bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Hydrogen in Semiconductors and Related Materials by Cold Neutron Capture Prompt Gamma-Ray Activation Analysis
Authors: Paul Rick L. , Lindstrom Richard M. 
Published: March 2011

AbstractA reliable nondestructive method for measuring trace amounts of hydrogen in semiconductors and related materials has long been needed. Cold neutron capture prompt γ-ray activation analysis (CNPGAA) is a nondestructive, multielement technique which has found application in the measurement of trace amounts of hydrogen. The sample is irradiated by a beam of “cold” neutrons; the presence of hydrogen is confirmed by the detection of a 2223 keV gamma-ray. The technique gives bulk analyses (the neutron and gamma radiation penetrate the sample), the hydrogen peak is free of interferences, and the results are independent of the chemical form of hydrogen present. The instrument is capable of detecting less than 10 mg/kg of hydrogen in many matrices. We have used the technique to measure hydrogen levels in a dielectric film on a silicon wafer, semiconductor grade germanium, and quartz.
Characterization of Reactive Ion Etch Damage in GaAs by Triple Crystal X-Ray Diffraction
Authors: Wang Victor S. , Matyi Richard J. , Nordheden Karen J. 
Published: March 2011

AbstractTriple crystal x-ray diffraction (TCXD) is a non-destructive structural characterization tool capable of the separation and direct observation of the dynamic (perfect crystal) and the kinematic (imperfect crystal) components of the total intensity diffracted by a crystal. Specifically, TCXD can be used to measure the magnitude of the diffuse scattering arising from defects in the crystal structure in the immediate vicinity of a reciprocal lattice point. In this study, the effects of BC13 reactive ion etching (RIE) on the near-surface region of GaAs were investigated by analyzing the changes in the diffuse scattering using both the symmetric 004 reflection as well as the highly asymmetric and more surface sensitive 113 reflection. While the results from the 004 reflections revealed little difference between the unetched and the BC13-etched samples, maps of the diffracted intensity around the 113 reflections showed an unexpected and reproducible decrease in the extent of the diffuse scattering in the transverse direction (perpendicular to the < 113 > direction) as the RIE bias voltage was increased. This decrease suggests that the degree of etch damage induced in the GaAs near-surface region is reduced with increasing bias voltage and ion energy. Additionally, the symmetry and orientation of the kinematic scattering was altered. Possible mechanisms for these results willbe discussed.
New Algorithms for Rapid Full-Wafer Mapping by High Resolution Double Axis X-Ray Diffraction
Authors: Loxley N , Cockerton S , Cooke L M , Gray T , Tanner B K , Bowen D K 
Published: March 2011

AbstractWe describe successful algorithms for rapid alignment of the Bragg planes normal to the incidence plane in a high resolution X-ray diffraction experiment. One is appropriate to the surface symmetric geometry and uses a technique of rotation about the specimen normal.From an experimental study of the rocking curve shape as a function of tilt, we have developed a new algorithm which uses tilting about an axis formed by the intersection of the specimen and incidence planes. This has been shown to be reliable for rapid optimization of the diffraction conditions for wafers cut up to 15° off the (001) plane and for asymmetric reflections. Additionally algorithms are outlined which permit rapid location of the maximum of the Bragg peak and deduction of the mean wafer curvature from the X-ray data
Ultra-Smooth Dry Etching of GaAs Using a Hydrogen Plasma Pretreatment
Authors: Shul R. J. , Choquette Kent D. , Howard A. J. , Rieger D. J. , Dirubio C. A. , Freund R. S. , Wetzel R. C. 
Published: March 2011

AbstractWe have attained extremely smooth etched surfaces on GaAs using a hydrogen plasma pretreatment before etching. The resultant morphology exhibits smooth surfaces since the etching proceeds uniformly through the GaAs without micromasking effects arising from a nonuniform surface oxide. We report the effects of hydrogen plasma treatments before RIE of GaAs in two different reactors using a SiCI4 plasma. Optimization of H2 plasma pretreatments has produced improvements in RMS roughness greater than 1 order of magnitude (22.4 to 1.51 nm).
Reflectance Anisotropy and Spectroscopic Ellipsometry Characterisation of Wet Silicon Wafer Cleaning
Authors: Beechinor J. T. , Kelly P.V. , Crean G.M. 
Published: March 2011

