bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon and Oxide Coatings on Continuous Ceramic Fibers
Authors: Hay R. S. , Petry M. D. , Keller K. A. , Cinibulk M. K. , Welch J. R. 
Published: April 2011

ABSTRACTOxide - carbon multilayer coatings were continuously applied to various fibers of nominal SiC composition. A liquid-phase coating system that allows application of the coatings in a controlled atmosphere at relatively rapid rates was employed. Sugar - ammonium hydroxide solutions were used for carbon coatings, and aqueous sols were used for the oxides. Carbon was also deposited simultaneously with alumina by chemical vapor deposition of a hydrocarbon in the coating furnace. The coatings were extensively characterized by optical microscopy and TEM. Problems with embrittlement by oxide coatings and poor adherence of oxide coatings on carbon, and some possible solutions to these problems, are discussed.
Structural Criteria for Amorphization of Network Solids
Authors: Sreeram A. N. , Hobbs L. W. 
Published: April 2011

AbstractAmorphization, like glass-formation, represents fundamentally a failure to crystallize. The problem is to understand how atoms can rearrange themselves, perhaps within the confines of unaffected surrounding crystal, after a local disordering event. Some ceramics, like alkali halides and oxides with the rocksalt structure, appear almost impossible to amorphize, forming localized aggregate defects (voids, dislocation loops, colloids) and even decomposing (as a response to radiation disorder), rather than structurally reordering (or disordering). Other network solids such as silicas and silicates readily amorphize. In this study, we attempt to establish topology and structural freedom as criteria for amorphization of network solids.
Raman and Cathodoluminescence Study of Electron Irradiated Bssco and Ybco Ceramics
Authors: Torres A. , Jimenezi J. , Gomez P. , Piqueras J. 
Published: April 2011

AbstractElectron irradiation damage induced in high Tc superconducing ceramics is studied using microRaman and cathodoluminescence. The formation of extended impurity phases is dominant in BSCCO, while oxygen loss and disorder is the main effect observed in YBCO, in this case the local oxygen loss is quantified.
Suppression of Self-Interstitials in Silicon During on Implantation via in-situ Photoexcitation
Authors: Ravi J. , Erokhin Yu. , Christensen K. , Rozgonyi G. A. , Patnaik B. K. , White C. W. 
Published: April 2011

AbstractThe influence of in-situ photoexcitation during low temperature implantation on selfinterstitial agglomeration following annaealing has been investigated using transmission electron microscopy (TEM). A reduction in the level of as-implanted damage determined by RBS and TEM occurs athermally during 150 keV self-ion implantation. The damage reduction following a 300°C anneal suggests that it is mostly divacancy related. Subsequent thermal annealing at 800°C resulted in the formation of 13111 rod like defects or dislocation loops for samples with and without in-situ photoexcitation, respectively. Estimation of the number of self-interstitials bound by these defects in the sample without in-situ photoexcitation corresponds to the implanted dose; whereas for the insitu photoexcitation sample a suppression of ≈2 orders in magnitude is found. The kinetics of the athermal annealing process are discussed within the framework of either a recombination enhanced defect reaction mechanism, or a charge state enhanced defect migration and Coulomb interaction.
Microstructure of Irradiated Silicon
Authors: Williams J. S. , Wong-Leung J. , Goldberg R. D. , Petravic M. 
Published: April 2011

AbstractThis paper provides a brief overview of some issues relating to the microstructure of irradiated silicon which are of importance to the semiconductor industry. The nature of ion-induced disorder and conditions for amorphization are initially treated since the starting microstructure can strongly influence subsequent annealing behaviour, particularly removal of residual defects, dopant diffusion and electrical activation. The use of implantation-induced disorder as a means of removing metallic impurities, so called gettering, is also an issue of major current interest for improved performance of devices. Some new gettering results are discussed.
Void Swelling Resistance in Fe-Cr Alloys at 200 DPA
Authors: Gelles D. S. 
Published: April 2011

