bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Water Chemistry on the Leach Resistance of Synroc C
Authors: Woolfrey J. L. , Levins D. M. 
Published: March 2011

ABSTRACTThe chemical durability of SYNROC C has been measured as a function of repository conditions, namely, temperature, surface/volume ratio, groundwater pH and composition. The leach rate of SYNROC C is less dependent on temperature than borosilicate glasses; activation energies range from 15-25 kJ mol-1 compared to 33-74 kJ mol-1 for glass. The rate of release from SYNROC C is very low and independent of solution composition for the solutions studied. There is little variation in leach rate over the pH range 4-9, but at pH 2 the rate is up to 10 times higher. SYNROC C leach rate is independent of flow rate or surface/volume ratio for the mobile waste elements because of the unimportance of solution saturation effects owing to the low concentration of dissolved solids. The differential leach rate decreases rapidly with time because, after initial leaching from grain boundaries and metastable minor phases, the highly insoluble matrix protects the more leachable elements from further attack.
Static Leaching of Radioactive Glass Under Conditions Simulating a Granitic Repository for High-Level Waste: Phase 1.
Authors: Hermansson Hans-Peter , Christensen Hilbert , Clark David E , Björner Inga-Kari , Yokoyama Hayaichi , Werme Lars 
Published: March 2011

ABSTRACTA joint research project with participation from
Japan, Switzerland and Sweden is underway at Studsvik (The JSS-project). The project concerns investigations on the leaching of fully radioactive glass (containing 12 wt% fission product oxides and actinide oxides) manufactured by CEA/Marcoule.So far the glass has been leached in doubly distilled water and in silicate water at 90°C. Some leaching experiments involved the presence of crushed Stripa granite in the same containers as the glass.Due to strong radiation and the presence of plutonium the leaching was carried out in a specially designed lead cave using gilded stainless steel containers.Weight losses, pH and elemental mass losses were determined together with infrared reflection spectral changes. These data are compared to those obtained from a simulated nonradioactive glass of nearly the same composition and to similar alkali borosilicate glasses previously investigated at Studsvik.
The Role of Eh in Nuclear Waste Form Dissolution
Authors: Phelps Freeborn W. , White William B. 
Published: March 2011

ABSTRACTA series of experiments was conducted to evaluate the significance of redox potential, Eh, as an independent opensystem variable in the dissolution of nuclear waste glasses and ceramics. The standard platinum electrode can be used in leach solutions. Measurements on couples with rapid kinetics such as Fe+++/Fe++ give results in agreement with thermodynamic calculations. Highly reducing leaching solutions can be obtained by passing hydrogen through the solvent in the presence of a palladium catalyst.
The Retention of Redox Sensitive Waste Elements in Compacted Bentonite
Authors: Torstenfelt B. , Allard B. 
Published: March 2011

ABSTRACTThe diffusion of technetium, iodine, uranium and neptunium in compacted bentonite has been studied. The possible reduction of the transport rate of these elements (i.e. redoxsensitive elements) by mixing the clay with metallic iron (for technetium, uranium and neptunium) or by adding a chemisorbent (for iodine) to the clay is reported. Technetium has an apparent diffusivity about 5 times higher in the heptavalent state (TcO4−) than in the tetravalent state (TcO(OH)2 or TcO2), uranium and neptunium in their higher oxidation state (VI and V) have apparent diffusivities about 6 and 50 times higher, respectively, than in the tetravalent state. Iodine, as I− (or 103−), has a transport rate more than one order of magnitude lower than TcO4−.
Geohydrologic Factors and Current Concepts Relevant to Characterization of a Potential Nuclear Waste Repository Site in Columbia River Basalt, Hanford Stte, Washington
Authors: Gephart R.E. , Price S.M. , Jackson R.L. , Myers C.W. 
Published: March 2011

ABSTRACTGeologic features are identified that may affect groundwater movement near a repository located in the Columbia River basalt beneath the Hanford Site, Washington State. These include pathways through flow interiors, flow contacts, and bedrock structural discontinuities. Four concepts are considered to describe groundwater movement in basalt. Differences between concepts principally focus on the degree of vertical leakage through basalt flow interiors. The existing geohydrologic data base is preliminary and insufficient to conclusively support one groundwater-flow concept over another. However, it is proposed that available data tend to support the existence of distinct groundwater-flow systems having relatively low vertical leakage under low hydraulic-head gradients except where structural discontinuities are present. A number of geohydrologic characterization activities are underway to reduce the Present uncertainty regarding potential groundwater pathways.
Studies of Altered Vitrophyre for the Prediction of Nuclear waste Repository-Induced Thermal Alteration at Yucca Mountain, Nevada
Authors: Levy Schon S. 
Published: March 2011

