bluuebunny/crossref_metadata_2025_split huggingface dataset:
Full-Contact Type Linear Image Sensor by Amorphous Silicon
Authors: Hayase Masaki , Arita Hirotaka 
Published: March 2011

ABSTRACTA new type of the contact linear image sensor array using amorphous silicon photodiodes has been developed. The new device, namely “Full Contact” type, linear image sensor, has a pinhole of 60 µm in diameter at the center of the amorphous silicon photodiode pixel. With this structure, the focusing lens can be removed and the optical path can be reduced by about one half as compared with an ordinary facsimile scanner. Eventually the device becomes quite compact in volume and production process are rather simple, result in low cost. LED driven 1728 pixels for A4 size and 2048 pixels for B4 size devices with the resolution of 8 dots/mm have been developed so far. A series of technical data for the development of devices and their operational performance are presented and discussed.
Peak-To-Peak Voltage (Vp-p) on Rf Powered-Electrode and Sensitivity of Amorphous Silicon (A-Si) Photoreceptor
Authors: Yamazaki Toshinori , Kobayashi Nobuaki , Takahashi Satoshi , Nakanishi Tatsuo 
Published: March 2011

ABSTRACTIt has been found that photosensitivity of amorphous silicon (a-Si) photoreceptor fabricated by g1ow-discharge decomposition of SiH4 – B2H6 – Ar has specific relation to peak-to-peak value of Rf (13.5 MHz) voltage (Vp - p) and DC bias voltage (Vdc) on the Rf powered-electrode. The lower the Vp - p value is depressed, the higher the photosensitivity is improved. Dependences of the Vp - p value on deposition parameters such as gas pressure, distance between Rf powered-e1ectrode and aluminum substrate, Rf electric power and dilution ratio of SiH4 to Ar seem to indicate correlation of Vp - p with electron energy and electron density in the plasma.Furthermore, the Vp - p and Vdc values have been measured in plasma of He, Ne (rare-gases with no Ramsauer effect), Ar, Kr, Xe (rare-gases with Ramsauer effect), and H2, N2, CH4, SiH4 (molecular-gases): Specific behaviors in Vp - p and Vdc seem to have correlation with collision cross - sections of electrons (with the energy of 2 ∼ 10 eV) in these gases.
Thin-Film Amorphous Silicon Dynodes for Electron Multiplication
Authors: Tasker G.W. , Horton J.R. , Fijol J.J. 
Published: March 2011

ABSTRACTThe design and fabrication of novel, thin-film continuous dynodes for a new generation of channel electron multipliers (CEMs) and microchannel plates (MCPs) are described. In particular, we demonstrate the feasibility of forming such dynodes by low pressure chemical vapor deposition (LPCVD) of amorphous Si films in capillary channels of macroscopic to microscopic dimensions. Finally, we discuss potential performance advantages of thin-film dynodes over conventional reduced lead silicate glass dynodes for CEMs and MCPs and implications for new applications.
Nucleation and Growth in Vicinity of Growing Surface in Making Microcrystalline Silicon
Authors: Nakata Masami , Namikawa Tatsuru , Shirai Hajime , Hanna Jun-ichi , Shimizu Isamu 
Published: March 2011

ABSTRACTA close study was conducted on microcrystalline Silicon (μc-Si) prepared by PE-CVD (Plasma Enhanced CVD) from SiF4 with the assistance of atomic hydrogen. The atomic hydrogen played a major role in either making precursors, SiFnHm (n+m=3), by gas phase reactions with the fragments, SiFn (≤3), or constructing Si-network in the vicinity of the growing surface. Proper conditions of nucleation were markedly different from those of growth with respect to parameters, flow of atomic hydrogen and substrate temperature.
New Doping Technique for Getting Highly Conductive p-Type Hydrogenated Amorphous Si and Sic Alloys
Authors: Takeuchi Y. , Nomoto K. , Ganguly G. , Matsuda A. 
Published: March 2011

ABSTRACTHighly conductive B-doped hydrogenated amorphous Si (a-Si:H) as well as amorphous SiC alloys (a-SiC:H) have been prepared from (SiH4) / (B2H6/SiH4) and (SiH4/CH4)/(B2H6/SiH4) plasmas, respectively by a novel surface-temperature-modulation method. Films produced by this technique exhibit a higher conductivity as compared to the conventionally prepared films, i.e., 7.0×l0−3scm−l for p-type a-Si:H with an optical gap of 1.7eV and 5.5×l0−5Scm−l for p-type a-SiC:H of optical gap 1.9eV.
Optimization of the Properties of Undoped a-Ge:H
Authors: Turner W. A. , Pang D. , Wetsel A. E. , Jones S. J. , Paul W. , Chen J.H. 
Published: March 2011

