bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrogenated Amorphous Silicon Films by the Pyrolysis of Disilane(1)
Authors: Chu T. L. , Chu Shirley S. , Ang S. T. , Lo D. H. , Duong A. , Hwaung C. G. , Book L. 
Published: March 2011

AbstractThe thermal decomposition of disilane in a hydrogen or helium flow has been used for the deposition of hydrogenated amorphous silicon (a-Si:H) films on the surface of several substrates at 450°-500°C. The concentration of disilane in the reaction mixture has been found to affect strongly the deposition rate and the photoconductivity of a-Si:H films. The AMI conductivity of a-Si:H films increases with increasing disilane concentration and approaches lO−5(ohm-cm)−l at disilane concentrations higher than about 4%, and the conductivity ratio is about lO5. The density of gap states in CVD a-Si:H films have been determined by the photothermal deflection spectroscopy, capacitancetemperature, capacitance-frequency, and space-charged-limited current measurements with similar results.
High Performance A–Si Solar Cells and Narrow Bandgap Materials
Authors: Nakano Shoichi , Kishi Yasuo , Ohnishi Michitoshi , Tsuda Shinya , Shibuya Hisashi , Nakamura Noboru , Hishikawa Yoshihiro , Tarui Hisaki , Takahama Tsuyoshi , Kuwano Yukinori 
Published: March 2011

AbstractHigh performance a-Si solar cells were developed. A conversion efficiency of 11.5% was achieved for a textured TCO/p-SiC/in/Ag structure with a size of 1 cm2 using the high quality i-layer fabricated by a new consecutive, separated reaction chamber apparatus. A conversion efficiency of 9.0% was obtained with a size of 10cm × 10cm. A high quality a-SiGe:H:F, which is a new narrow bandgap material for a-Si solar cells, was fabricated by a glow discharge decomposition of SiF4 + GeF4 + H2.A photo-CVD method was investigated in order to improve the interface properties of a–Si solar cells. A conversion efficiency of 11.0% was obtained with a solar cell in which the p-layer is fabricated by the photo-CVD method. a-SiGe:H films were fabricated by the photo-CVD method for the first time as a narrow bandgap material for multi-bandgap a-Si solar cells.
Light-Induced Metastable Defects in a-Si:H: Towards an Understanding
Authors: Stutzmann Martin , Jackson Warren B. , Tsai Chuang Chuang 
Published: March 2011

AbstractThe dependence of the creation and the annealing of metastable dangling bonds in hydrogenated amorphous silicon on various material parameters will be discussed in the context of a recently proposed model. After a brief review of the kinetic behaviour governing defect creation and annealing in undoped a- Si:H, a number of special cases will be analyzed: the influence of alloying with O, N, C, and Ge, changes introduced by doping and compensation, and the role of mechanical stress. Finally, possibilities to increase the stability of a-Si:H based devices will be examined.
Continued Development of R.F. Sputtered a-Si:H Thin-Film Transistors Towards an All-Sputtered Device
Authors: Allison J. , Turner D.P. , Cousins D.C. 
Published: March 2011

AbstractPrototype thin film transistors have previously been fabricated by r.f. magnetron sputtering of a-Si:H on to CVD Si02 using a crystalline silicon gate. These devices exhibited an on/off current ratio of four orders of magnitude for gate voltages as low as 10 volts. This demonstrated the suitability of the sputtered layer for liquid crystal display applications.The use of a crystalline substrate negates the advantages of using a thin film,such as large area capability and low cost, so we have turned our attention to the provision of a sputtered dielectric. Several candidate materials have been considered, including Si02, Si3N4, Ta205, AIN and Ti02. We present the characteristics of our first all-sputtered transistor utilising an Si02 gate,and assess the dielectric properties and potential of other materials, with emphasis on the silicon oxynitride system.
Amorphous Silicon Linear Image Sensor
Authors: Ozawa T. , Takenouchi M. , Tomiyama S. 
Published: March 2011