ABSTRACTNuclear waste emplacement in devitrified volcanic tuff at Yucca Mountain will raise the temperature of surrounding rock for a geologically significant period of time. This study evaluates the susceptibility of an underlying 50 ft-thick vitrophyre to thermal alteration by examining alteration that occurred in the rock as it cooled after deposition. A 10°C temperature rise should have no mineralogical effects on the vitrophyre, but an increase of 60° or more is likely to result in alteration. Expected mineralogic changes in the vitrophyre caused by this amount of thermal loading include crystallization of zeolites and smectite. Alteration will be concentrated in a thin interval near the top of the vitrophyre and along fractures. Adsorbed water and water in preexisting hydrous minerals and in glass may contribute to hydrothermal alteration of underlying vitrophyre. Bulk porosity change would be slight and local porosity increase would probably be restricted to the upper part of the vitrophyre. Although some fracture filling could occur, such a minor sealing effect would be balanced by development of secondary porosity. Zeolites and smectite, newly-crystallized along fluid flow paths below the waste repository, could provide an enhanced sorptive barrier to radionuclide migration.
Description of the Scope (Simplified Codes For Performance Evaluation) System for Use In Exploratory Analysis of Radionuclide Transporr in a Geologic Medium
Authors: Petrie Gregg M. , Sneider Steven C. , Craig Richard A. 
Published: March 2011

ABSTRACTA tool has been developed to assist investigators in exploring common problems found in radionuclide transport work. This tool consists of an integrated series of programs known as the Simplified Codes for Performance Evaluation (SCOPE) system. The heart of the system is a set of programs which make use of analytical solutions to the onedimensional solute transport for up to three-member decay chains. Longer chains are approximated by combining the results of the one-, two-, and three-member chain solutions with the effects of short lived members.SCOPE also provides programs that allow the user to evaluate the results by integrated radionuclide releases or by dose-to-man. In the first case, the integrated release passing through the boundary of an aquifer over time is compared to a given set of criteria. The criteria normally used are those developed by EPA (Radiation Protection Program 1982) [1] for estimating hazard. To provide the user with the option of calculating dose-to-man, two existing programs (ALLDOS and PABLM) were integrated into the system.The system is not intended to solve all classes of radionuclide transport problems. However, it can provide the user with a good “first cut” understanding of many geohydrologic systems by allowing the problem to be looked at first as one-dimensional flow in a homogeneous geology.
Characteristics of Polycrystalline Copper Films Made by CVD from Cu(HFA)2
Authors: Kim Do-Heyoung , Wentorf Robert H. , Gill William N. 
Published: March 2011

ABSTRACTThin Copper films have been deposited on various substrates by the reduction of copper bis-hexafluoroacetylacetonate, Cu(HFA)2, with hydrogen to investigate the characteristics of the films made at 2–10 torr of total pressure, substrate temperatures of 280–400 °C and precursor temperatures of 55–90 °C. Under the conditions investigated, the highest growth rate was 650 Å/min. and the resistivity of the films was routinely near 2.0 μΩ-cm at 5000 Å or more thickness. Film growth rate depended on precursor concentration and substrate temperature. RBS and AES analysis indicate that the copper deposited at 310–400°C is highly pure. SEM photographs revealed that different structures form depending on substrate kind, the deposition conditions and the deposition time. The surface roughness of the films increased with increasing thickness. The reflectivity of the copper films depends on their thickness and decreases as the grain size increases. The grain sizes in the films were about 0.1–2.0 μm and are correlated with film thickness.
The Effect of Polysilicon Doping (Using Ion Implantation or PBr3 Diffusion or Insitu Doping) on TiSi2 Formation
Authors: Chittipeddi S. , Dziuba C. M. , Kelly M. J. , Kannan V. C. , Irwin R. B. , Kahora P. M. , Cochran W. T. 
Published: March 2011

ABSTRACTIn this work we have studied the effect of polysilicon doping on titanium disilicide (TiSi2) formation using extensive physical and electrical characterization.
Quantification and Characterization of the Thermal Degradation of TiSi2 Using Thermal Wave Analysis
Authors: Fernandes M. G. , Sitaram A. R. , Kottke M. L. , Kaushik V. S. , Pintchovski F. S. 
Published: March 2011

