bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Photocarrier Grating and Its Applications in the Study of A-Si:H Materials and Devices
Authors: Balberg I. 
Published: March 2011

ABSTRACTTo date the photocarrier grating (PCG) technique is widespread among a- Si:H researchers. This technique is presently the only available technique for the determination of the minority carrier diffusion length in materials where this length is in the submicron range. The basic idea or the PCG technique will be presented, and results which follow its fruitful use in the study of a-Si:H materials and devices will be reviewed. Finally some future studies of these materials by the PCG method will be suggested.
The Extended State Mobility in Amorphous Silicon Alloys
Authors: Fauchet P.M. , Vanderhaghen R. , Mourchid A. , Hulin D. 
Published: March 2011

ABSTRACTThe total scattering time of free carriers injected optically in the extended states of amorphous semiconductors has been measured using the techniques of femtosecond time-resolved spectroscopy. We find that this scattering time is less than 1 femtosecond, independent of alloy composition (a-Si:H, a-Si,Ge:H, a-Si,C:H) and temperature (from 77 K to 400 K). The extended state mobility deduced from the measurement of the scattering time and of the effective mass is approximately 6 cm2/Vs. A model is proposed to explain these results
A Correlation between Si Surface Micro-Roughness and Atomic Concentration on Surface: Application to Micro-Roughness Measurement of Si
Authors: Oki I. , Biwa T. , Kudo J. , Shibayama H. 
Published: March 2011

ABSTRACTWe have developed a new method of evaluating Si surface micro-roughness, by forming thin oxide in HCI/H2O2 solution and then measuring the concentration of chlorine atoms or the total charge in this oxide. It is shown that this oxide does not affect the surface micro-roughness, and the surface concentration of chlorine atoms incorporated in this oxide and the total oxide charge are proportional to the surface micro-roughness, as obtained by AFM. From these correlations, it is possible to evaluate the surface microroughness for large areas compared with the areas of AFM measurement.
TXRF Characterization of Trace Metal Contamination in Thin Gate Oxides
Authors: Hockett R. S. , Hymes Diane 
Published: March 2011

ABSTRACTMetal contamination on the surface of silicon substrates before gate oxidation is known to affect gate oxide reliability. For the first time this study presents a non-destructive, analytical measurement of transition metals in an 8nm gate oxide grown by a 920 °C-10min-dry oxidation of an intentionally contaminated silicon surface. The TECHNOS TREX 610 TXRF anglescan of the gate oxide provides qualitative information on the location of the metals. The data indicate the Fe is on or in the oxide, the Cu is below the oxide, the Zn is on the oxide, and the Ni may be both in the oxide and below the oxide layer. In addition, quantitative estimates from the TXRF data indicate that all the original Fe and Cu are present, while only portions of Zn and Ni are detected after the oxidation.
In Situ Contamination Control Investigation of Silicon Nitride Low Pressure Chemical Vapor Deposition Process in Vertical Thermal Reactors
Authors: Moinpour Mansour , Bohannan K. , Shenasa M. , Sharif A. , Guzzo G. , Brestovansky D.F. , Markle R.J. , Wilkes R. 
Published: March 2011

ABSTRACTA contamination control study of a Silicon Valley Group Thermco Systems Vertical Thermal Reactor(VTR) is presented. Trace elements of contaminants such as water vapor and oxygen have been shown to significantly affect the integrity of the silicon nitride film deposited by the low pressure chemical vapor deposition (LPCVD) process. This study documented the effects of process parameters on gaseous contamination levels, i.e., O2 and H2O vapor. Starting with a baseline process, the effects of an excursion of pre-deposition temperature ramp-up and stabilization condition, wafer load/unload and various post deposition conditions were explored. An axial profile of moisture and oxygen levels along the wafer load was obtained using Linde's Low Pressure Reactor Analysis(LPRAS) methodology. In addition, other process parameters such as gas flow rates during load and unload of wafers, pre-deposition N2 purge and process tube exposure time to ambient environment were- investigated. The wafers were analyzed for contaminants on the wafer surface or in the deposited silicon nitride film using FTIR and Auger spectroscopy techniques. They showed low levels of Si-O and no measurable Si-H or N-H bonds.
Surface Characterization of Chemical-Mechanical Polished GaAs by Inclined Bragg Plane Triple Crystal X-Ray Diffraction
Authors: Wang Victor S. , Matyi Richard J. 
Published: March 2011