AbstractSilicon surfaces cleaned using standard wet chemical processes used in silicon device fabrication have been characterised by two optical techniques, spectroscopic ellipsometry (SE) and reflectance anisotropy spectrometry (RAS). Standard peroxide-based Si(100) wafer cleans were studied by SE. It is demonstrated that the residual film on the Si surface is critically dependent on both the sequence and type of cleaning steps performed. The sensitivity of RAS performed on-line under an air ambient to HF etched Si(110) and 4° off axis Si(100) surfaces is evaluated in comparison with kinetic SE data.
Process Monitoring for Fabrication of Mercuric Iodide Room Temperature Radiation Detectors
Authors: Van Scyoc J. M. , Schlesinger T. E. , Yao H. , James R. B. , Natarajan M. , Bao X. J. , Iwanczyk J. S. , Patt B. E. , van den Berg L. 
Published: March 2011

AbstractIn the fabrication of mercuric iodide room temperature radiation detectors, as in any semiconductor process, the quality of the final device can be very sensitive to the details of the processing steps. Each processing step can either reduce the intrinsic defects and those extrinsic defects introduced by earlier steps, or it can introduce new defects. In mercuric iodide these defects can act as trapping and recombination centers, thereby degrading immediate device performance or leading to long-term reliability problems. With careful study and monitoring of each step, the process can be modified to improve the end product. In this work we used several techniques to study processing steps and their effects. Photoluminescence spectroscopy and photoionization revealed defects introduced during processing. One critical step is the formation of electrical contacts, as both the material choice and deposition method have an impact. Four point probe sheet resistance methods were used to characterize the loss of material from the contact as it reacted with or moved into the bulk semiconductor. Ellipsometry was used to characterize the intrinsic optical functions of the material, and to study the effects of surface aging on these functions. Results from this work provide suggestions for the modification and monitoring of the detector fabrication process.
Characterization of Electronic Materials by Optical Reflectance Spectroscopy and Digital Signal Processing
Authors: Swart Pieter L. 
Published: March 2011

AbstractIon implantation, diffusion, epitaxy, oxidation and ion exchange are common processing steps which alter the refractive index of dielectric media. These changes can be probed non-destructively by optical methods such as infrared and ultraviolet-visible spectroscopy, and related to material structure. An overview is given of the bilinear transform of reflectance and its use in conjunction with Fourier spectral analysis for thickness and refractive index estimation. Closed-form solutions are presently available for the bilinear transformed reflectance of heteroepitaxial multilayer structures, and for materials containing graded refractive index profiles. Salient features such as positions of interfaces and refractive index steps in multilayer media; depth and width of buried inhomogeneous layers; and width of a transition region between layers of constant refractive index can be determined directly. Under certain restrictive assumptions the bilinear transformed reflectance is shown to be invertible, which allows one to determine the complete refractive index profile. Examples are presented which illustrate the determination of thickness and refractive index of individual layers in multilayered structures. Specific examples include silicon-on-insulator, and Il-V heteroepitaxial structures such as InP/InGaAs/lnP. Analysis of the reflectance of medium to high energy implanted Si or GaAs allows determination of mean damage depth and standard deviation. The invertibility of the bilinear transformed reflectance is illustrated by estimating the refractive index profile of nitrogen implanted silicon.
Phosphorus-Vacancy-Related Deep Levels in Gainp Layers Grown by Molecular Beam Epitaxy
Authors: Huang Z.C. , Wie C.R. , Varriano J.A. , Koch M.W. , Wicks G.W. 
Published: March 2011

AbstractDeep levels in lattice matched Ga0.51In0.49P/GaAs heterostructure have been investigated by thermal-electric effect spectroscopy(TEES) and temperature dependent conductivity measurements. Four samples were grown by molecular beam epitaxy with various phosphorus (P2) beam equivalent pressure(BEP) of 0.125, 0.5, 2, and 4×10−4 Torr. We report for the first time, to our knowledge, an electrical observation of phosphorus vacancy point defects in the GaInP/GaAs material system. The phosphorus vacancies, Vp. behave as an electron trap which is located at EC−0.28±0.02 eV. We have found that this trap dominates the conduction band conduction when T> 220K, and is responsible for the variable-range hopping conduction when T < 220K. Its concentration decreases with the increasing phosphrous BEP. Successive rapid thermal annealing showed that its concentration increases with the increasing annealing temperature. Another electron trap at EC−0.51eV was also observed only in samples with P2 BEP less than 2×10−4 Torr. Its capture cross section is 4.5×10−15 cm 2 as obtained from the illumination time dependent TEES spectra.
Electronic Characterization of Dislocations in Rtcvd Germanium-Silicon/Silicon Grown by Graded Layer Epitaxy
Authors: Grillot P.N. , Ringel S.A. , Watsona G.P. , Fitzgerald E.A. , Xie Y.H. 
Published: March 2011