AbstractMicrostructural examinations have been performed on a series of binary Fe-Cr alloys irradiated to 200 dpa at 425°C in a fast breeder reactor. The alloy compositions rangedfrom 3% to 18% Cr in 3% Cr increments, and the irradiation temperature corresponded to the peak swelling condition for this alloy class. Density measurements showed swelling levels as high as 7.4%, with the highest swelling found in the Fe-9Cr and Fe-6Cr alloys. Microstructural examinations revealed that the highest swelling conditions contained welldeveloped voids, often as large as 100 nm, and a dislocation network comprised of both a2 <111> and <100> Burgers vectors. Swelling was lower in the other alloys, and the swelling reduction could be correlated with increased precipitation. These results are considered in light of the current theories for low swelling in ferritic alloys, but no theory is available to completely explain the results.
Z-Scan Measurements on Molten Diphenylbutadiene in the Isotropic Liquid State
Authors: Fleitz P. A. , Sutherland R. L. , Bunning T. J. 
Published: April 2011

AbstractThe two-photon absorption cross-section for diphenylbutadiene heated to the isotropic liquid state has been measured using the Z-scan technique. In this experiment, the solid diphenylbutadiene was heated using a temperature controlled hot stage above its melting point. Z-scan measurements using 35ps laser pulses at 532nm were then carried out on molten diphenylbutadiene. The value of the two-photon absorption cross-section at 532nm was measured to be σ2 = (38±8) × 10−50cm4s/photon-molecule. This value corresponds well with the cross-section measured previously for diphenylbutadiene dissolved in chloroform using the degenerate four-wave mixing technique.
Doped Gels for Optical Limiting Applications.
Authors: Brunel Marc , Canva Michael , Brun Alain , Chaput Frédéric , Malier Laurent , Boilot Jean-Pierre 
Published: April 2011

AbstractAluminophthalocyanine and fullerene were trapped in solid transparent matrices using the sol-gel process. The covalent bonding to the matrix improved the chemical stability of the fullerene doped sample. Solid state optical limiting at 532 nm, mainly due to reverse saturable absorption processes, was observed with such samples. The non-linear transmission threshold was typically about 10 mJ/cm2 and an induced density of 1.6 was observed with three orders of magnitude greater illumination. Fluorescent decay measurements support the choice of a three energy level absorption model for the process, which allows indirect measurement of the excited-state absorption.
Towards Magnetic Liquid Crystals
Authors: Patel M. K. , Huang Jianping , Kaszynski Piotr 
Published: April 2011

AbstractA series of new sulfur-nitrogen ring systems with a neutral radical center were designed for incorporation into liquid crystal molecules and formation of discotic and calamitic phases. It is expected that these materials will display unusual magnetic properties associated with partially oriented bulk liquid crystal structures. Synthetic progress toward new radicals and the first discogen with nr-delocalized neutral radical is described.
Optical Limiting in Chromophore-Doped Gelatin Thin Films
Authors: Cooper Thomas M. , Campbell Angela L. , Su Weijie , Obermeier Keith , Natarajan Karthik , Crane Robert L. , Adams W. W. , Brant Mark 
Published: April 2011

AbstractTo develop optical power limiting thin films prepared from water-soluble materials, we have prepared chromophore-doped gelatin thin films. Thin films of gelatin were prepared by spin coating followed by annealing. We also prepared thin films doped with the water-soluble chromophore copper phthalocyanine sodium tetrasulfonate. The films were characterized by film profilometry and optical absorption spectroscopy. Optical power limiting measurements of these films, as well as comparisons with aqueous solution and gels were performed.
Fast Deposition of Polycrystalline Silicon Films by Hot-Wire CVD
Authors: Middya A. R. , Lloret A. , Perrin J. , Huc J. , Moncel J. L. , Parey J. Y. , Rose G. 
Published: April 2011

ABSTRACTPolycrystalline silicon thin films have been deposited at fast growth rates (50 Å/s) by hotwire chemical vapour deposition (HW-CVD) from SiH4/H2 gas mixtures at low substrate temperature (400–500°C). The surface morphology of these films consists of 0.5 – 2.0μm dendritic grains as seen by electron microscopy. The films have a columnar morphology with grains starting from the substrate either on glass or c-Si. Even the 150 nm thick initial layer is polycrystalline. The preferential crystalline orientation of the poly-Si film is apparently not governed by the radiative source but strongly depends on the type and orientation of the substrate. A strong hydrogen dilution (>90%) of silane is essential to obtain poly-Si films with optimal crystalline structure.
Relation Between Defect Density and Local Structures of a-Si:H
Authors: Azuma M. , Nakamura K. , Yokoi T. , Yoshino K. , Shimizu I. 
Published: April 2011