AbstractDocument width linear image sensor arouse strong and wide interest as a compact image reading component for facsimile and other document readers. Among those, a-Si:H is excellent in stability and light sensitivity. The photosensing element of those sensors have a sandwich-like structure which consist of Cr/i-a-Si:H/ITO. In this structure, i-a-Si:H/ITO shows good shottky contact resulting high photo to dark current ratio and fast photoresponse. We have been developing linear image sensor of A4 and B4 size with resolutions of 8dot/mm and l6dot/mm and had applied successfully to facsimile and image input terminals.
Amorphous Si:H Heterojunction Photodiode and its Application to a Compact Scanner
Authors: Kaneko S. , Kajiwara Y. , Okumura F. , Ohkubo T. 
Published: March 2011

AbstractThis paper reports heterojunction photodiode properties and its application to a compact scanner. The photodiode has ITO / p-a-SiC:H / a-Si:H / metal structure. This diode has high photo to dark current ratio and small photocurrent saturation voltage, because of the excellent blocking characteristics for a heterojunction with large built in potential. Moreover, a-Si:H / metal contact has been investigated. A contact linear image sensor has been fabricated using the heterojunction photodiode array and compact optical system. Performance tests showed excellent results. Good reproduced images have been obtained.
Electrical and Optical Properties of PECVD Amorphous Silicon Grown at Low Frequencies
Authors: Piper W.W. , Possin G.E. 
Published: March 2011

AbstractThe semiconducting properties of a-Si are ideally suited for making a switch to control the matrix addressing of an array of liquid crystal pixels. This investigation explores the differences between a-silicon deposited by plasma enhanced chemical vapor deposition at 13.56MHz and at 60KHz. The bonded hydrogen concentration, the index of refraction and the optical band gap of a-Si have been measured. The device used to explore the field effect mobility of a-Si is an inverted staggered FET fabricated on a glass substrate with conventional photolithography.
Photoemission Studies of Amorphous Silicon/Germanium Heterojunctions
Authors: Evangelisti F. , Modesti S. , Boscherini F. , Fiorini P. , Quaresima C. , Capozi M. , Perfetti P. 
Published: March 2011

AbstractThe heterostructures obtained by growing a-Ge on a-Si:H and a-Si have been investigated by synchrotron radiation photoemission. We measured valence band and core level spectra on the heterostructures grown in situ under ultrahigh-vacuum conditions. A step-by-step monitoring of possible band-bending changes during the interface formation enabled us to determine unambiguously the band discontinuities. The measured values of the valence band discontinuity were 0.2 ± 0.1 eV for a-Si:H/a-Ge and 0.0 ± 0.1 eV for a-Si/a-Ge, respectively. Evidence was found for the formation of abrupt interfaces without interdiffusion.
Electrical and Structural Properties of Grain Boundary in Polycrystalline Si
Authors: Young R. T. , Narayan J. , Chang Y. K. 
Published: March 2011

ABSTRACTA special type of high angle grain boundary with mirror symmetry of the crystallographic orientation between the two grains is examined electrically and structurally. Transmission electron microscopy investigations show the nonuniform nature of the grain boundary. Both coherent and incoherent regions are observed along the boundary plane, and the types of dislocations and their densities vary from place to place. Electrical measurements of the boundary properties indicate no measurable barrier height. Heat treatment of the sample in an oxygen atmosphere at 950°C for 30 min did not change the boundary resistance. However, recombination effects are enhanced after boron diffusion. When pulsed laser radiation was used to process this material, it was found that the grain boundary structures were modified by laser-induced surface melting, i.e., incoherent boundaries were converted to coherent boundaries in the melted region.
Characterization of Grain Boundaries in Polycrystalline GaAs
Authors: Spencer Michael G. , Schaff William J. , Ken Wagner D. 
Published: March 2011

ABSTRACTExamination of capacitance transients arising from the emission or capture of electrons at a charged GaAs grain boundary reveal for the first time the existence of discrete interface levels. The position of these levels in the bandgap and their associated capture cross sections are determined from the transients.
Grain Boundary Passivation in Polycrystalline Silicon : A D.L.T.S. Study
Authors: Srivastava Prakash C. , Bourgoin Jacques C. 
Published: March 2011

ABSTRACTAfter treatment in a deuterium plasma, the D.L.T.S. spectrum associated with grain boundaries in p–type Si is found to reduce to a narrow band centered at 0.32 ± 0.02 eV with a total density of 5 ⨉ 1015 cm−2 . However, the capture cross-section, measured to be ∼ 2 × 10−20 cm2 , is 10 times larger than the apparent cross-section associated with the states present in unpassivated material.
Ebic/Tem Investigation of Defects in Solar Cell Silicon
Authors: Ast Dieter G. , Cunningham Brian , Strunk Horst 
Published: March 2011