ABSTRACTThe incorporation of triple crystal x-ray diffraction (TCD) under conditions of a nearly grazing incident x-ray beam provides a unique capability to characterize surface and subsurface structural damage. The effects of bromine-methanol chemical-mechanical (CM) polishing on the surface quality of GaAs were investigated by inclined Bragg plane triple crystal x-ray diffraction. GaAs samples polished under varying conditions of Br2 concentration, total polish time, polish wheel rotation speed, and force exerted on the samples were analyzed using TCD profiles from inclined (220) planes, with the samples oriented at both the exact Bragg condition, θB, and at deviations from the exact Bragg condition. As the deviation from the 220 reciprocal lattice point was increased, multiple peaks corresponding to both the dynamic and the kinematic components were observed. The peak positions and the relative intensities of the various peaks were used to characterize the effects of the CM polishing variables on the GaAs surfaces.
Surface Characterisation of Si After HF Treatments and its Influence on the Dielectric Breakdown of Thermal Oxides
Authors: Verhaverbeke S. , Alay J. , Mertens P. , Meuris M. , Heyns M. , Vandervorst W. , Murrell M. , Sofield C. 
Published: March 2011

ABSTRACTThe characteristics of the HF-treated Si-surface are investigated as a function of dipping time in dilute HF solutions. It is found that the contact angle is a very sensitive measure for the degree of oxidation of the Si-surface. The importance of obtaining a perfectly passivated surface in order to reduce the particle deposition on the surface is shown. HF-last cleans are found to be beneficial in terms of metallic contamination and gate oxide integrity. The importance of the loading ambient in furnaces is investigated after HF-treatments and RCA-cleans.
In Situ Low Temperature Cleaning and Passivation of Silicon by Remote Hydrogen Plasma for Silicon-Based Epitaxy
Authors: Banerjee S. , Tasch A. , Hsu T. , Qian R. , Kinosky D. , Irby J. , Mahajan A. , Thomas S. 
Published: March 2011

ABSTRACTRemote Plasma-enhanced Chemical Vapor Deposition (RPCVD), which involves nonthermal, remote plasma excitation of precursors, has been demonstrated to be a novel and attractive technique for low temperature (150-450C) Si and Sil-xGex epitaxy for applications in Si ULSI and novel Si heterostructure devices which require compact doping profiles and/or heterointerfaces. An in situ low temperature remote hydrogen plasma clean in the Ultra-High Vacuum (UHV) deposition chamber in order to achieve a chemically passive, hydrogenated Si surface with minimal O, C and N contamination, is a critical component of the process. The ex situ wet chemical cleaning consists of ultrasonic degreasing and a modified RCA clean, followed by a final dilute HF dip. The in situ clean is achieved by remote plasma excited H, where H introduced through the plasma column is r-f excited such that the plasma glow does not engulf the wafer. In situ AES analysis shows that the remote H plasma clean results in very substantial reduction of the C, O and N contamination on the Si surface. We believe that the H plasma produces atomic H which, in turn, produces a reducing environment and has a slight etching effect on Si and SiO2 by converting them to volatile byproducts. TEM analysis of the wafers subjected to this clean indicate that defect-free surfaces with dislocation loop densities below TEM detection limits of 105 /cm2 are achievable. Corroborating evidence of achieving an atomically clean, smooth Si surface by remote H plasma clean as obtained from in situ RHEED analysis will also be presented. After in situ H cleaning at low pressures (45 mTorr), typically for 30 min. at a substrate temperature of 310 C, we observe both stronger integral order streaks compared to the as-loaded sample and the appearance of less intense half-order lines indicative of a (2 × 1) reconstruction pattern, indicating a monohydride termination. A (3 × 1) reconstruction pattern is observed upon H plasma clean at lower temperatures (250 C), which can be attributed to an alternating monohydride and dihydride termination. Results of air exposure of hydrogenated Si surfaces by AES analysis indicate that the (3 × l) termination is chemically more inert towards readsorption of C and 0. Successful Si homoepitaxy and Si/Sil-xGex heteroepitaxy under a variety of surface cleaning conditions prove that by a combination of these cleaning techniques, and by exploiting the inertness of the H-passivated Si surface, very low defect density films with 0 and C levels as low as 1X1018 cm−3 and 5×1017 cm−3, respectively, can be achieved.
Vapor HF Etching for Low Temperature Silicon Epitaxy
Authors: D'Emic Christopher P. , Blum Joseph M. , Cohen Susan L. , Baseman Robert J. , Gilbert Monica , Cardone Frank , Stanis Carol , Rothman Laura , Hill Michael , Krusell Wilbur 
Published: March 2011

