bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature Dependence of Damage in Boron-Implanted Silicon
Authors: Ottaviani G. , Nava F. , Tonini R. , Frabboni S. , Cerofolini G. F. , Cantoni P.
Published: March 2011

We have performed a systematic investigation of boron implantation at 30 keV into <100> n-type silicon in the 77 –300 K temperature range and mostly at 9×1015 cm−2 fluence. The analyses have been performed with ion channeling and cross sectional transmission electron microscopy both in as-implanted samples and in samples annealed in vacuum furnace at 500 °C and 850 °C for 30 min. We confirm the impossibility of amorphization at room temperature and the presence of residual damage mainly located at the boron projected range. On the contrary, a continuous amorphous layer can be obtained for implants at 77 K and 193 K; the thickness of the implanted layer is increased by lowering the temperature, at the same time the amorphous-crystalline interface becomes sharper. Sheet resistance measurements performed after isochronal annealing shows an apparent reverse annealing of the dopant only in the sample implanted at 273 K. The striking differences between light and heavy ions observed at room temperature implantation disappears at 77 K and full recovery with no residual damage of the amorphous layer is observed.
In-Situannealing Transmission Electron Microscopy(Tem) Study of the Ti/GaAs Interfacial Reactions
Authors: Kim Ki-Bum , Sinclair Robert
Published: March 2011

In-situ annealing TEM experiments were performed on the Ti/GaAs system in order to study the dynamic behavior of interfacial reactions. Both plan-view and cross-sectional samples were investigated in either diffraction and imaging (both conventional and high resolution) modes. During experiments, we observed the following: (a) At the initial stage of reaction, the TiAs phase formed at the original Ti/GaAs interface with a distinct orientation with respect to the substrate; (b) as the reaction proceeded, the TiAs phase formed in a random manner; (c) finally, the liberated Ga species from the GaAs diffused out to the metal film and formed TiGa2 phase in the plan-view sample similar to the furnace-annealed case. For the cross-sectional sample, however, we did not observe any Ti:Ga phase formation. Instead, we observed the formation of voids both in the Ti film and in the GaAs substrate. The formation of different microstructure between in-situ and furnace annealed cases is explained by the sample geometry during annealing.
Antiphase Defect Reduction Mechanism in Mbe Grown Gaas on Si
Authors: Shiraishi Takashi , Ajisawa Haruhiko , Yokoyama Shin , Kawabe Mitsuo
Published: March 2011

It 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

Photoemission 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

Thin 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

Optical 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

We 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

The 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

Transient 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

Results 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

We 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

During 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

The 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

Photoelectron 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

This 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

We 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

Gap 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

We 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

1H 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

Hydrogenated 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

The 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

We 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

The 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

The 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

Formula 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).
Natural Analogues: Alamosa River Monzonite Intrusive into Tuffaceous and Andesitic Rocks
Authors: Brookins D. G. , Abashian M. S. , Cohen L. H. , Williams A. E. , Wollenberg H. A. , Flesser S.
Published: March 2011

This project encompasses investigations of selected natural analogues of minerals and rocks containing radioelements and fission-product elements, to ascertain how radionuclides and their daughter elements may migrate from sites of origin in response to long-term natural processes such as heating due to an igneous intrusion, circulating hydrothermal systems, diffusion through the rock matrix, weathering and erosion. Comparison of natural occurrences with conceptual models based on laboratory data will furnish a test of such models over time periods comparable to or longer than those expected for a repository.
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

At 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

In 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.
Surface Layer Formation on a Nuclear Waste Glass
Authors: Lutze Werner , Malow GÜnter , Rabe Harald , Headley Thomas J.
Published: March 2011

Surface layers are a common feature of leached surfaces of borosilicate waste glasses. Layers are also observed upon weathering of volcanic glasses[l] and of silicate minerals[2]. The question of whether these layers can protect the glass against further attack by decreasing the leach rate is stïll a subject of controversy[3]. Both in geochemical work[4] and in work on waste forms [5,6], surface layers are attributed a protective function, and the stability of leached, million years old volcanic glasses[1] may be due to the presence of palagonite, a thin (≤100 μm) alteration layer, which forms in a few years but does not seem to increase in thickness after this time. The present study investigates the effects of layer formation on leaching kinetics of a borosilicate waste glass containing 20 wt.% LWR-type simulated waste oxides.
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

238Pu-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

The 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

Concretes, 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.
An Evaluation of Alternative TRU Technologies
Authors: Bida G. , Mackenzie D. R.
Published: March 2011