ABSTRACTThermal wave imaging can be used as a rapid non-destructive in-line probe to monitor defects in metals. In the study of the Ti-polysilicon system, this technique has been used to quantify the degradation of the suicide film by monitoring the formation of a second phase during BPSG annealing. The amount of second phase formed was found to vary with Ti preclean, dopant concentration and temperature of BPSG anneal on both blanket and patterned wafers. The second phase has been identified using TEM and AES to be a silicon rich phase. Digitized thermal wave images were used to obtain information regarding the size distribution of precipitates. These distributions have been correlated with resistivity changes in submicron suicide lines.
A Novel Model for Solid State Reactions in Metal-Silicon Diffusion Couples
Authors: Zhang Lin , Ivey Douglas G. 
Published: March 2011

ABSTRACTIn this study, a novel model has been proposed to describe reactions in thin metal film/silicon diffusion couples. A reactive interface in a metal-Si diffusion couple is considered to be a reaction region, and a reaction process in this region is divided into three steps. Several physical quantities have been defined to describe each of these steps, i.e., the diffusion flux of moving reactant to the reaction region, J; the release rate of nonmoving reactant, r, and the formation rate of the growing phase, F. The relationship between these quantities is demonstrated by means of a reaction process plot, which is also developed in this study. A semiquantitative calculation of the reaction process plot has been done for Mn-Si and Ti-Si systems. The results show that the plots can be successfully used to predict suicide formation sequences.
The Use of Tem and Raman Spectroscopy to Determine the Absorption Coefficient and Silicidation Sequence of Cobalt Silicide
Authors: Weaver Louise , Simard-Normandin Martine , Naem Abdalla , Clark Alison 
Published: March 2011

ABSTRACTIn-line thickness monitoring of CoSi2 films is usually carried out by four-point probe resistivity measurements on blanket samples. This method, however, reveals no information about the thickness variation and stoichiometry of the CoSi2 films. Transmission Electron Microscopy (TEM) can provide this information but the technique is destructive, whereas Raman spectroscopy is non-invasive and offers a technique for patterned wafers compatible with current VLSI technology.The CoSi and Co2Si phases exhibit very characteristic Raman signatures which, with glancing angle X-ray diffraction (GA-XRD), can be used to investigate the silicidation sequence. Although CoSi2 does not produce a Raman spectrum, the silicon local mode can be easily detected through the film and is very sensitive to variations in thickness. The intensity of the silicon local mode was measured on a series of ten samples of CoSi, on silicon and the precise CoSi, film thickness subsequently determined by cross sectional TEM. From these measurements, the absorption coefficient of CoSi2 at 500nm was determined.
Interactions Between Metallization or Diffusion Layers and Doped Silicon Plugs in Deep-Submicron Contact-Holes
Authors: Drynan John M. , Hada Hiromitsu , Kunio Takemitsu 
Published: March 2011

ABSTRACTPhosphorus-doped polycrystalline silicon used to plug the high-aspect-ratio, deep-submicron contact-holes connecting suicide metallization layers and substrate diffusion or silicide/polycide layers used in prototype 64 and 256 mega-bit DRAM devices acts as a dopant source at the silicidc/plug and plug/substrate interfaces during thermal processing. This outdiffusion of phosphorus from the contact-hole plug can lead to increased contact resistance which degrades device reliability and performance. Non-doped silicon, titanium, and titanium nitride films have been investigated as phosphorus outdiffusion buffer or barrier layers which reduce or prevent interaction between the doped contact-hole plug and surrounding conduction layers. Non-doped silicon diffusion buffer layers alternately deposited with in situ-doped silicon dopant source layers have been found to be effective in reducing outdiffusion into the substrate whereas a TiN diffusion barrier layer sputter deposited between the plug and WSix metallization prevents dopant outdiffusion into the WSix layer.
A New Approach to Temperature Dependent Ideality Factors in Schottky Contacts
Authors: Horváth Zs. J. 
Published: March 2011

