bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antiphase Defect Reduction Mechanism in Mbe Grown Gaas on Si
Authors: Shiraishi Takashi , Ajisawa Haruhiko , Yokoyama Shin , Kawabe Mitsuo 
Published: March 2011

ABSTRACTIt is shown that antiphase boundary (APB) is annihilated during the growth, by monitoring the surface with reflection high energy electron diffraction (RHEED). The RHEED observation indicates that double domain GaAs changes to single domain within a thickness of 100 nm, while the transition region is estimated to exist within 200 nm from GaAs-Si interface by scanning electron microscope (SEM) observation of etch pits on vicinally polished surface. The self-annihilation mechanism of APB is discussed from these results.
Peotoemission Study of Si (001) Surfaces Exposed to as Flux
Authors: Okumura H. , Miki K. , Sakamoto K. , Sakamoto T. , Misawa S. , Endo K. , Yoshida S. 
Published: March 2011

ABSTRACTPhotoemission spectra (XPS and UPS) of As-covered Si (001) surfaces prepared at high (>600ºC) and low (<450ºC) temperatures and GaAs epilayers subsequently grown on them were measured without exposing to air. It was found that the surface electronic structures of As/Si prepared at the low temperature are different from those of the high temperature sample, the spectra of which can be interpreted as a symmetric dimer model. Differences were also observed between the GaAs epilayers on the As—covered Si surfaces prepared at the high and low temperatures. The temperature dependence of the surface and interface structures are discussed.
Electrical Properties of Thin Intermetallic Platinum-Gallium Films Grown by MBE on Gallium Arsenide and Silicon.
Authors: Sadwick L. P. , Ostrom R. M. , Wu B. J. , Wang K. L. , Williams R. S. 
Published: March 2011

ABSTRACTThin films of the platinum-gallium (Pt-Ga) family have been grown on gallium arsenide (GaAs) and silicon (Si) by molecular beam epitaxy (MBE). A partial list of potential uses for these and similar structures is high temperature stable photodetectors, Schottky andOhmic contacts, epitaxial buried contacts, and field effect transistors. In this work the electrical properties of Pt2Ga, PtGa, and PtGa2 on both GaAs andSi will be presented. The resistivity of these thin films has been found to depend on the crystal quality and phase of the material.
Interface Roughness of Quantum Wells Studied by Time-Resolved Photoluminescence
Authors: Jiang H. X. , Zhou P. , Solin S. A. , Bai G. 
Published: March 2011

ABSTRACTOptical properties of GaAs-Al0 5Ga0 5As multiple quantum wells affected by interface roughness have been investigated by timeresolved photoluminescence. The interface roughness affects on exciton dynamics is shown to be more complicated than those previously well studied line-width broadening of exciton transitions. A two-exponential decay of exciton luminescence and exciton peak shifting with increasing delay time have been observed. These observations have been successfully interpreted in terms of the interface roughness effects.
Epitaxial Growth of Ii-Vi Semiconductors on Vicinal GaAs Surfaces
Authors: Feuillet G. , Cibert J. , Ligeon E. , Gobil Y. , Saminadayar K. , Tatarenko S. 
Published: March 2011

ABSTRACTWe demonstrate that the use of vicinal (001) GaAs surfaces allows twin suppression in M.B.E. grown (111) CdTe. High Resolution Electron Microscopy is used to investigate the atomic structure of and the defects present at the interfaces, as a function of cutting angle and surface preparation. A model is presented that takes into account possible coincidences of facets in CdTe and GaAs in order to explain twin suppression, layer misorientation and the type of interfacial defects.
DX Center in GaAs-GaAlAs Superlattices Suppression and Identification
Authors: Feng S.L. , Bourgoin J.C. , von Bardeleben H.J. , Barbier E. , Hirtz J.P. , Mollot F. 
Published: March 2011

ABSTRACTThe DX center has been studied by Deep Level Transient Spectroscopy in series of GaAs-Ga1-xAlxAs (x = 0.3) and GaAs-AlAs short period superlattices. The existence or not of this center can be understood if its energy level is linked to the L miniband. This suggest a possible way to suppress them by using specific superlattices.
Experimental Confirmation of the Donor-Like Nature of DX in AlGaAs
Authors: Dobson T.W. , Wager J.F. 
Published: March 2011

ABSTRACTTransient decay of persistent photoconductivity (TDPPC) is employed to assess the donor- or acceptor-like nature of the DX defect in AlGaAs. The TDPPC data is analyzed in terms of the non-equilibrium capture kinetics of DX and a variation in the mobility due to ionized impurity scattering as calculated by the Brooks-Herring equation. TDPPC measurements show DX to be donorlike.
Comparison of Pd/Inp and Pd/GaAs Thin-Film Systems for Device Metallization
Authors: Caron-Popowich R. , Washburn J. , Sands T. , Marshall E.D. 
Published: March 2011