In support of the responsibility of the Nuclear Regulatory Commission (NRC) to promulgate a regulation for disposal of high level waste in a geologic repository, a technical support program was conducted at Brookhaven National Laboratory (BNL). The principal objectives of the program were (1) to identify and provide an understanding of those factors and processes which affect repository performance, and (2) to provide the information needed to develop and support proposed regulations, criteria, and performance objectives that will ultimately be issued as the final rule for disposal of high level radioactive wastes in geologic repositories, known as 10 CFR 60 [1]. As part of the technical support program in the development of nuclear waste form criteria, three main areas of transuranic (TRU) waste management have been evaluated: immobilization processes and waste forms proposed for ultimate geologic disposal of TRU waste; management of TRU waste by decontamination; and potential problems associated with gas generation by certain TRU wastes [2]. The evaluation results from a review of, primarily, relevant DOE research and development efforts reported up to the end of CY 80. Also, only the definitions, criteria, and performance objectives detailed in the Advance Notice of Proposed Rulemaking (10 CFR 60) [3] were considered in this evaluation. This is important to note since significant differences in the waste package definition and in the statement of performance objectives as well as in other areas exist between the Advance Notice [31 and the Proposed Rule [1].
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

Synroc 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.
Supernatant Treatment Considerations for the Neutralized Waste at West Valley
Authors: Gockley G. B. , Lahoda E. J. , Pope J. M.
Published: March 2011

The neutralized high-level waste, stored at the Western New York Nuclear Service Center in West Valley, New York, was produced during the operation of the Nuclear Fuel Service, Inc. commercial nuclear fuel reprocessing plant. The supernatant is a highly concentrated salt solution (NaNO3 , NaOH, Na2SO4 and NaCl) containing essentially all of the dissolved cesium as the primary radioactive component. The sludge is primarily iron and aluminum hydroxides and contains strontium and the bulk of the long-lived isotopes. The supernatant will be treated to remove essentially all of the radioactivity and then be concentrated and disposed of as low level nuclear waste. The following supernatant treatment considerations have been evaluated on a laboratory scale using simulated West Valley waste: 1) Organic ion exchange resins; 2) Inorganic ion exchange media; 3) In-tank processing. These processes will be described and preliminary laboratory data will be presented.
Corrosion Resistant Canisters for Nuclear Waste Isolation
Authors: Magnani Nicholas J.
Published: March 2011

Corrosion resistant canisters are an important component of the engineered barriers of a nuclear waste disposal system. In addition to providing containment for the waste form during transportation and emplacement, a durable canister can eliminate hydrothermal interactions with the waste form. The selection of a repository site and emplacement technique will affect canister design and could also impact material selection. While there are still many issues to be resolved, there are two different concepts being evaluated to provide durable canisters for waste disposal: (1) canisters fabricated out of extremely corrosion resistant materials such as Ti-base or Ni-base alloys, and (2) canisters fabricated out of less durable materials but designed with a corrosion allowance. Each of these types of canisters could fail to meet the design objectives through a variety of failure processes. The more important of these are discussed.
Investigations of Suitable Metallic Container Materials for Haw Solidification
Authors: Mirschinka Volker , Halaszovich Stefan , Odoj Reinhard , Forch Ursula , Forch Karl
Published: March 2011

The influence of the main alloying elements of six different steels and high temperature resistant alloys for crucibles containing HAW glass on the homogeneity of the waste glass was investigated. The distributions of iron, chromium, nickel, and cobalt were studied by an electron beam microprobe. The results are given and discussed.
Thermal Conductivity of Waste Forms and Geologic Media
Authors: Pohl R. O. , Vandersande J. W.
Published: March 2011

In order to predict the range of thermal conductivities to be expected in waste forms and in geologic media, an understanding of the pertinent phonon scattering processes is required. It has been shown that grain boundaries in polycrystalline media are unimportant at low temperatures relative to lamellae which arise from twinning, exsolution, or foreign inclusions within the grains. The possible role of lamellar structures on the conductivity at high temperatures will be discussed.
Hydrothermal Simulation of Ion Migration in Selected Argillaceous Sediments: Implications For Backfill Design
Authors: Bratton Lisa , Scheetz Barry E. , White William B.
Published: March 2011

Argillaceous rocks, used either as a repository rock or as a backfill material provide a reactive medium with which escaped radionuclides can react. Solutions containing U, Nd Gd, Cs, and Sr were reacted with bulk specimens of two argillites with the objective of determining penetration of heavy metals into the rock, and the reaction products. The two Devonian argillites were chosen to represent a highly reducing rock containing pyrite and carbonaceous material as accessory minerals, and a clean, alumino-silicate rock containing mainly quartz and layer silicates. Cylinders of rock were reacted with solutions at saturated steam pressures and 200°C.