ABSTRACTHigh density, non-porous, highly photoconductive films of undoped a-Ge:H showing minimal microstructure have been prepared out of an r.f. glow discharge of GeH4 on substrates mounted on the powered electrode of a diode reactor. These films, prepared under the systematic variation of substrate temperature, discharge power and dilution of the plasma by H2 are markedly different from those produced on the unpowered electrode. An optimum level of applied power is found which does not differ significantly from that used to prepare state-of-the-art a-Si:H. For the reactor geometry used, dilution of the plasma with H2 is found to be essential to the preparation of high quality a-Ge:H. These films contain similar amounts of bound hydrogen to that found in good a-Si:H, and also relatively large quantities of unbound hydrogen. Transport is activated with a Fermi level near mid-gap, the dangling bond spin density is 5 × 1016 spins/cm3, and the samples exhibit photoluminescence. The electron μÄ has been measured using the TOF technique. The conditions for preparation of optimized material are quite different for those found to optimize the preparation of high quality a-Si:H in this reactor. This is asserted to be a principal cause for our finding, along with other laboratories, of inferior properties for a-SiGe:H alloys when compared with those of a-Si:H.
Fabrication of Device-Quality Wide-Gap a-Si:H Films at Very Low Substrate Temperatures
Authors: Hishikawa Yoshihiro , Tsuge Sadaji , Nakamura Noboru , Tsuda Shinya , Nakano Shoichi , Ohnishi Michitoshi , Kuwano Yukinori 
Published: March 2011

ABSTRACTWide-gap a-Si:H films with device quality (Tauc’s optical gap > 1.9eV, σph under AMI.5, 100mW/cm2 illumination ≥ 10−5, Ω−1cm−1, a σph/σ a≥106) have been fabricated. These films are deposited at low substrtate temperatures (TS≤80°C ) either by diluting SiH4 with H2 or optimizing the plasma parameters in a capacitively–coupled RF plasma–CVD reactor. Reduction in the SiH2 bond density and the ESR spin density are also observed. In this study, good film quality is always accompanied by a small deposition rate. Furthermore, σph is nearly the same if the deposition rate and Ts is the same, regardless of other deposition parameters. This suggests that the surface reactions or structural relaxations at the film-growing surface can produce high–quality a–Si:H films even at low TsS, if the deposition rate is low. Results in thermal annealing, light exposure, and solar cell performance confirm that these films have device quality and wide bandgap.
Reduction of Si-H2 Bond Content in Hydrogenated Amorphous Silicon Prepared by Mercury-Sensitized Photochemical Vapor Deposition
Authors: Sakuma N. , Nozaki H. , Niiyama T. , Ito H. 
Published: March 2011

ABSTRACTThe ratio of Si-H2 bonds to hydrogen content in hydrogenated amorphous silicon films, prepared by mercury-sensitized photochemical vapor deposition, depends on the deposition conditions, in particular on the distance between the substrate and the light-transparent window.The ratio is reduced from 20 % to 8 % by decreasing the distance from 30 mm to 8 mm. On the other hand, the hydrogen content remains constant at 15 at.%. Decreasing the distance has been found to be almost equivalent to increasing the light intensity, especially 254 nm-light intensity.
Etching Selectivity of SiF4 and H2 Plasmas for c-Si, a-Si:H and SiO2
Authors: Okada Y. , Wagner S. 
Published: March 2011

ABSTRACTThe etching of a-Si:H, c-Si and SiO2 in glow discharges of SiF4 and H2 was studied. The order of the etch rates in a SiF4 plasma is a-Si:H > c-Si > SiO2. The etch rates of these materials are nearly independent of temperature. Only a-Si:H is etched in a H2 plasma.
Comparison of the Properties of Sputtered and Glow Discharge a-Ge:H Films
Authors: Wetsel A. E. , Jones S. J. , Turner W. A. , Pang D. , Paul W. , El Zawawi I. , Bouizem Y. , Chahed L. , Theye M. L. , Marques F. C. , Chambouleyron I. 
Published: March 2011