ABSTRACTSchottky diodes often exhibit anomalous current-vol tage characteristics at low temperatures (T) with T dependent ideality factors (IF) and apparent barrier heights (BH) evaluated for the thermionic emission. In this paper theoretical expressions are first presented for the T dependences of the IF and the apparent BH for the thermionic-field emission (TFE) including the bias dependence of BH. Model calculations are reported, which has been performed using these expressions, and their results are compared with the available experimental data. It is shown that the T dependence of the 1 Fs and apparent BHs often may be explained self consistently by the TFE with anomalously high characteristic energies Eoo.
Characterization of Rapid Thermally Nitrided Titanium Films Contacting Silicided and Non-Silicided Junctions
Authors: Chittipeddi S. , Kelly M. J. , Dziuba C. M. , Irwin R. B. , Kahora P. M. , Kaiman V. C. , Cochran W. T. 
Published: March 2011

ABSTRACTIn the present work we have studied rapid thermally nitrided titanium films which contact self-aligned silicided titanium disilicide (TiSi2-salicided) and non-silicided junctions. We correlate electrical contact resistance data to SIMS results.
Oxidation of Semiconducting Iron Disilicide (β-FeSi2)
Authors: Lundberg Nils , Erlesand U. , Östling M. 
Published: March 2011

ABSTRACTIron disilicide (β-FeSi2) has gained significant importance in recent years because of its semiconducting properties. The bandgap is reported to be direct with an energy of 0.85–0.89 eV, thus making the suicide a potential candidate for optical communications and detector applications. Compatibility with standard VLSI processing might involve a suicide thermal oxidation step. This work concerns the kinetics of both dry and wet oxidations of β-FeSi2. The oxide quality was characterized with respect to the electrical breakdown voltage. The results indicate an oxidation temperature dependence of the oxide quality and that dry oxidation yield higher breakdown voltage than wet oxidation. Structural and semiconducting suicide properties were investigated before and after oxidation. High energy implantation of xenon was used in a marker experiment to investigate a possible change of oxidation mechanism between dry and wet oxidation.
Process-Dependent Electronic Structure at Metallized GaAs Contacts
Authors: Brillson L. J. , Vitomirov I. M. , Raisanen A. , Chang S. , Viturro R. E. , Kirchner P. D. , Pettit G. D. , Woodall J. M. 
Published: March 2011

ABSTRACTThe influence of metallization and processing on Schottky barrier formation provides the basis for one of several fruitful approaches for controlling junction electronic properties. Interface cathodo-and photoluminescence measurements reveal that electrically-active deep levels form on GaAs(100) surfaces and metal interfaces which depend on thermally-driven surface stoichiometry and reconstruction, chemical interaction, as well as surface misorientation and bulk crystal quality. These interface states are discrete and occur at multiple gap energies which can account for observed band bending. Characteristic trends in such deep level emission with interface processing provide guides for optimizing interface electronic behavior. Correspondingly, photoemission and internal photoemission spectroscopy measurements indicate self-consistent changes in barrier heights which may be heterogeneous and attributable to interface chemical reactions observed on a monolayer scale. These results highlight the multiple roles of atomic-scale structure in forming macroscopic electronic properties of compound semiconductor-metal junctions.
Pt3In7 Ohmic Contacts to n-TYPE GaAs
Authors: Swenson D. , Chang Y. A. 
Published: March 2011

ABSTRACTA thermodynamic and kinetic rationale was utilized to select Pt3In7 as an ohmic contact to n-GaAs. This analysis predicted that the contact metallurgy would be very simple and extremely uniform upon annealing. Preliminary electrical results showed that annealing samples at temperatures of 650 °C or higher led to ohmic behavior. A contact resistance of 3.4 × 10-5 Ω-cm2 was found upon annealing an uncapped contact at 750 °C for 15 s.
Chemical and Electrical Characterization of the CoGa/GaAs Interface as A Function of Temperature: A Thermally Stable Schottky Barrier up to 500°C
Authors: Alec Talin A. , Ngo Tue , Stanley Williams R. 
Published: March 2011

ABSTRACTX-ray diffraction studies and current-voltage measurements have been performed on a (100) oriented single crystal thin film of CoxGa1-x (x = 0.42) grown epitaxially on n-GaAs, from 300°C to 900°C. At this composition, CoxGa1-x, which has a broad range of homogeneity and a variable lattice parameter, is lattice matched to GaAs better than 0.5%. A Schottky barrier height of 0.68eV and an ideality factor of 1.07 have been measured up to 500°C, with significant barrier degradation at 600°C. At 700°C formation of the CoGa3 phase and a shift in CoxGa1-x stoichiometry to its bulk thermodynamically most stable composition of Co.45Ga.55 was observed with x-ray diffraction. At 800°C Co2AS formed, and at 900°C only CoGa3 and Co2As phases remained in contact with GaAs.
Metallurgical and Electrical Characteristics of MoAlx Schottky Contacts to n-GaAs
Authors: Huang T. S. , Peng J. G. , Lin C. C. 
Published: March 2011