At the end of the runs, both rocks contained reduced uranium in the form of U02.25. The rare earths were associated with the uranium. There was a precipitated coating of uranium-rich material on the outside of the reducing shale and few of the radionuclides had penetrated the interior. Uranium also formed a precipitate within 0.5 mm of the surface of the oxidized shale leaving a depleted zone near the surface. Cesium and strontium did not penetrate the reducing shale but were uniformly distributed throughout the oxidized shale. Chlorite, apatite and pyrite were found to be the most reactive phases in the shales.
γ-Zirconium Phosphate as a Cs-Waste form for Partitioned Wastes
Authors: Komarneni Sridhar , Roy Rustum
Published: March 2011

γ-zirconium phosphate (γ-ZrP), γ-Zr(HPO4)2 2H2O is an extremely selective cesium ion sieve for nuclear waste solutions. Because of its layer structure, the adsorbed Cs can be directly fixed in γ-ZrP by collapsing the layers upon heat treatment. Fixation of 96 and 98% of the adsorbed Cs was achieved by simple heat treatment at 350°C and 600°C respectively. Thus, heat treatment of this γ-ZrP leads to a good radiophase with good leach resistance. Cs sorbed γ-ZrP can also be converted to CsZr2(PO4)3 [;sodium zirconium phosphate (NZP) radiophase] by sintering with ammonium monobasic phosphate and zirconyl nitrate at about 850°C. Thus, γ-ZrP serves as a precursor to CsZr2(PO4)3 radiophase which has comparable leach resistance to other phases under consideration for radio-Cs immobilization.
Diffusion Measurements in Concrete and Compacted Bentonite
Authors: Muurinen A. , Rantanen J. , Ovaskainen R. , Heinonen O.J.
Published: March 2011

A laboratory method for measurement of diffusion of radionuclides inconcretes and compacted bentonite has been developed. In this method a tracer is introduced through one end into the cylindrical sample closed in a tube and preequilibrated with water. After the introduction period of the tracer the tube is sealed hermetically and the concentration profiles of the radionuclides are measured periodically from the outside of the sample using a collimated detector. Diffusivities are calculated from the activity profiles by fitting the theoretical curve with the measured profile. The paper will give diffusion data for Co, Sr and Cs in some concrete products and for Co and Cs in compacted sodium bentonite.
Compatibility Relationships in the U-Fe-O(-H) System at 400°C: The Implications of the Ferric-Ferrous Buffer for the Immobilization of Uranium and Transuranic Elements
Authors: Smith Deane K. , Phelps Freeborn W. , Scheetz Barry E.
Published: March 2011

The current strategy for the immobilization of nuclear wastes is based upon a system of multiply redundant barriers for which geological containment is the final barrier to the migration of radionuclides in the biosphere. The ability of the respository host rock to buffer the oxygen fugacity of the pore waters is a critical concern for the evaluation of the far-field migration of selected elements; notable Tc, U and TRU elements. The buffer capacity of all proposed host rocks, with the exception of salt, is based upon the presence of both ferric and ferrous iron in the host rock phases.

The system U-Fe-O(-H) was selected for study because of its significance on the role of Fe in controlling the oxidation state of the U. It has been established that the Fe2+/Fe3+ couple is the controlling factor in limiting the uranium oxidation to the U4+ state.

The results from this experimental study at 400° C (the maximum worse case temperature for a repository) verified the existence of the compatibility triangles between hematite and UO2.00 and magnetite and between U4O9 and UO2.00 and hematite. These data indicate that in the presence both ferric and ferrous ions, the form of the uranium dioxide is retained as stoichiometric UO2.00 and not as an intermediate member of the UO2+x solid solution series or other higher oxide. These experimental results are in concert with the phase relationships predicted by Freeborn et al. (1980) based upon thermochemical calculations.
Laser Irradiation of InSb:Ge Thin Films
Authors: Rubin K. A. , Ortiz C. , Solis J. , Roche K.
Published: March 2011