ABSTRACTResults of the interaction of 40-nm Pd films on chemically cleaned InP substrates at temperatures from 175 to 650°C are reported. Comparisons are made with previous results from studies of Pd thin-films on GaAs. For both systems, the reaction began upon deposition of the metal. Ternary phases were found after annealing at temperatures up to 250°C. At 450°C and higher, the PdIn or PdGa phase was dominant because of loss of volatile P or As. Possibilities for making ohmic contacts based on these systems are discussed.
A Kinetic Phase Diagram for Ultrathin Film Ni/Si(111): Auger Lineshape Results
Authors: Bennett P. A. , Butler J. R. , Tong X. 
Published: March 2011

ABSTRACTWe have used Auger spectroscopy to monitor chemical reactions during solid phase epitaxy by contact reaction in the Ni/Si(ll1) ultrathin film system. We show that coexisting phases may be separated by numerically fitting the composite Si LVV lineshape using a linear combination of single phase “fingerprint” spectra. Sytematic measurements of coverage and temperature conditions are compiled into a kinetic phase diagram. Comparison with conventional (1000Å) thin film data suggest that the reactions forming Ni2Si and NiSi at > 20 Å thickness are bulk diffusion limited, while surface diffusion dominates at lower coverage. On the other hand, the formation of NiSi2 appears to be nucleation limited at all coverages, with dramatic variations in reaction rate with film thickness. This is discussed in terms of a competition between surface and bulk free energies.
Quaternary Phase Equilibria in the Ti-Si-N-O System: Stability of Metallization Layers and Prediction of Thin Film Reactions
Authors: Bhansali A.S. , Sinclair R. 
Published: March 2011

ABSTRACTDuring high temperature circuit fabrication, metallization layers can come in contact with both solids and gases. Their stability can be addressed with the aid of phase equilibria. Using the Gibbs phase rule as a basis, a method for generating phase diagrams for multicomponent systems can be established. This procedure is described and illustrated by reference to the quaternary phase diagram of Ti-Si-N-O. This phase diagram can then be used to predict stability and/or reactions in metallization layers and thin films.
Explanation of the Anomalously Large Defect-Optical-Absorption Energies in Doped Amorphous Silicon
Authors: Branz Howard M. 
Published: March 2011

ABSTRACTThe longstanding controversy over the anomalously large subgap optical absorption energies in n-type (1.1 eV) and p-type (1.3 eV) hydrogenated amorphous silicon (a-Si:H) is described and resolved. Adler suggested that these large values are incompatible with a positive effective correlation energy of the dangling bond defect and a 1.7 eV bandgap. Kocka proposed that dopant-defect pairing deepens each dangling bond transition energy by about 0.5 eV in doped a-Si:H. I assume no deepening due to pairing, a positive correlation energy of 0.2 eV consistent with the observation of dark electron spin resonance in undoped a-Si:H, and dangling-bond relaxation energies of 0.2 to 0.3 eV which are indicated by previous theoretical and experimental work. The postulate of vertical optical transitions then reduces the anomaly from about 0.9 eV to 0.4 eV. This residual anomaly may be explained by electronic-level deepening in doped a-Si:H caused by disorder-induced potential fluctuations of 0.2 eV half-width.
The Density of States in Undoped and Doped Amorphous Silicon-Germanium Alloys Determined through Photoyield Spectroscopy
Authors: Aljishi S. , Shu Jin , Ley L. 
Published: March 2011

ABSTRACTPhotoelectron yield spectroscopy is used to study the occupied density of states (DOS) in undoped and doped a-Si, Ge:H alloys. We find a shift in the top of the valence band to lower energy as the Ge content is increased. The width of the defect band becomes abruptly narrower when Ge is initially introduced. This change is accompanied by a significant shift in the relative position of the Fermi level towards midgap. The defect peak tracks the valence band throughout the entire composition range. The intrinsic valence band tail in the alloys is found to be an exponential with a characteristic slope of 50 to 60 meV independent of composition. Boron and phosphorous doping affect the DOS of the alloys in a manner similar to that measured in a-Si:H.
Completely Integrated Contact-Type a-Si/a-SiC Heterojunction Image Sensor with Poly-Si TFT Drivers
Authors: Kurihara Hajime , Takeshita Tetsuyoshi , Morozumi Shinji 
Published: March 2011

