular discharge.
Organometallic Epitaxy of Extrinsic N-Type HgCdTe Using Trimethylindium
Authors: Taskar N.R. , Parat K.K. , Bhat I.B. , Chandhi S.K. 
Published: March 2011

ABSTRACTIndium doping of mercury cadmium telluride, grown by organometallic epitaxy, has been accomplished using trimethylindium (TMIn) as the dopant source. Layers, grown by the Direct Alloy Growth (DAG) process, exhibited a linear doping vs TMIn partial pressure characteristic over the 5 × 1016 to 3 × 1018 cm−3 range. A maximum doping concentration of 5 × 1018 cm−3 was obtained in these layers.The optical band edge in these layers was observed to move to higher energy with increased doping. It is shown that this is caused by the Burstein-Moss shift of the bandedge with doping, and that the Cd fraction is independent of the doping concentration.
Hg1-xCdxTe: Defect Structure Overview
Authors: Berding M.A. , Sher A. , Chen A.-B. 
Published: March 2011

ABSTRACTNative point defects play an important role in HgCdTe. Here we discuss some of the relevant mass action equations, and use recently calculated defect formation energies to discuss relative defect concentrations. In agreement with experiment, the Hg vacancy is found to be the dominant native defect to accommodate excess tellurium. Preliminary estimates find the Hg antisite and the Hg interstitial to be of comparable densities. Our calculated defect formation energies are also consistent with measured diffusion activation energies, assuming the interstitial and vacancy migration energies are small.
Materials Issues and Device-Degradation in the Ingaas(P)/Inp System
Authors: Ueda O. 
Published: March 2011

ABSTRACTThis paper reviews the current status of material issues in the InGaAs(P)/InP system and our understanding of degradation in InGaAsP/inP double-heterostructure lasers and LED's.Among the materials issues for this system are the generation of defects and the thermal stability of the material. Crystal growth-induced defects can be classified into interface and bulk defects.; the former group includes misfit dislocations and inclusions and the latter structural and non-structural precipitates. Thermal stability can lead to structural imperfections stuch as quasi-periodic modulated structure due to spinodal decomposition of the crystal either at the liquid/solid interface or growth surface, and atomic ordering which also occurs on the growth surface through migration and reconstruction of deposited atoms. Diffusion processes in InP often lead to the generation of microdefects in this material. Finally, in metallization procedures, alloy reactions between the semiconductor and electrode occasionally take place forming non-planar/non-uniform interfaces.Three major degradation modes, rapid degradation, gradual degradation, and catastrophic failure in InGaAsP/InP double-heterostructure lasers and LED's, are discussed. For rapid degradation, recombination-enhanced dislocation climb and glide, which are responsible for degradation, do not occur easily InGaAsP/JnP system. Differences in the ease with which these phenomena occur in InGaAsP/InP and other systems are presented. Based on the results, dominant parameters involved in the phenomena are discussed. Gradual degradation takes place presumably due to recombination enhanced point defect reaction in GaAlAs/GaAs-based optical devices. However, we do not observe this mode in InGaAsP/InP-based optical devices. Catastrophic failure due to catastrophic optical damage at a mirror or at a defect in GaAlAs/GaAs DH lasers, is not found in InGaAsP/lnP DH lasers. Degradation of InGaAsP/InP double-heterostructure LED's with large current application is also presented. These results indicate that InGaAsP/InP optical devices ensure very high reliability in longwavelength communication systems.