ABSTRACTTwo examples are given of the application of EBIC and HVTEM to the study of defects in silicon.An hexagonal dislocation network in a coherent first order twin boundary in WEB silicon shows a three fold symmetry when imaged by EBIC. The observed variation of the minority carrier lifetime at the nodes is consistent with a model which assumes that jogs are particularly strong recombination sites at a dislocation.EBIC and STEM observations on unprocessed and processed EFG ribbon show that the phosphorus diffused junction depth is not uniform, and that a variety of chemical impurities precipitate out during processing. Two kinds of precipitates are found i) 10 nm or less in size, located at the dislocation nodes in sub-boundary like dislocation arrangements formed during processing and ii) large precipitates, the chemical composition of which has been partially identified. These large precipitates emit dense dislocations tangles into the adjacent crystal volume.
An Enhanced Photoresponse at Dislocation Subgrain Boundaries Revealed by X-Ray Topography of Polysilicon Solar Cells
Authors: Johnson S.M. , Armstrong R.W. , Rosemeier R.G. , Storti G.M. , Lin H.C. , Regnault W.F. 
Published: March 2011

ABSTRACTAn enhanced photoresponse at dislocation subgrain boundaries (in comparison with grain boundaries and dislocation-associated twin boundaries) is attributed to an increased junction depth at their positions relative to the value of the minority carrier diffusion length, Ln. For reasonably pure material, Ln is determined by the dislocation density. The dislocation microstructure of polysilicon solar cells is advantageously studied by means of the several x-ray topography techniques.
High Resolution Electron Microscopy of Grain Boundaries in Silicon
Authors: Cunningham B. , Ast D. 
Published: March 2011

ABSTRACTThe lattice imaging technique has been used to study grain boundaries in annealed, chemically vapor deposited (CVD) silicon. The majority of the grain boundaries are Σ*=3, 9 or 27, i.e. they are all twin related, and have boundary planes which coincide with high density planes of the appropriate coincidence site lattice (CSL). Asymmetric Σ=27 boundaries are found to be dissociated on an atomic scale into faceted Σ=3 boundaries and Σ=9 boundaries. No dissociation of the Σ=27 boundaries is observed when the boundary planes are symmetric.
Theory of Mosfet Operation in Small-Grain Polysilicon
Authors: Depp S. W. , Huth B. G. , Juliana A. , Koepcke R. W. 
Published: March 2011

ABSTRACTThe operation of a MOSFET transistor fabricated in undoped, small-grain polysilicon is considered, and a model is developed which can predict threshold and drain current as a function of gate voltage. A two-dimensional calculation is described for the band-bending under the influence of a gate potential with the assumption that the grain boundaries are repetitive and oriented at right angles to the gate-oxide/polysilicon interface. Both hole and electron traps are assumed present at the grain boundaries and are coincident in energy with the intrinsic Fermi level at room temperature. An energy barrier to the flow of carriers is present in the undoped polysilicon, and the magnitude of this energy barrier is dependent on the gate voltage. The band-bending occurs over much shorter distances than the intrinsic Debye length, and the trapped charge at the grain boundaries behaves very similarly to the charged impurities in a depletion model. The two-dimensional model can be approximated by a one-dimensional calculation for the band-bending by making the assumption that the trapped charge is uniformly distributed throughout the grain. The results of this calculation can be used to calculate the magnitude of the free carriers in the channel region. Using this information, the dependence of the potential barrier on gate voltage, and the gradual channel approximation for an FET, one can compute the drain current vs. gate voltage, and the results of these calculations are given for parameters used in fabricating actual devices. Finally, experimental results are compared with the model for typical transistors fabricated in undoped, small-grain polysilicon.
Electronic Properties of ZnO Varistors: A New Model
Authors: Pike G. E. 
Published: March 2011