ABSTRACTThis paper describes the performance of both an 8 dots/mm and a 400 DPI contact-type linear image sensors which integrate poly-Si TFT scanning circuits and a-Si/a-SiC heterojunction photodiodes on the same substrate. Each of these image sensors provides excellent cost and performance for their applications. In particular, the 400 DPI image sensor has achieved a higher scanning speed of 1 msec/line by using the integrated scanning circuits with hydrogenated poly-Si TFTs having high carrier mobility.
Oxygenated and Fluorinated Amorphous Silicon Nitride Films and their Use in Thin Film Transistors
Authors: Bhat P. K. , Ogura H. , Madan A. 
Published: March 2011

ABSTRACTWe present a comparison of the properties of films of amorphous silicon nitride, amorphous silicon oxynitride, and amorphous fluorinated silicon nitride deposited by plasma enhanced chemical vapor deposition. The properties of fluorinated silicon nitride films degrade when exposed to air. TFT devices fabricated with silicon nitride and silicon oxynitride insulators show thteshold voltages ≤3 V and source drain current ON/OFF ratios exceeding 107 for gate voltages smaller than 20 V, whereas TFTs with fluorinated silicon nitride insulators show an inferior performance. We also present ideas on the possible relation between the stress in the insulator film and the reliability of TFTs fabricated using these layers.
Defect Distribution and Defect Kinetics in Undoped and Boron-Doped A-Si:H Investigated by Modulated Photocurrents
Authors: Schumm G. , Bauer G. H. 
Published: March 2011

ABSTRACTGap state profiles in a-Si:H around the Fermi energy have been determined by phase shift analysis of modulated photocurrents. Measurements on different samples in various light-soaked and annealed states show a general strong correlation of the defect structure with the Fermi level position, with a minimum in the DOS at Ef and a peak above Ef. A model of the defect structure involving a peak of D+ states above Ef is outlined that accounts for the observed correlations.
Semi-Transparent Amorphous Silicon Solar Cells
Authors: Schropp R. E. I. , Adachi K. , Imajyo N. , Cueto J. A. Del , Bhat P. K. , Madan A. 
Published: March 2011

ABSTRACTWe report on the development of the first large area semi-transparent amorphous silicon solar modules on pre-shaped compound curved substrates. To date, we have achieved an active area (approximately 1800 cm2) efficiency of about 7%. It is shown that, because of enhanced internal reflection, a metal/dielectric back contact is a good alternative to one consisting of merely a transparent conducting oxide (TCO). The dielectric serves as both a passivating layer and an anti-reflection coating.
Bonded Hydrogen and Trapped H2 in a-Si1−xGex:H Alloys
Authors: Vanderheiden E. J. , Williams G. A. , Taylor P. C. , Finger F. , Fuhs W. 
Published: March 2011

ABSTRACT1H NMR has been employed to study the local environments of bonded hydrogen and trapped molecular hydrogen (H2) in a series of a-Si1−xGex:H alloys. There is a monotonic decrease of bonded hydrogen with increasing x from ≈ 10 at. % at x = 0 (a-Si:H) to ≈ 1 at. % at x = 1 (a-Ge:H). The amplitude of the broad 1H NMR line, which is attributed to clustered bonded hydrogen, decreases continuously across the system. The amplitude of the narrow 1H NMR line, which is attributed to bonded hydrogen essentially randomly distributed in the films, decreases as x increases from 0 to ≈ 0.2. From x = 0.2 to x ≈ 0.6 the amplitude of the narrow 1H NMR line is essentially constant, and for x ≥ 0.6 the amplitude decreases once again. The existence of trapped H2 molecules is inferred indirectly by their influence on the temperature dependence of the spin-lattice relaxation times, T1. Through T1, measurements it is determined that the trapped H2 concentration drops precipitously between x = 0.1 and x = 0.2, but is fairly constant for 0.2 ≤ x ≤ 0.6. For a-Si:H (x = 0) the H2 concentration is ≈ 0.1 at. %, while for x ≥ 0.2 the concentration of H2 is ≤ 0.02 at. %.
Hydrogenated Amorphous Silicon Films Prepared by Mercury Sensitized Photochemical Vapor Deposition
Authors: Kamimura Takaaki , Nozaki Hidetoshi , Sakuma Naoshi , Nakajima Mitsuo , Ito Hiroshi 
Published: March 2011