ABSTRACTWe have evaluated the use of HIF vapor cleaning using an Advantage Edge 2000 commercial etcher as a preclean for low temperature UHV/CVD silicon epitaxy (LTE). Surface analysis by contact angle, XPS and Optically Stimulated Electron Emission (OSEE) measurements indicate that vapor HF treated surfaces have higher levels of impurities and are less stable than surfaces dipped in 10:1 diluted HF. Interfacial SIMS measurements and defect analysis using plan-view TEM after epitaxial growth indicate that the vapor treated samples also had higher levels of interfacial oxygen and surface defects. The results indicate that vapor HF precleaning is less effective for LTE than an aqueous HF dip since it provides poorer quality hydrogen passivation of the silicon surface.
Characterization of SiGe Epitaxial Films Using Ellipsometry and X-Ray Fluorescence
Authors: Munukutla L.V. , Evans K. , Liaw M.H. 
Published: March 2011

ABSTRACTEllipsometry in combination with X-ray fluorescence spectroscopy is demonstrated as a suitable technique to characterize SiGe thin films (180–800 Å) rapidly and nondestructively. Film thickness values extracted from ellipsometry are in agreement with the measurements obtained using other techniques such as TEM, SIMS, and RBS. The measured Ge concentration obtained by direct excitation of X-rays in several SiGe films ranging from 6 to 20 atomic percent, shows good correlation with the values obtained using RBS and SIMS.
Pre-Oxidation Anneal Kinetics: Interface Degradation of Thin SIO2 Films on Silicon
Authors: Poler J.C. , Irene E.A. 
Published: March 2011

ABSTRACTThe high temperature anneal of hydrogen terminated silicon has been shown to etch and roughen its surface. We attempt to describe the degree of this roughness and the time scale on which it occurs using several electrical measurements: excess direct tunneling currents, dielectric breakdown and the oscillations in the Fowler-Nordheim tunneling currents. From these results we draw conclusions on the time and water content dependence of pre-oxidation annealing on the microroughness of the Si/SiO2 interface.
Actinide and Technetium Solubility Limitations in Groundwaters of Crystalline Rocks
Authors: Allard B. 
Published: March 2011

ABSTRACTThe solubility and speciation of U, Np, Pu, Am and Tc in deep groundwaters from crystalline rocks have been calculated. The solution chemistry of these elements is largely determined by the redox conditions (Eh = 0.24 − 0.06pH ± 0.06 V, based on measurements of Fe(II)), pH (usually 7 − 9) and the presence of carbonate (log [CO32-] from (pH − 14) to (0.76pH − 10.83), based on measurements of HCO3-). The oxidation states U(IV)(+VI), Np(IV), Pu(III)(+IV), Am(III) and Tc(IV) dominate, with the tetravalent oxides (U, Np, Pu, Tc) and Am2(CO3)3(s) as solubility limiting phases. Maximum concentrations in the range 10-9− 10-10M or below would be expected for U, Np and Tc under reducing conditions, somewhat higher for Pu and still higher (10-6− 10-7M) for Am.
Design Considerations To Minimize The Impact Of A Repository On A Host Rock
Authors: Scully Leo W. 
Published: March 2011