ABSTRACTHigh quality a-Si:H thin films with varied optical gaps in the range from 1.55 to 2.1 eV were fabricated by various methods, i.e., the standard RF glow discharge of silane, “Chemical Annealing” and ECR-H-plasma from SiCl2H2 under in situ monitoring with an ellipsome try. Despite marked differences in the local structure, all these films showed low defect density as low as (3–5) × 1015 cm3. In addition, the stability for light soaking was improved markedly for the films made by promoting intensively structural relaxation with atomic hydrogen.
Power Feeding in Large Area PECVD of Amorphous Silicon
Authors: Kuske J. , Stephan U. , Steinke O. , Röhlecke S. 
Published: April 2011

ABSTRACTPlasma processes are usually worked out in a small-scale environment (electrode area maximum 121 cm2, rf- and VHF- excitation frequencies). In order to meet the requirements of large area device applications they have to be upscaled. The investigations of glow discharge systems for different PECVD reactors (parallel plate- and coaxial electrodes) have shown, that the reactor design (power supply, line connection) sharply influences the large area deposition process. The voltage distribution on the driven electrode especially determines the uniformity of the deposited layer thickness. Possibilities which influence the voltage distribution on large areas will be discussed. The results of large area electrode description as an electrical line will be discussed in comparison with different reactor configurations and the optimization of the behavior of the deposition process. The experimental results of a coaxial reactor (electrode area 5000 cm2, substrate length 120 cm) show that a homogenous deposition of amorphous silicon (layer uniformity of thickness over the length better ± 7 %) by connecting the driven electrode with additional electrical devices is possible.
Monte Carlo Simulations of Defect Relaxation in Amorphous Silicon
Authors: Unold Thomas , Branz Howard M. 
Published: April 2011

ABSTRACTThe structural memory model of slow defect relaxation in a-Si:H is extended to the limit of long defect filling times. The model was proposed in order to explain unusual, defect filling-time dependent capacitance transients that were observed for short defect filling times. For long defect filling pulses however, the experiments show normal charge emission transients that saturate into filling-time independent transients. We present two possibilities for explaining the approach to saturation within the structural memory model. Results of Monte Carlo simulations of the models are discussed.
Recovery Process of Light-Induced Spins in Hydrogenated Amorphous Silicon-Nitrogen Alloy Films
Authors: Zhang Jinyan , Zhang Qing , Kumeda Minoru , Shimizu Tatsuo 
Published: April 2011

ABSTRACTThe influences of sub-gap illumination and thermal annealing on the light-induced neutral dangling bonds (DB's) created in the fast process (FDB's) and those created in the slow process (SDB's) are prominently different in Si-rich a-Si1-xNx:H. The results of photobleaching show that the sub-gap illumination annihilates FDB's, more effectively at 77 K, whereas it appears not to affect SDB's, suggesting that FDB's are produced by a carrier capture at preexisting charged DB's. The annealing behaviors for both FDB's and SDB's are in agreement with the monomolecular kinetics. The attempt-to-anneal frequency, ν0, is ∼ 103 Hz for FDB's and ∼ 107 Hz for SDB's. Annealing-time dependence of the density of light-induced spins at various annealing temperatures can be fit with a distribution of annealing activation energies. In addition, clearly separated peaks of the distribution of annealing activation energies related to FDB's and SDB's are observed. A comparison indicates that SDB's have a nature similar to the light-induced metastable spins in a-Si:H, which are likely to be produced by a creation of new defects.
Carrier-Induced Changes in The Gap States of Undoped a-Si:H Films
Authors: Chen Y. E. , Tsai J. W. , Cheng H. C. 
Published: April 2011