AbstractCarrier trapping and recombination activity have been studied with DLTS and EBIC in RTCVD grown compositionally graded Ge0.3Si0.7/Si heterostructures. DLTS peak height is found to vary with applied bias, and the bias conditions used indicate that at least one peak is present in the homoepitaxial Si buffer layer and perhaps the substrate as well. Variations in EBIC contrast as a function of reverse bias, and DLTS fill pulse experiments both indicate that the DLTS peaks observed are dislocation related. Moreover, the bias dependent decrease in DLTS peak height is observed to occur at different rates for different peaks, indicating a possible connection between certain DLTS peaks and dislocation orientation or type. Activation energies of one electron trapping center and one hole trapping center add up to roughly the expected bandgap in a relaxed GexSi1−x, alloy with x ≦ 0.3, indicating that the electron and hole trapping centers observed with DLTS may, in fact, be associated with the R-G center observed by EBIC.
Structural Defects in Partially Relaxed InGaAs Layers
Authors: Maigne P. , Baribeau J.-M. , Roth A.P. , Boong C.L. 
Published: March 2011

AbstractThe development of novel optoelectronic devices using thick, defect free, strain free buffer layers mismatched to the substrate requires an understanding of the mechanisms responsible for the relaxation of the elastic strain. Using X-ray diffraction, we have studied the structural properties of partially relaxed InGaAs layers as a function of thickness and substrate misorientation and measured the residual strain. This study shows that strain free layers are difficult to achieve even for thicknesses well above the critical layer thickness. Our measurements also show that the relaxation of the strain induces geometrical effects such as a triclinic distortion of the epilayer unit cell and a tilt with respect to the substrate. These deviations from the ideal structure may seriously degrade the quality of optoelectronic active layers grown on relaxed lnGaAs buffer layers.
Deep Level Characterization of LP-MOCVD Grown Al0.48In0.52As
Authors: Ducroquet F. , Guillot G. , Hong K. , Hong C.H. , Pavlidis D. , Gauneau M. 
Published: March 2011

AbstractDeep levels in unintentionally doped A10. 48In0.52As layers epitaxially grown on InP substrates by low-pressure MOCVD have been investigated as a function of growth temperature (Tg ranging from 570 to 690°C). Two different origins for the residual carrier concentration are deduced depending on Tg: i) low growth temperatures favor the creation of a deep donor located at Ec-(0.13±0.04)eV; ii) At higher Tg, a preferential incorporation of a shallow donor occurs, which can be attributed to silicon by SIMS measurements. The oxygen contamination deduced by SIMS and the electrical characteristics of the AlInAs layers do not appear to be correlated.
Hydrogen Passivation Effects in Heteroepitaxial InSb Grown on GaAs by Lpmocvd
Authors: Yoo Byueng-Su , Kim Sang-Gi , Lee El-Hang 
Published: March 2011

AbstractThe effects of hydrogen plasma exposure upon electron Hall mobilities in InSb heteroepitaxial film grown on GaAs substrate have been investigated. After exposure to a hydrogen plasma at 250°C, the electron Hall mobility is significantly increased at low temperatures and the temperature dependence of the mobility is reduced. For the film with a broad x-ray rocking-curve width, 4 h-hydrogen plasma exposure can give rise to the enhancement of the mobility up to 6 times at low temperature. The mobility for the film with a narrow line width is enhanced around 1.5 times. These enhanced mobilities are nearly restored by 350°C rapid thermal annealing. The enhancement of the mobility due to hydrogenation is attributed to the satisfaction of the dangling bonds generated by the misfit dislocations.
Deep Levels in Type-II Superlattices
Authors: Dow John D. , Shen Jun , Ren Shang Yuan , Packard William E. 
Published: March 2011