The effect of 647nm Kr-ion laser and 514.5 nm Ar-ion irradiation on 1 and 7 μm diameter regions, respectively, of (In43Sb57)87 Ge13 thin alloy films was determined. Laser irradiation times of 50ns - 20μs produce different reflectivity states. An amorphous state of increased reflectivity with respect to the as-deposited amorphous state was produced only with the smaller beam after short pulse (∼100ns to ∼500ns) laser irradiation. Slightly longer pulses caused formation of surface corrugations. The corrugation morphology occurred in the nanosecond regime both in air and vacuum. Further laser annealing caused crystallization and decreased reflectivity. The crystallization microstructures were random cellular for the irradiation in air. Irradiation in vacuum produced three, distinct concentric structures.
Deposition of Dielectric Optical Coatings: A Microstructural Study of the Deposited Layers and Interfaces
Authors: McCarthy J. M. , Thomas L. E. , Pawlewicz W. T. , Frydrych W. S. , Exarhos G. J.
Published: March 2011

Thin dielectric films for optical applications are deposited on substrates using a variety of techniques including reactive sputtering, solgel reaction, and ion assisted plasma deposition. This transmission electron microscopy study characterizes optical coatings produced by the above deposition techniques and shows how changes in deposition conditions change microstructure and as a result the optical properties.
Laser Assisted Photodeposition of Gold on Semiconducting Material
Authors: Joshi N. V. , Quintero P. , Galindo H. , de Joshi Virginia Otero
Published: March 2011

Recently, much interest has been created in laser driven chemical reactions and their application towards photodeposition of thin films of metals on semiconducting substrates. The next logical step is to verify the capability of this technique in making adequate electrical contacts for microelectronic fabrications and for circuit writing. Some work in this direction has been reported for Iron and Tungsten. However, deposition of gold has not been reported so far, even though it is very significant from the technological point of view. Therefore, we are proposing here a method for photodeposition of gold.

this pupose, Pyridine gold (III) trichloride was found to be adequated and it was prepared by a conventional method, then dried under vacuum for 48 hours. A concentrated solution was made by dissolving it in Dimethyl sulfoxide. A tiny drop of it was put on the substrate and exposed to radiation 488 nm, obtained from an argon ion laser. The time of photodeposition depends upon the power of the beam; for 2 watt/mm2 and for four to six minutes of continuous exposure, good, low noise, reliable and nearly ohmic contacts were obtained.

The method is found to be suitable for both conventional and non conventional semiconductors such as ZnTe, doped and undoped ZnSe, and diluted magnetic semiconductors such as Zn1−xMnxSe for which normally used methods are not applicable. The present technique can also be extended to the hiqh Tc superconductor YBa2Cu3O7. The possible mechanism of photodeposition is also discussed.
Optical Waveguides in GaAs/AlGaAs MQW Structures Formed by Silicon Induced Quantum Well Mixing
Authors: Wismayer A. C. , Weiss B. L. , Roberts J. S.
Published: March 2011

Si implantation followed by furnace annealing has been used to produce the mixing of GaAs/AlGaAs multiquantum well (MQW) structures grown by MOVPE. Masked implants have been used to fabricate stripe optical waveguides. Results are presented here for the effect of the ion dose and the annealing time and it is shown that complete mixing occurs for a 1015 cm−2 dose of 500 keV Si+ after annealing at 750 °C for two hours. Waveguides fabricated using this process showed a minimum TE mode propagation loss of 33 dB cm−1 at a wavelength of 1.15 μm.
Microstructural development during Fabrication of Ti:LiNbC3 Optical Waveguides
Authors: McCoy M. A. , Dregia S. A. , Lee W. E. , Sanford N. A.
Published: March 2011

The microstructural development of Ti:LiNbO3 optical waveguides as a function of annealing time and temperature was studied using transmission electron microscopy. The morphological evolution of the deposited Ti film can be characterized by three stages: (i) oxidation beginning at low temperatures, (ii) coarsening and secondary grain growth of the oxide film at higher temperatures and (iii) eventual film breakup and void formation. Secondary grain growth is driven by minimization of interfacial energy of grains which have a special epitaxial relationship with respect to the LiNbO3 substrate.
Single Point Diamond Turning of an Organic Nonlinear Crystal, L-Arginine Phosphate
Authors: Velsko Stephan P. , Syn Chol , Fuchs Baruch A.
Published: March 2011