ABSTRACTUndoped a-Ge:H films have been made both by sputtering and by glow discharge under various combinations of deposition parameters, and characterized structurally, electrically, and optically. A detailed comparison of subband gap spectra of sputtered and glow discharge samples has been carried out using photothermal deflection spectroscopy and the constant photocurrent method. The results show subband gap absorption in a-Ge:H to be an order of magnitude larger than in device-quality a-Si:H. For some of the films the absorption spectra deduced from transmission and PDS fit very well onto the absorption spectra inferred from CPM measurements, while for others it is clear that the match is very poor. We infer that the photoconductivity-derived spectrum does not necessarily reflect the dominant absorption process, and that this is related to the existence of a two-phase structure clearly observed by transmission and scanning electron microscopy.
The Effect of Sample Substrate on the Structural Properties of Co-Deposited Films of A-Ge:H
Authors: Jones S.J. , Turner W.A. , Pang D. , Paul W. 
Published: March 2011

ABSTRACTResults from structural measurements on r.f. glow discharge produced a-Ge:H films have been found to be substrate dependent. The variations in the results were found to depend on both the substrate temperature, Ts, and the substrate yield strength. Differential scanning calorimetry results were particularly affected by these parameters. For films prepared at Ts = 150°C, the DSC spectra contain two exothermic peaks when the films are deposited on low yield strength substrates while only one exothermic peak is present for films deposited on high yield strength substrates. One exothermic DSC peak is seen in spectra for all films prepared at Ts = 300°C no matter what substrates were used. This DSC spectral dependence is attributed to differences in the microstructure of films deposited at the two substrate temperatures, as seen in TEM micrographs. X-ray diffraction measurements performed on films annealed to various temperatures show that all of the exothermic DSC peaks described above are associated with the crystallization process. Thus, for the films prepared at low Ts, crystallization is either a one or two step process depending on the yield strength of the substrate.
Optimization of a-Ge:H Films
Authors: Eberhardt K. , Schubert M. B. , Eicke A. , Bauer G.H. 
Published: March 2011

ABSTRACTAmorphous hydrogenated germanium films have been deposited in a conventional glow discharge reactor (diode as well as triode configuration) from GeH4 with and without additional H2 dilution. In this study special emphasis was put on samples deposited at different substrate temperatures, different neutral gas densities and dilution ratios. The deposition rate has been varied from 0.2 to 2.5 Å/s. Optical, structural and electronic properties have been studied by VIS/NIR thin film spectroscopy, PDS, Raman backscattering, FTIR, as well as temperature dependent dark and photoconductivity. Hydrogen content was monitored by quantitative SIMS analysis and FTIR spectroscopy.By ‘soft’ deposition, i.e. high pressure and H2 dilution ratio, Fermi level positions near midgap (Eact =0.48eV at Eg=1.0ev) are achieved. Nevertheless the optimum ratio σph/σd is restricted to 0.6 at room temperature (λ=632.8nm). To point out the influence of Fermi level position for transport properties, we investigated two samples with different Fermi level positions in detail. σd(T) is strongly dependent on Fermi level positions, as well as the absolute values of σph(T), whereas the temperature dependence of σph(T) does not differ greatly. This is an indication, that Fermi level position and recombination centers of a-Ge:H can be effectively influenced by changing deposition parameters.
The Influence of Deposition Conditions on the Properties of a-Sic:H Thin Films
Authors: Magafas L. , Girginoudi D. , Georgoulas N. , Thanailakis A. 
Published: March 2011

ABSTRACTThe dependence of chemical composition, structure and optoelectronic properties of sputtered a-SiC:H thin films on substrate temperature, Ts, and hydrogen flow rate has been studied. The films are amorphous for the growth conditions used in this work. The chemical composition of the alloys is very little influenced by the Ts, whereas the hydrogen content and the optical absorption coefficient depends strongly on Ts and hydrogen flow rate.
1.00 Mev Proton Induced Defects in a-Si:H thin Films and Solar Cells
Authors: Payson J. Scott , Abdulaziz Salmam , Li Yang , Woodyard James R. 
Published: March 2011

ABSTRACTIrradiation of thin films and solar cells with 1.00 MeV protons has been investigated for a fluence of 5.0E14 cm−2. We have used photothermal deflection spectroscopy and light conductivity to characterize the effect of irradiation on thin films; current-voltage and quantum efficiency measurements have been used to determine the effects of irradiation on solar cells.Irradiation introduces increases in the sub-band-gap optical absorption and decreases in the photoconductivity of thin films. The major effect on solar cells is to reduce the short-circuit current. The spectral dependence of the quantum efficiency is reduced in a somewhat uniform manner with irradiation and also recovers in a uniform manner with annealing. Investigations of the annealing behavior of both thin films and solar cells show similar behaviors in the measured properties. The properties of both the films and cells are essentially restored with a one-hour anneal at 200 °C. Attempts have been made to use simple models to calculate defect densities and carrier transport.
Trace Impurities and Metastable States in a-Si:H
Authors: Unold Thomas , David Cohen J. 
Published: March 2011