AbstractQuantum confinement in superlattices affects shallow levels and band edges considerably (length scale of order 100 Å), but not deep levels (length scale of order 5 Å). Thus by band-gap engineering, one can move a band edge through a deep level, causing the defect responsible for the level to change its doping character. For example, the cation-on-anion-site defect in AlxGa1−xSb alloys is predicted to change from a shallow acceptor to a deep acceptor-like trap as the valence band edge passes through its T2 deep level with increasing At alloy content x. In a, Type-II superlattice, such as InAs/AlxGa1−xSb for x>0.2, where the conduction band minimum of the InAs should lie energetically below the antisite defect's T2 level in bulk AlxGa1−xSb, the electrons normally trapped in this deep level (when the defect is neutral) remotely dope the InAs n-type in the superlattice, leaving the defect positively charged. Thus a native defect that is thought of as an acceptor can actually be a donor and control the n-type doping of InAs quantum wells. The physics of such deep levels in superlattices and in quantum wells is summarized, and related to high-speed devices.
Pressure Ratio (PAs/PGa) Dependence on Low Temperature GaAs Buffer Layers Grown by MBE
Authors: Lagadas M. , Hatzopoulos Z. , Calamiotou M. , Kayiambaki M. , Christou A. 
Published: March 2011

AbstractWe have investigated the influence of the pressure ratio (PAs4/PGa) on the structural and electrical properties of GaAs layers grown at 250°C by MBE. SEM photographs have revealed smooth surfaces for PAs4/PGa≥15 and Double crystal X-ray rocking curves have shown an increase on the lattice mismatch δaI/a of the L.T. grown layers and high crystalline quality. Resistivity has not been affected by the different values of PAs4/PGa. n-GaAs epilayers grown on top of L.T. buffer layers have their mobility decreased and the electron trap density increased as revealed by Hall and DLTS measurements.
Effects of Impurities on the Optical Properties of Quantum Dots, Wires, and Multiple Wells
Authors: Bryant Garneit W. 
Published: March 2011

AbstractIdentifying and understanding the effects of impurities and defects in quantum dots, wires, and multiple wells is important for the development of nanostructures with good optical properties. Simple model calculations are presented to show when and how shallow impurities affect the radiative recombination of confined electron-hole pairs. Results for nanostructures are compared with results for bulk systems. Qualitative differences between bulk and confined systems are described.
Optical Investigation of Strained-Layer GaInAs/GaInAsP Heterostructures
Authors: Queisser I. , HÄrle V. , DÖrnen A. , Scholz F. 
Published: March 2011

AbstractWe performed low temperature photocurrent and photoluminescence excitation spectroscopy on tensile and compressively strained GaxIn1-xAs/GaInAsP quantum well layers to determine the band offset of the heterojunction (0.3 <XGa < 0.7). The ratio of the conduction band discontinuity to the heavy hole discontinuity has been obtained from well to barrier transitions and is found to be about 35/65 for gallium contents between 0.4 and 0.6. We obtained the effective heavy hole mass by comparison of PLE transition energies with calculations of the subband levels. We observe that the effective heavy hole mass increases with the gallium content from 0.3 m0 for XGa = 0.31 to about 0.45m0 for XGa = 0.55.
Magnetooptical Studies of Acceptors Confined in GaAs/AIGaAs Quantum Wells
Authors: Holtz P.O. , Zhao Q.X. , Monemar B. , Pasquarello A. , Sundaram M. , Merz J.L. , Gossard A.C. 
Published: March 2011

AbstractMagnetooptical studies have been performed on the shallow Be acceptor confined in the central region of narrow GaAs/AlGaAs quantum wells (QWs) with the magnetic field along the growth direction. The magnetic field dependence of the acceptor transition between the 1S(Г6) hh-like ground state and the excited hh-like 2S(Г6) state has been investigated by means of two independent techniques: Two-hole transitions of the acceptor bound exciton (BE) and resonant Raman scattering. The 1S(Г6) – 2S(Г6) transition energy as a function of the magnetic field has been measured for central acceptors in QWs of widths in the range 50 – 150 Å. The energy levels for the 1S ground states and 2S excited states of the confined acceptor with a magnetic field as a perturbation have also been calculated. These calculations predict a larger splitting between the mj=+3/2 and mj=−3/2 components of the acceptor 1S(Г6) ground state in comparison with the corresponding splitting of the excited 2S(Г6) state. The experimental results are in good agreement with the theoretical predictions derived without any fitting parameters. Furthermore, the Zeeman splitting of the acceptor BE emission has been measured and it is concluded that the J = 5/2 BE state is lowest in energy, similar to shallow acceptor BEs in bulk GaAs.
Hot Filament Assisted CVD of Titanium Nitride Films
Authors: Deshpande Sadanand V. , Gulari Erdogan 
Published: March 2011