ABSTRACTMuch of the research on ZnO varistors has concentrated on the explanation of their dc current-voltage characteristics. However, varistors also have unusual ac properties which can be technologically important, and must be described by any comprehensive model. In an ideal varistor with identical grain boundaries throughout, there should be no dispersive capacitance at zero bias. In real varistors this capacitance varies considerably with frequency. This dispersion has two causes, charge trapping in the depletion regions and differing grain boundary barriers. Calculations for each process are given. For voltages well below the varistor breakdown value, the low frequency capacitance increases with applied voltage. At even higher voltages the capacitance turns over and becomes negative. All of these effects can be described with a double depletion layer/thermionic emission model. The anomalous capacitance behavior with bias is due to the modulation of the potential barriers by charge trapping at the grain boundaries. In the varistor breakdown regime minority carriers created by impact ionization are important.
Degradation of Zinc Oxide Varistors
Authors: Takahashi Ken , Miyoshi T. , Maeda K. , Yamazaki T. , Ohwada S. 
Published: March 2011

ABSTRACTThe effect of ambient gases on degradation and rejuvenation of ZnO varistors was investigated from the viewpoint of voltage-current characteristics. Ambient oxygen gas suppressed increases in the leakage current during ac biasing, while it rejuvenated degraded samples. The time dependence of rejuvenation indicated that ion migrations, possibly the desorption and adsorption of oxygen ions at the grain boundaries, occur reversibly in degradation and rejuvenation. Moreover, a noticeable difference was observed between V–I curve shapes after ac biasing in nitrogen and in oxygen atmospheres.
The Electrical Activity at Twin Boundaries in Silicon
Authors: Cunningham B. , Strunk H.P. , Ast D.G. 
Published: March 2011

ABSTRACTAlthough coherent twin boundaries in silicon are electrically inactive, dislocations in the boundaries can act as efficient recombination centers for minority carriers. Different twin boundary dislocation arrangements have been studied by EBIC and TEM. It is found that the observed EBIC contrast is dependent not only on the arrangement of the dislocations in the boundaries but also on the inclination of the boundaries to the surface. It is shown that different defect configurations can produce similar EBIC contrast.
Space Charge Contribution To Solute Segregation Near Grain Boundaries
Authors: Yan M. F. , Cannon R. M. , Bowen H. K. 
Published: March 2011

ABSTRACTThe interaction potentials between solutes and grain boundaries in ionic solids are identified as [1] the electrostatic interaction between the charged solutes and grain boundaries and [2] the elastic energy due to size misfit of solutes in the matrix. Equilibrium solute distribution is calculated from the defect distributions leading to the minimum free energy. Space charge distributions near interfaces during kinetic processes are evaluated. We analyze the limiting case of constrained equilibrium in which the vacancy distribution and degree of solute-vacancy association satisfy a minimum free energy under the constraint of no solute redistribution.
Effects on Fissure Calcite by Recharge Water - Some Problems Related to 14C-Dating of Groundwater
Authors: Tullborg Eva-Lena 
Published: March 2011

AbstractThe modelling of water flow in the bedrock is of especial importance for safetyassessementof radioactive waste disposal in crystalline rocks. Age dating of the water has been tried for the validation of ground water transport models. Thus, several tritium and 14C-analyses have been carried out on water samples from deep boreholes drilled within SKB's (Swedish Nuclear Fuel and Waste Management Company) study sites. However, several processes will influence the final content of 14C in the groundwater measured and correction for enrichment and dilution are hard to carry out. Another contribution to the understanding of recharge water transport by using frequency and stable isotope analyses of calcite fissure fillings is suggested.
Chemical Thermodynamic Data Set for Minerals Associated With Granite
Authors: Muller A. B. , Fritz B. , Wyman A. , Snellman M. 
Published: March 2011

AbstractThe OECD Nuclear Energy Agency is coordinating the development of a critically reviewed CODATA compatible chemical thermodynamic data base for ten radioelements important to various areas of nuclear technologies. Such a data base in itself is insufficient for modeling the speciation and solubility behaviour of radioelements in natural rock/water systems. Data must also be available for describing the rock phases present, which determine to a large extent the physico-chemical environment. Since a number of NEA Member countries are contemplating nuclear waste disposal in granitic environments, a data base for seventy-three minerals associated with granite is presented here, as a complement to the data base work on radioelements.
Weathered Basalt Glass: A Natural Analogue for the Effects of REACTION Progress on Nuclear Waste Glass Alteration
Authors: Grambow B. , Jercinovic M. J. , Ewing R. C. , Byers C. D. 
Published: March 2011