ABSTRACTThe effect of trace amounts of impurities such as carbon and nitrogen on the density of states in undoped a-Si:H has been investigated using drive-level capacitance profiling and transient photocurrent methods. The results indicate a significant correlation between impurity levels and the susceptibility to metastable state creation after light-soaking. We found this correlation to be independent of bandtail broadening and hydrogen content in the material.
The Generation and Bleaching of Positive Charge in Gate-Quality Nitrogen-Rich Amorphous Silicon Nitride By Sub-Bandgap Illumination
Authors: Kanicki J. , Sankaran M. 
Published: March 2011

ABSTRACTWe report, for the first time, on the stretched-exponential time dependence of the generation and bleaching of positive charge in gate-quality nitrogen-rich amorphous silicon nitride films subjected to the sub-bandgap illumination at room temperature in vacuum. We also propose a mechanism which we believe is responsible for the generation and bleaching of the positive charge in the nitride films.
Fluorinated Silicon Nitride (a-Si:N,F,H) Films Using NF3 for Amorphous Silicon Based Solar Cells
Authors: Goh Freddy. H. C. , Tan S. M. , Ng K. , Naseem H. A. , Brown W. D. , Hermann A. M. 
Published: March 2011

ABSTRACTThe large amounts of methane commonly used to prepare wide-gap a-SiC:H films present a lot of problems. This study was aimed at investigating the properties of fluorinated silicon nitride as an alternative to silicon carbide and to study the thermal stability of the films.The RF glow discharge of NF3 (an etchant gas) and pure SiH4 produced a-Si:H,N,F films. Films were deposited with a gas ratio of NF3 over (NF3 + SiH4) from 0% to 15%. The substrate temperature, chamber pressure, and power were kept constant; only flow rate was varied. Characterizations of the films included AES, FTIR, visible/UV spectroscopy, dark conductivity, and photoconductivity.Deposition rate increased about eight times with an addition of 6% NF3. The deposition rate increased from 1.22 A/s to 10.5 A/s. The Tauc optical gap increased from 1.72 eV to about 2.06 eV, suggesting excellent N incorporation. The dark conductivity decreased one order of magnitude while the photoconductivity decreased by as much as five orders of magnitude with ELH light. FTIR spectra showed the nitrogen incorporation. The Si-N bonds replaced the Si-Si bonds with increasing NF3 concentration. Also with increasing NF3 content in the gas phase, the hydrogen concentration in the material decreased and the films became more thermally stable.
Recombination at Dangling-Bonds and Fermi Level Effects on Steady-State Photoconductivity and Light-Induced ESR in a-Si:H
Authors: Morgado E. 
Published: March 2011

ABSTRACTA simple recombination model is proposed in order to explain Fermi level effects on steady-state photoconductivity in a-Si:H. The model assumes positively correlated dangling-bonds as the only localized states in the gap and takes into account the occupation statistics of correlated defect centers in the dark and under illumination. The steady-state photoconductivity and its dependence on the light intensity are investigated as a function of the Fermi level position in the gap. The results show a good agreement with experimental data from undoped, phosphorus and boron doped a-Si:H material. The quenching of the g≈2.0055 Electron Spin Resonance signal upon illumination in undoped samples and its enhancement in doped ones are also reproduced by the model.
Bonding and Electronic Structure of Nb/NbC and Nb/NbSi2 Interface
Authors: Donovan M. M. , Maclaren J. M. , Eberhart M. E. , Barron A. R. 
Published: March 2011

ABSTRACTThe atomic origins of the intrinsic mechanical and thermal properties of the interfaces between niobium and its carbides and silicides are explored using both the layer Korringa-Kohn-Rostoker (LKKR) technique and model cluster calculations. The relative stability of an idealised [100] interface is predicted from charge transfer arguments.
Theoretical Study of High Pressure Metallic Hydrogen
Authors: Barbee Troy W. , García Alberto , Cohen Marvin L. 
Published: March 2011