ABSTRACTThe interfacial stability, surface morphology and electrical characteristics of MoAlx contacts to n-GaAs have been investigated by using x-ray diffraction, scanning electron microscopy, sheet resistance and current-voltage measurements. The compositions of rf-cosputtered MoAlx films were x = 0.35, 2.7, and 7.0, respectively. The contacts were annealed by rapid thermal processing in the temperature range 500–1000 °C for 20 s. The interfaces of MoAl0.35/GaAs and MoAl2,7/GaAs were stable up to 900 °C, while the interfaces of MoAl7.0/GaAs were less stable and reactions occurred above 800 °C. The variations of sheet resistances and the barrier heights of the Schottky diodes as a function of annealing temperatures can be well correlated to the interfacial stability. The MoAl2.7/n-GaAs diodes exhibited the best stability and were characterized by the highest barrier height (0.98 V) and nearly unit ideality factor (1.11) after annealing at 900 °C. For all thermally stable MoAlx/n-GaAs Schottky diodes, the barrier heights increased with annealing temperature.
Ge/Pd and Si/Pd/Ge/Pd Non-Alloyed Ohmic Contacts to InP Examined by Backside Secondary Ion Mass Spectrometry
Authors: Schwarz S. A. , Sands T. , Bhat R. , Koza M. , Pudensi M. A. A. , Wang L. C. , Lau S. S. 
Published: March 2011

ABSTRACTHigh resolution SIMS (secondary ion mass spectrometry) depth profiles of Ge/Pd and Si/Pd/Ge/Pd non-alloyed ohmic contacts on InP are obtained by sputter-etching from the back (semiconductor) side. The samples contain an InGaAs etch stop layer, to allow chemical thinning, and InGaAsP marker layers, which allow alignment and calibration of the depth profiles. Detailed comparisons are made to corresponding contacts on GaAs, processed and analyzed under similar conditions. The importance of interfacial alloy formation, semiconductor regrowth, and dopant incorporation are highlighted.
Ta-Si-N and Si3N4 Encapsulants for InP
Authors: Reid J. S. , Ruiz R. P. , Kolawa E. , Chen J. S. , Madok J. , Nicolet M -A. 
Published: March 2011

ABSTRACTThin films of sputtered, amorphous Ta36Si14N50 (a metallic conductor) and Si3N4 (an insulator) were evaluated as encapsulants for (100)-oriented InP substrates. Thicknesses of both films were approximately 100 nm. During a 15 min annealing in Ar, liberated phosphorus was gettered by a <Si>ISiO2ITa(100 nm) collector placed face-to-face on encapsulated or non-encapsulated InP. The stability of the InP with the encapsulant was characterized by backscattering spectrometry, scanning electron microscopy, and x-ray diffraction. As measured by 4He++ backscattering spectrometry, detectable amounts of phosphorus do not arise in the Ta collectors for the Ta-Si-N and Si3N4 encapsulation schemes until 650 and 700°C, respectively. Failure of the Ta36Si14N50 film is catastrophic at 700°C whereas the Si3N4 film degrades locally commencing at 600°C.
The Formation of TiN-Encapsulated Cu Interconnects
Authors: Li Jian , Strane J. W. , Russell S. W. , Chapman P. , Shacham-Diamand Y. , Mayer J. W. 
Published: March 2011

ABSTRACTA TiN(0)-encapsulated copper structure was made by annealing a Cu-10 at%Ti alloy film evaporated on a SiO2/Si(100) substrate in N2 or NH3 ambiente. During thermal cycling, the tensile stress in the nitridated films is in the range of 200 to 800 MPa. The stress relaxation depends on the cooling cycle and the presence of interlayer between film and substrate. A fast heating rate (70°C/min.) to 550°C in an NH3 ambient can effectively suppress the formation of Cu3Ti and enhance the TiNχ(0) formation near the surface of the copper film. This self-encapsulated Cu structure exhibits good adhesion to SiO2 and oxidation resistance. A fully encapsulated Cu fine line structure can be achieved by annealing a Cu-10at%Ti alloy film in an Ar ambient at 550°C and then in an NH3 ambient at 550°C to form TiOχ/Ti5Si3 adhesion layer and TiN(O) layer, respectively.