AbstractTitanium nitride thin films have been deposited using a novel Hot Filament Chemical Vapor Deposition (HFCVD) technique. In this technique, a resistively heated tungsten wire (∼1700°C) is used to decompose ammonia to obtain highly reactive nitrogen precursor species. This approach allows for low temperature deposition of nitride thin films. In the past, we have used this method to deposit good quality silicon and aluminum nitride films. Titanium nitride thin films have been deposited on Si(100) at substrate temperatures from 500°C to 600°C. These films were characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction, Rutherford backscattering spectroscopy (RBS) and scanning electron microscopy. The effects of deposition pressure, substrate temperature and titanium chloride flow rate on film properties have been studied. TiN films with resistivities as low as 80.0 μΩ-cm have been deposited. RBS analysis indicates that the films serve as excellent diffusion barriers for copper and aluminum metallization on silicon.
The Development of CVR Coatings for PBR Fuels
Authors: Barletta Robert. E. , Vanier P. E. , Dowell M. B. , Lennartz J. A. 
Published: March 2011

AbstractParticle bed reactors (PBRs) are being developed for both space power and propulsion applications. These reactors operate with exhaust gas temperatures in the range of 2500 to 3000 K and fuel temperatures which may be hundreds of degrees higher. One fuel design for these reactors consists of uranium carbide encapsulated in either carbon or graphite. This fuel kernel must be protected from the coolant gas, usually H2, both to prevent attack of the kernel and to limit fission product release. Refractory carbide coatings have been proposed for this purpose. The typical coating process used for this is a chemical vapor deposition. Testing of other components have indicated the superiority of refractory carbide coatings applied using a chemical vapor reaction (CVR) process, however technology to apply these coatings to large numbers of fuel particles with diameters on the order of 500 gim were not readily available.A process to deposit these CVR coatings on surrogate fuel consisting of graphite particles is described. Several types of coatings have been applied to the graphite substrate. These include NbC in various thicknesses and a bilayer coating consisting of NbC and TaC with a intermediate layer of pyrolytic graphite. These coated particles have been characterized prior to test and the results of this characterization will be presented.
New Chemical Approaches to Synthesize Titanium Disulfide
Authors: Sriram Mandyam A. , Kumta Prashant N. 
Published: March 2011

AbstractThe synthesis of oxides by the use of metal alkoxides is well known in the sol-gel process. However, little is known regarding the use of alkoxides as starting materials for nonoxides. In this work titanium isopropoxide has been reacted with different sulfidizing agents to form alkoxy sulfide precursors. In all the processes the transformation of the precursors to form TiS2 has been studied and the morphologies of the sulfide powders have also been compared. Gas chromatography and infrared spectroscopy have been used to study the molecular processes that occur in one of the reactions.
Properties and Potential Areas of Application
Authors: Rempel Andrei A. , Gusev Alexander I. , Berger Lutz-M. , Richter Volkmar 
Published: March 2011

AbstractIn this paper the differences of properties of stoichiometric and nonstoichiometric IVBand VB-Group carbides will be discussed. On the base of newer investigations of their physical and chemical properties it seems to be possible to improve material properties by using them instead of stoichiometric ones in some applications.
Thermal Decomposition of a Copolymer of Methylcyclosiloxanes and Methylcyclosilazanes to Non-Oxide Ceramics
Authors: Yu Ga-Er , Finch Dudley , Edirisinghe Mohan , Parrick John , Ralph Brian , Clarkc David 
Published: March 2011

AbstractA copolymer prepared using methylcyclosiloxanes and methylcyclosilazanes has been pyrolysed in N2 and a NH3/N2 mixture. Thermogravimetric analysis (TGA) in both atmospheres and thermogravimetry-Fourier transform infrared (TG-FTIR) studies in N2 are discussed. The latter results have been used to suggest a mechanism for the thermal decomposition of the copolymer.