AbstractLaboratory experiments alone cannot be used to verify models for the long-term release of radionuclides from nuclear waste glasses. Basalt glasses have been proposed as an appropriate natural analogue for the long-term validation of release models [1]. Their analogous behavior has been demonstrated in laboratory experiments in which both types of glasses display similar reaction rates, alteration products and surface layer morphologies [2,3]. This paper illustrates how empirical data from natural occurrences of basalt glass can be interpreted by a model which is developed to describe the reaction progress of the corrosion of nuclear waste form borosilicate glass [4,5].
Oxidation of Candu UO2 Fuel by the Alpha-Radiolysis Products of Water
Authors: Shoesmith D. W. , Sunder S. , Johnson L. H. , Bailey M. G. 
Published: March 2011

AbstractThe oxidation of CANDU fuel (UO2) by the alpha-radiolysis products of water has been investigated using electrochemical and X-ray photoelectron spectroscopic-experiments. Experiments with O2 and H2O2, two of the expected products of radiolysis of water, indicate that the rate of oxidation of UO2 by H2O2 is about 200 times faster than by dissolved oxygen. Oxidation by both H2O2 and O2 shows pH dependence. Possible reaction paths for the oxidation of UO2 by radiolysis products are discussed.
Structural Changes in 238Pu-Substituted Zirconolite on Recovery from the Metamict State
Authors: Clinard F. W. , Livak R. J. , Hobbs L. W. , Rohr D. L. 
Published: March 2011

Abstract238Pu-substituted zirconolite (CaPuTi2O7) was held at ≈350 K for a time sufficient to allow self-irradiation damage to convert the material to the metamict condition. Samples were then stored at 875 K, while dimensional and microstructural changes were monitored by dilatometry and transmission electron microscopy. Densification proceeded sporadically over a period of ≈400 days, attaining a final value of 4 vol% as a result of crystallization. The material was found to be friable at an intermediate stage of recovery, apparently as a result of internal strains. Evidence is presented that CaPuTi2O7 can exist in more than one metamict state, depending on extent of prior damage and thermal history.
Some Aspects on the Use of Iron Canisters for HLW
Authors: Neretnieks Ivars 
Published: March 2011

AbstractIron canisters for high level nuclear waste embedded in compacted bentonite in deep geologic repositories will corrode forming hydrogen gas. The equilibrium pressure (when corrosion would stop) has been estimated to be between 500 and 1000 atm. under repository conditions. As this is much higher than the lithostatic pressure (weight of rock overburden) the gas must be allowed to escape before it disrupts the repository. Escape by diffusion alone is not sufficient but recent experiments have demonstrated that the larger pores in the bentonite are blown free of water and let the gas escape before excessive pressures build up.The potential effect of a capillary breaking layer (CBL) has been explored. A fine layer nearest the canister (e.q. quartz sand) would have much lower capillary suction pressures than the bentonite clay and would keep the water out as long as there is sufficient overpressure. As long as the CBL is void of liquid water no radionuclides can escape, even if the canister is penetrated.
Simulation of Water Transport in Heated Rock Salt
Authors: Schlich M. , Jockwer N. 
Published: March 2011

AbstractThis paper summarizes computer simulation studies on water transport in German rock salt. Based on JOCKWERS's experimental investigations on water content and water liberation, the object of these studies was to select a water transport model, that matches the water inflow which was measured in some heater experiments in the Asse Salt Mine. The main re-sult is, that an evaporation front model, with Knudsen-type vapor transport combined with fluid transport by thermal expansion of the adsorbed water layers in the non evaporated zone, showed the best agreement with experi-mental evidence.
234U/230TH Ratio as an Indicator of Redox State, and U, TH, and RA Behavior in Briney Aquifers
Authors: Laul J. C. , Smith M. R. , Hubbard N. 
Published: March 2011

AbstractThe234U/230Th ratio serves as an in-situ indicator of the redox state in groundwater aquifers. The higher this ratio, the more U there is in the +6 valance state and thus a less reducing environment. Radium sorption is retarded in the shallow aquifer and is dependent on the CaSO4content and the redox state. Relative to Ra, U and Th are highly sorbed. The total retardation factor for Th is ∼1400 and mean sorption time for228Th is ∼10 days in the shallow zone. The desorption rate of Ra is significantly slower in the shallow than in the deep aquifer. There is no effect of colloids in brines.