ABSTRACTA study of the zero temperature phase transitions in hydrogen under megabar pressures using a first-principles total-energy method is presented. An anisotropic primitive hexagonal phase is found to be particularly stable relative to other monatomic phases for pressures between 4 and 8 megabars. Calculations of the vibrational frequencies show that this phase is unstable with respect to a distortion tripling the unit cell along the c-axis. Results for this distorted hexagonal phase will be presented, including a calculation of its superconducting transition temperature Tc.
A Comparison of the Direct Configurational Averaging and Connolly-Williams Methods of Obtaining Effective Pair Interactions in Substitutionally Disordered Alloys
Authors: Wolverton C. , Dreysse H. , Fontaine D. De 
Published: March 2011

ABSTRACTIn order to calculate thermodynamic properties of disordered alloys, it is necessary to extract certain parameters (namely effective cluster interactions) from electronic band structure models. Several of these methods exist, thus necessitating a comparison of their accuracy and convergence. Direct configurational averaging is performed in both a canonical (concentration-dependent) and grand canonical (concentration- independent) scheme. These results are compared with those derived from the Connolly-Williams Method and “exact” results obtained on a simple, tight-binding, d-band model.
Atomic Structure Calculations of the Interaction between Lattice Dislocations and Grain Boundaries
Authors: Pestman B. J. , De Hosson J. Th. M. , Vitek V. , Schapink F. W. 
Published: March 2011

ABSTRACTThe interaction between screw dislocations and [1 1 0] symmetric tilt boundaries is investigated by atomistic calculations. In order to study the differences between fcc and ordered alloys and to study the effect of increasing ordering tendency, many-body potentials representing Cu, Cu3Au and Ni3Al were used. For the ordered alloys, the different possible ordering configurations of the boundaries that were studied are discussed.
Calculation of Free Energy from the Internal-Energy Distribution Function
Authors: Phillpot S. R. , Rickman J. M. 
Published: March 2011

ABSTRACTWe outline a new method for the calculation of free energies from a cumulant analysis of the internal-energy distribution function obtained from a Monte-Carlo simulation. The new methodology is validated by comparing the free energy calculated for a perfect crystal from this approach with the free energy calculated by a temperature integration scheme. By comparing the two methods for an inhomogeneous system containing grain boundaries, we investigate the effects of the local-strain distribution on the free energy; for the superlattice of twist grain boundaries studied here, the effects are found to be small.
GaAs Total Energy Tight Binding Hamiltonians for use in Molecular Dynamics
Authors: Broughton Jeremy , Pederson Mark , Papaconstantopoulos Dimitrios , Singh David 
Published: March 2011

ABSTRACTA self-consistent non-orthogonal semi-empirical tight binding Hamiltonian is proposed for GaAs, or any sp system, which is simple, reliable, transferable, accurate and fast to evaluate. Matrix elements are functions of charges, distances between atoms and simple cosines of angles between s and p-electron densities and interatomic vectors which maintain the simplicity of Slater-Koster parameterizations. The tight binding scheme is fit against a large data base of local density functional derived total energies for systems of differing coordination and geometry. The Hamiltonian fulfills the correct Virial constraint, invokes the physically correct relationship between overlap and kinetic energy matrix elements and defines charges via Mulliken or Löwdin schemes. Such Hamiltonians will allow the reliable simulation of statistical mechanically interesting systems of order hundred or more atoms over physically useful periods of time of order tens to hundreds of thousands of time steps within not unreasonable supercomputer budgets.
Calculation of the Atomic Structure of Grain Boundaries in Metals and Alloys
Authors: Foiles Stephen M. 
Published: March 2011

ABSTRACTThis paper reports two applications of computer simulations based on the embedded atom method to the structure of grain boundaries. First, the equilibrium segregation at symmetric twist grain boundaries in Ni-Cu alloys is computed. These simulations include both compositional rearrangements and atomic displacements. It is found that Cu segregates to the boundary and that the change in composition is confined to a few atomic layers near the boundary. The degree of segregation was found to be greater for Ni-rich alloys and for large angle boundaries. The variation of the concentration within the planes parallel to the boundary for a low angle twist boundary is studied and the variations are correlated with the positions of the boundary dislocations. The second application addresses the possibility of structural disorder in the Σ5(001) twist boundary in Au. These results show that defects corresponding to local motion of the boundary normal to the interface are low in energy. The energetics of these defects are then mapped onto the body-centered-solid-on-solid model of surface roughening. This model predicts that a roughening transition will occur in this grain boundary at 100 K or 500 K depending on the choice of interatomic interactions. The effect of this roughening transition on the x-ray scattering from the boundary is also computed.