We have demonstrated that single point diamond turning can be used to generated high optical quality finished surfaces on a new organic nonlinear crystal, L-arginine phosphate (LAP). The proper choice of cutting conditions can produce surfaces with less than 5 angstroms rms surface roughness. Local softening or melting near the cutting tool tip may play a key role in the machining process by ensuring that material is removed by ductile cutting rather than brittle fracture. At the same time, the low melting temperature of LAP makes lubrication and cooling especially important to prevent extensive melting and tool fouling. In spite of the presence of a weak cleavage plane in LAP, the surface quality is relatively insensitive to crystallographic orientation. Tool wear is apparently negligible, so that surface flatness is governed by the stability of the diamond turning machine. Data on residual subsurface strain and preliminary measurements of the optical damage thresholds of diamond turned LAP surfaces will be presented.
Lattice Site for Europium in LiNbO3 by Ion Channeling Experiments
Authors: Rebouta L. , Soares J. C. , Silva M. F. Da , Sanz J. A. , Diéguez E. , Agulló-López F.
Published: March 2011

LiNbO3 is a relevant material to prepare a number of electrooptic (bulk and waveguide) devices. Moreover, its photorefractive (PR) behavior is also potentially useful for optoelectronic applications such as holographic storage and coherent optical amplification. For a full understanding and optimization of the PR effect, the lattice location and valence state of the active impurities is essential, since they determine the ionization and trapping capabilities for free carriers. So far, the information obtained with spectroscopic techniques (EPR, ENDOR, Mossbauer, optical) is not conclusive, except manganese and possible iron.
A Comparative Study of Electron Beam Deposited and Sputtered 7059 Corning Glass Thin Films for Waveguides
Authors: Gupta Mool C.
Published: March 2011

Low optical loss (<dB/cm) thin films of Corning 7059 glass have been prepared by electron beam deposition and by rf magnetron sputtering. The effects of gas pressure, deposition power and oxygen-to-argon ratio on refractive index and optical loss were studied. Deposition rates obtained with the sputtering process were about 0.2 nm/sec while much higher deposition rates (2 nm/sec) were obtained with electron beam deposition. The films were found to be amorphous in structure. The refractive index of electron beam-deposited films was measured as 1.50 while the sputtered film index was measured as 1.525. Film composition and composition profiles determined by RBS, electron microprobe and neutron activation analysis are presented. Sputtered films show uniform elemental composition profiles for Si, Ba, B and Al. Electron beam-deposited films have uniform composition profiles if the deposition power is kept constant. The rms surface roughness of the films, measured using an optical profilometer, is 1 nm. The contributions of surface roughness and cladding layer thickness to optical loss are discussed. The major source of optical loss in sputtered films is light absorption.
Synthesis and Characterization of Diamond-Like Carbon Films using Ion Beam Technique
Authors: Wu Richard L. C.
Published: March 2011

Diamond-like carbon (DLC) coatings have been deposited on several infrared transmitting substrates utilizing the ion beam deposition technique. Optimum deposition parameters have been established as a function of source gas composition, source pressure, ion-impact energy, substrate material and cleaning substrate procedures. Extensive characterization of the DLC films was also performed. Rutherford backscattering and proton recoil techniques were used to analyze carbon and hydrogen content and impurities. These films contain 70% atomic carbon and 30% atomic hydrogen. Transmission electron microscopy was used to analyze the crystallinity, void structure and surface microstructure, which were found to be amorphous and dense. Optical properties, such as refractive index and extinction coefficient, were measured using transmission/reflection spectroscopy, ellipsometry and laser calorimetry. Environmental testing was performed using various acids and solvents. The thermal stability and moisture penetration on these DLC films were extensively investigated. The effect of high ion energy radiation on DLC films was studied. Details of the preparation method and characterization of DLC films are presented.
Effect of Heteroatomic d10 Interactions on the Optical Properties of Cu+ Doped Ag+-ß″-Alumina
Authors: Barrie J. D. , Dunn B. , Stafsudd O. M.
Published: March 2011

The optical properties of Cu+ doped Ag+-ß″-alumina are strongly affected by interactions between the d10 closed shell Cu+ and Ag+ ions. These effects can be distinguished from Cu+-Cu+ interactions previously observed in ß″-alumina, and produce a strong red emission upon ultraviolet excitation.
Characterization of Grain Boundaries and Interfaces by High Resolution Transmission Electron Microscopy
Authors: Krakow William
Published: March 2011

Several examples will be given of high resolution electron microscope images of both grain boundaries and interfaces and the methods which have been applied to understanding their atomic structure. Specific expitaxial interfacial structures considered are: Pd2Si/Si used for ohmic contacts, Al on Si overlayers and CaF2/Si where the CaF2, is an attractive possibility as a dielectric material. For the case of grain boundaries specific examples of both twist and tilt boundaries in Au will be given to show the imaging capability with the new generation of medium voltage electron microscopes.