ABSTRACTHydrogenated amorphous silicon (a-Si:H) films were prepared by mercury photosensitized decomposition of silane using a low-pressure mercury lamp. The deposition rate showed an activation type for substrate temperature (the activation energy: 0.13 eV), because the deposition rate would be determined by the rate of hydrogen elimination from the hydrogen saturated surface. Moreover, the relationship was found between the Si-H2 bond density in a- Si:H films and the gas phase reactions.
Light-Induced Changes in the Subgap Absorption of a-SiC:H
Authors: Bennett M. S. , Wiedeman S. , Rajan K. 
Published: March 2011

ABSTRACTThe changes in the absorption spectra of a-SiC films of varying bandgap were monitored as a function of light-soaking time. It was found that the greatest change in absorption occurred at an energy which was 0.55eV less than the energy of the bandgap. It is demonstrated that this could result from a band of states which remain fixed in energy with respect to one of the band edges as the bandgap changes.
Light-Soaking of a-Si:H,F Films Deposited from SiF4 and H2
Authors: Park H. R. , Liu J. Z. , Maruyama A. , Wagner S. 
Published: March 2011

ABSTRACTWe light-soaked two a-Si:H, F films up to 1,300 hours at a generation rate of 5×1020 cm−3s− 1. The films differ in fluorine content (1 vs. 5 at.%) and in hydrogen content (8 vs. 15 at.%). At each step, we measured the subgap absorption with the constant photocurrent method, the dark- and the photoconductivity. The magnitude and rate of light-induced defect production is similar to that of a-Si:H films.
Charge Collection in a-Si:H Particle Detectors
Authors: Pochet T. , Dubeau J. , Hamel L. A. , Equer B. , Karar A. 
Published: March 2011

ABSTRACTThe signal produced by protons in a-Si:H detectors has been measured. The charge collected from a 5.8 μm p-i-n diode is studied as a function of the reverse bias and the energy deposited in the detector. The charge collection process is discussed. Limits on the pair-creation energy, Ep, are obtained (3.4 eV<Ep< 4.5 eV).
Optical Properties of Semiconducting Amorphous Multilayers Consisting of Disordered Wells and Ordered Barriers
Authors: Nitta S. , Itoh T. , Nonomura S. , Morigaki K. 
Published: March 2011

ABSTRACTThe optical properties of random multilayer films are presented. Very small disorder in the well layer thickness (3 A standard deviation in 20 A) change the optical properties drastically. These optical spectrum are found to be useful to detect the disorder in the multilayers and also are very suitable to investigate the properties of randomness.
Properties of Formula 127 Glass Prepared with Radioactive Zirconia Calcine
Authors: Staples Bruce , Cole Hugh , Pavlica Dan 
Published: March 2011

ABSTRACTFormula 127 glass has been developed to immobilize ICPP zirconia calcine. This glass has been prepared remotely on a laboratory scale basis with radioactive zirconia calcine retrieved after ten years of storage from Bin Set 2. The aqueous leachability of the glass produced was investigated and compared through application of standard leach tests with that of Formula 127 glass prepared with simulated calcine. Solid state properties of the glasses prepared with actual and simulated calcines were also compared through application of electron spectroscopy for chemical analysis (ESCA) and scanning electron microscopy (SEM) with energy dispersive X-ray (EDS).
Geological and Petrological Considerations Relevant to the Disposal of Radioactive Wastes by Hydraulic Fracturing: An Example at the U.S. Department of Energy's Oak Ridge National Laboratory In Situ Composites Prepared by Solidification and Mechanical Techniques
Authors: Stephen Haase C. 
Published: March 2011

ABSTRACTAt Oak Ridge National Laboratory the Pumpkin Valley Shale is used as a host formation for hydraulic fracturing waste disposal. Determination of the relationships between the distribution of different lithologies and porosity-permeability trends within this host formation allows these properties, important to hydraulic fracturing operations, to be related to measurable and mappable geological and petrological parameters. It also permits extrapolation of such patterns to little-studied portions of the Pumpkin Valley Shale. Such knowledge better allows for the satisfactory operation and assessment of the hydraulic fracturing at Oak Ridge National Laboratory.
Megascopic Controls on Radionuclide Transport in Groundwater Flow Systems
Authors: Smith Leslie , Schwartz Franklin W. 
Published: March 2011

ABSTRACTIn this paper we investigate how the geologic structure of a basin influences the reliability with which predictions of radionuclide transport within a depository horizon can be made. Results from a series of stochastic simulations show that, in some cases, transport predictions are sensitive to perturbations in the hydraulic properties of surrounding layers, indicating megascopic effects on a basin-wide scale exert a significant control on transport at the macroscopic scale. Other cases are identified where transport is not sensitive to perturbations in the hydraulic properties of surrounding layers. A key factor in this response is the distribution of the hydraulic gradient in the basin.
Effect of Storage Temperature on Self-Irradiation Damage of 238PU-Substituted Zirconolite
Authors: Clinard F. W. , Peterson D. E. , Rohr D. L. , Roof R. B. , Hobbs L. W. 
Published: March 2011