ABSTRACTA conceptual design is being developed in support of the Department of Energy's study of a potential site for a nuclear waste repository at Yucca Mountain. This design can be used to support the recommendation of that site for characterization if so designated by the Department of Energy. In the event that the Yucca Mountain site is chosen for development as the first repository, the conceptual design and subsequent preliminary engineering designs could be used to develop design specifications for repository construction. The design addresses the unique surface and subsurface characteristics of the volcanic tuffs at Yucca Mountain. A candidate horizon has been identified approximately 300 meters below the surface and about 100 meters above the water table.The design activities are being conducted in a manner to attempt to control and reduce to the extent practicable the impact exerted by the repository on the containment and isolation capability of the site. This process consists of careful iteration of design, analysis and interpretation of results to ensure long-term containment and isolation requirements are met and that short-term operations and costs are acceptable.
Colloid Generation and the Actinide Migration in Gorleben Groundwaters
Authors: Kim J.I. , Buckau G. , BaumgÄrtner F. , Moon H.C. , Lux D. 
Published: March 2011

ABSTRACTThe generation and behaviour of realcolloids and pseudocolloids of the actinides, 238 pu, 241Am and 244Cm, are investigated in four different Gorleben Groundwaters. Colloids are characterized by ultrafiltration at different pore sizes from 1 nm to 450 nm and various analytical instrumentations. Behaviour of pseudocolloids has been analysed by determining their effects on the solubility and the distribution coefficient of actinides between groundwater and geomatrix. Sorption of actinide ions on groundwater-colloids (generation of pseudocolloid) are examined and the migration of actinides as pseudocolloids is discussed.
Geotechnical Materials Considerations for Conceptual Repository Design in the Palo Duro Basin, Texas
Authors: Versluis W. S. , Balderman M. A. 
Published: March 2011

ABSTRACTThe Palo Duro Basin is only one of numerous potential repository locations for placement of a nuclear waste repository. Conceptual designs in the Palo Duro Basin involve considerations of the character and properties of the geologic materials found on several sites throughout the Basin. The first consideration presented includes current basin exploration results and interpretations of engineering properties for the basin geologic sequences.The next consideration presented includes identification of the characteristics of rock taken from the geologic sequence of interest through laboratory and field testing. Values for materials properties of representative samples are obtained for input into modeling of the material response to repository placement. Conceptual designs which respond to these geotechnical considerations are discussed.
Geohydrology Surrounding a Potential High Level Nuclear Waste Repository in the Palo Duro Basin, Texas
Authors: Deyling M. A. 
Published: March 2011

ABSTRACTThe Palo Duro Basin of the Texas Panhandle is being investigated as a potential high level nuclear waste repository site. Groundwater is the most likely mechanism for radionuclide movement, therefore, it is desirable to locate a repository in a hydrologic regime which is favorable for waste isolation and containment. The Palo Duro Basin consists of deep brine aquifers underlying a thick Permian age evaporite section. Overlying the Permian age evaporites are the Dockum and Ogallala fresh water aquifers.Observed potentiometric data in the principal aquifers indicate a potential for downward flow from the surficial aquifers to the deep brine aquifers. Groundwater movement in these deep aquifers is very slow. Modeling efforts indicate flow times of hundreds of thousands to over a million years for groundwater to reach the basin margins.Investigative methods have included drill-stem testing similar to oil field methodology, modified drill-stem testing with tools developed for low-permeability formations and long-term production tests similar to conventional water well pumping tests. Testing has generally indicated permeability of .1-10 millidarcies in the water transmitting units.
Surface Layer Crystallization of Simulated Waste Glass at Elevated Temperatures
Authors: Inoue Tadashi , Yokoyama Hayaichi , Onchi Takeo , Kōyama Hiroaki 
Published: March 2011

ABSTRACTSurface crystallization was investigated for alkali borosilicate glass containing simulated waste of 26.4 wt% in the temperature range of 550 to 800°C. The crystals deposited on the surface layer of glasses were mainly composed of molybdates and molybdenum oxide. The saturated crystalline fraction of eash deposit, except for KMOO4, was maximum at 800°C in the temperature range investigated, and decreasing with decreasing temperature. The fractional change of crystallization was evaluated with the JMA equation. The activation energy of surface crystallization was estimated to be in the range of 50 to 70 kcal/mol for most of molybdates.
Longevity of Borehole and Shaft Sealing Materials: Characterization of Ancient Cement Based Building Materials
Authors: Langton Christine A. , Roy Della M. 
Published: March 2011

ABSTRACTDurability and long-term stability of cements in plasters, mortars, and/or concretes utilized as borehole plugging and shaft sealing materials are of present concern in the national effort to isolate nuclear waste within deep geological repositories. The present study consists of an examination of selected ancient building materials and provides insights into the durability of certain ancient structures. These data were combined with knowledge obtained from the behavior of modern portland cements and natural materials to evaluate the potential for longevity of such materials in a borehole environment. Analyses were conducted by petrographic, SEM, chemical, and x-ray diffraction techniques.
Cement-Based Waste forms for Disposal of Savannah River Plant Low-Level Radioactive Salt Waste
Authors: Langton Christine A. , Dukes Michael D. , Simmons Randolph V. 
Published: March 2011

ABSTRACTDefense waste processing at the Savannah River Plant will include decontamination and disposal of approximately 100 million liters of soluble salts containing primarily NaNO3, NaOH, NaNO2, NaAl(OH)4, and Na2SO4. A cement-based waste form, “saltstone,” has been designed for disposal of Savannah River Plant low-level radioactive salt waste. Bulk properties of this material have been tailored with respect to salt leach rate, permeability, and compressive strength. Microstructure and mineralogy of leached and unleached specimens were characterized by SEM and X-ray diffraction analyses, respectively. It has been concluded that the salt leach rate can be limited so that amounts of salt and radionuclides in the groundwater at the perimeter of the 100 acre disposal site will not exceed EPA drinking water standards.
In-Can Hot Pressing of Borosilicate Glass for the Immobilization of Highand Medium-Level Wastes
Authors: Ondracek G. , Toscano E.H. 
Published: March 2011

ABSTRACTThe paper presents a method for the immobilization of different waste streams based in the uniaxial in-can hot pressing of a glass frit together with the waste oxides.The process reported herein offers engineering simplicity in combination with many technological advantages such as significant decrease in temperature, use of small pressure, improved homogeneity of the products, production in easily arrangeable and interchangeable units. Furthermore, the proposed method has also proved to be suitable for treating intermediatelevel waste streams containing Zry-4 cladding fragments.
An Experimental and Modelling Approach of the Near Field Release and Transport Processes
Authors: Lanza F. , Saltelli A. 
Published: March 2011

ABSTRACTA simple mathematical model has been set up assuming that the glass leaching is defined by the diffusion and adsorption of the SiO2 in the porous media. It is also assumed that at the contact with the glass, the SiO2 content in the leachant reaches the saturation limit. Experimental weight losses seem to be in good agreement with the calculated values. In order to pass from the leaching rate of the glass to the release of radioactivity, the different radionuclides are subdivided into three different classes following their leaching rate and saturation limit. These three classes are discussed separately. An experiment which allows to measure leaching rate and diffusion of the various elements has been set up. Preliminary results are presented and discussed.
Methods of Simulating Low Redox Potential (Eh) for a Basalt Repository
Authors: Jantzen Carol M. 
Published: March 2011

ABSTRACTIn the selection of a repository for burying vitrified nuclear waste, the leach rate of the waste form in groundwater is of concern. Basaltic groundwaters have inherently low redox potentials which may affect the waste form leach rate. Laboratory simulation of the Eh-pH conditions to be found in a basalt repository can be achieved when crushed basalt is added to deoxygenated deionized water. The effects of other redoxactive waste package components, such as iron, were found to stabilize solution redox potential at different valves under oxic and anoxic conditions. When iron was present, different waste form leach rates were observed with and without oxygen.
The Relationship Between Reaction Layer Thickness and Leach Rate For Nuclear Waste Glasses
Authors: Chick L. A. , Pederson L. R. 
Published: March 2011

ABSTRACTThree leaching tests, devised to distinguish among several proposed nuclear waste glass leaching mechanisms, were carried out for four different waste glasses. In the first test, the influence of a pre-formed reaction layer on elemental release was evaluated. In the second test, glass specimens were replaced with fresh samples halfway through the leaching experiment, to evaluate the influence of the concentration of glass components in leaching. Finally, regular replacement of the leachant at fixed time intervals essentially removed the variable of changing solution concentration, and allowed an assessment of the influence of reaction layer thickness on the leaching rate. Results for all glasses tested indicated that the reaction layer presented little or no barrier to leaching, and that most of the retardation on leaching rates generally observed are attributable to saturation effects.