ABSTRACT238Pu-substituted cubic zirconolite (CaPuTi2 O7) was stored at ambient temperature, 575 K and 875 K until alpha decay doses of 2.4 to 3.6 × 1025/m3 had been accumulated. The ambient temperature material swelled to a saturation value of 5.5 vol%, and the originally crystalline structure was transformed to one with an amorphous matrix and small domains that had retained their crystallinity. At 575 K lesser amounts of swelling (4.1 vol%) and transformation were observed, reflecting concurrent partial recovery. The material held at 875 K remained crystalline, swelled only 0.4 vol%, and exhibited formation of isolated defect clusters.
Modeling of Waste/Near Field Interactions for a Waste Repository in Bedded Salt: The Dynamic Network (DNET) Model
Authors: Cranwell Robert M. 
Published: March 2011

ABSTRACTThe Fuel Cycle Risk Analysis Division of Sandia National Laboratories has been funded by the U.S. Nuclear Regulatory Commission to develop a methodology for use in assessing the long-term risk from the disposal of radioactive wastes in deep geologic formations. As part of this program, the Dynamic Network (DNET) model was developed to investigate waste/near field interactions associated with the disposal of radioactive wastes in bedded salt formations. The model is a quasi-multi-dimensional network model with capabilities for simulating processes such as fluid flow, heat transport, salt dissolution, salt creep, and the effects of thermal expansion and subsidence on the rock units surrounding the repository. The use of DNET has been demonstrated in the analysis of a hypothetical disposal site containing a bedded salt formation as the host medium for the repository [1]. An example of this demonstration analysis is discussed. Furthermore, the outcome of sensitivity analyses performed on the DNET model are presented.
Hydrothermal Interactions of Cement or Mortar with Zeolites or Montmorillonites
Authors: Komarneni Sridhar , roy Della M. 
Published: March 2011

ABSTRACTConcretes, grouts, clays and/or zeolites are candidate borehole, shaft or tunnel plugging materials for any nuclear waste repository. Interactions between these plugging materials may take place under mild hydrothermal conditions during the life of a repository. Class H cement or mortar (PSU/WES mixture) was reacted with one of two montmorillonites, clinoptilolite or mordenite at 100° and 200°C for different periods under a confining pressure of 30 MPa. The solid reaction products were characterized by x-ray powder diffraction and scanning electron microscopy after the hydrothermal treatments. When zeolites were in contact (not intimate mixture) with class H cement, they did not seem to alter but clinoptilolite altered to analcime, and mordenite became poorly crystalline in the presence of mortar (containing NaCl) at both 100° and 200°C. When cement or mortar was intimately mixed with zeolites or montmorillonites and reacted hydrothermally, the reaction resulted in the formation of Al substituted tobermorite (11Å type) in all cases (this type of reaction is expected at the interface) at both 100° and 200°C. The mechanism of tobermorite formation includes the decomposition of zeolites or montmorillonites in the presence of alkaline (pH ≃ 12) cement or mortar and recrystallization to form Al substituted tobermorite. Cesium sorption measurements in 0.01N CaCl2on the reaction products revealed that selective Cs sōrption increased in most cases, even though little or none of the original zeolites and montmorillonites remained in the products. For example, Cs sorption Kd(mL/g) increased from 80 in the untreated mortar + Ca montmorillonite mixture to 1700 in the interaction product which is Al substituted tobermorite. Thus, we discover here that Al substituted tobermorite has good selectivity for Cs.
Synroc Production using a Fluid Bed Calciner
Authors: Jay Ackerman F. , Grens John Z. , Ryerson Frederick J. , Hoenig Clarence L. , Bazan Fernando , Campbell John H. 
Published: March 2011

ABSTRACTSynroc is a titanate-based ceramic developed for immobilization of high-level nuclear reactor wastes in solid form. Fluid bed Synroc production permits slurry drying, calcining and redox to be carried out in a single unit. We present results of studies from two fluid beds; the Idaho Exxon internally-heated unit and the externally-heated unit constructed at Lawrence Livermore National Laboratory (LLNL). Bed operation over a range of temperature, feed rate, fluidizing rate and redox conditions indicate that high density, uniform particle-size Synroc powders are produced which facilitate the densification step and give HUP parts with dense, well-developed phases and good leaching characteristics.