ABSTRACTCarrier-induced changes in the gap states of plasma-enhanced-chemical-vapor-deposited (PECVD) undoped a-Si:H films are systematically studied using isothermal capacitance transient spectroscopy (ICTS) method via the novel structure we proposed previously. The density-of-state distribution g (E) and the energy dependence of electron-capture cross section σn (E) of gap states in undoped a-Si:H films before and after injection of electrons are directly measured for the first time. Experimental results show that the density of g (E) increases but the σn (E) has no obvious change after the electron injection. These indicate that the defects created during the electron injection are the same in type as those of the as-deposited films. In addition, it is found the shape of g (E) distorts after the injection, implying that the gap states with different energy levels are associated with distinct types of defects.
Microwave Glow-Discharge Deposition of Amorphous Silicon Based Alloys at High Deposition Rates for Solar Cell Application
Authors: Guha S. , Xu X. , Yang J. , Banerjee A. 
Published: April 2011

ABSTRACTThe optimum deposition conditions for growth of amorphous silicon (a-Si:H) and silicon-germanium (a-SiGe:H) alloys deposited at high rates using microwave glow-discharge are found to be quite different from those for radio-frequency glow-discharge material deposited at low rates. High substrate temperature (350 to 500 °C), low pressure (1–5 mtorr) and positive ion bombardment are found to be desirable for optimum growth conditions at high deposition rates. We have achieved an active-area efficiency of 11.44% for a double-junction structure in which the bottom cell incorporates a-SiGe:H alloy deposited at 100 Å/sec using microwave glow-discharge.
Performance of Photo-Transistors with thin (50 nm.) a-Si:H Layers
Authors: GadelRab Serag M. , Chamberlain Savvas G. 
Published: April 2011

ABSTRACTPhoto-transistor based a-Si:H image sensors allow the integration of photo-elements and pixel circuitry using standard TFT fabrication processes. While pixel circuitry use thin a-Si:H films (≈ 0.05μm) to minimize the contact resistance, photo-transistors require thick a-Si:H films (≈0.5μm) to maximize photo-sensitivity. We fabricated a new, high sensitivity photo-transistor structure using 0.05μ a-Si:H films. High optical sensitivity is achieved by separating the conduction paths of photo-generated electrons and holes using a secondary gate. Further, the optical path within the photo-transistor is doubled through manipulation of device layout. The photo-transistor show an Ilight/Idarkratio in excess of 103.We compared the transient behavior of conventional and high-sensitivity photo-transistors. We found that both devices display an increase in current with time when biased in either the dark or illuminated conditions. The current increases by six orders of magnitudes then saturates within 200 seconds of bias application. Experiments indicate that this transient behavior is due to a rise in the conductivity of the gap region with time; measurements on 0.05μm thick photo-resistor structures showed that their current increases with time. The shape and temporal range of this behavior rules out the presence of parasitic capacitive effects.
Temperature and Frequency Dependent Characteristics of Amorphous Silicon thin film Transistors
Authors: Slade H. C. , Shur M. S. , Hack M. 
Published: April 2011

ABSTRACTOn the basis of our experimental studies of the temperature dependence of amorphous silicon thin film transistor current-voltage and capacitance-voltage characteristics, we have developed an analytical device model suitable for implementation in circuit simulators. This model describes the above-threshold (on) current and the subthreshold (off) current [1]. In addition, the model is able to incorporate changes in the distribution of localized states which arise from thermal and/or bias stress. In this paper, we identify the temperature-dependent parameters, which describe the temperature dependence of both the on and off currents, and we model the leakage current at large negative gate biases. The modeling results are in good agreement with our experimental data. We also discuss capacitance-voltage characteristics of amorphous silicon thin film transistors for varying gate lengths, temperatures, and frequencies. The measured capacitance-voltage characteristics show strong frequency dispersion, which is related to the trap-limited transport of carriers in the channel. The characteristic time constant, which determines when the channel capacitance becomes dependent on frequency, is on the order of the transit time calculated with the field-effect mobility and the electric field. The field-effect mobility takes into account carrier trapping by the localized states and is a function of gate voltage and temperature.
Utilization of Photoconductive Gain in a-Si:H Devices for Radiation Detection
Authors: Lee H. K. , Drewery J. S. , Hone W. S. , Jing T. , Kaplan S. N. , Perez-Mendez V. 
Published: April 2011

ABSTRACTThe photoconductive gain mechanism in a-Si:H was investigated in connection with applications to radiation detection. Various device types such as p-i-n, n-i-n and n-i-p-i-n structures were fabricated and tested. Photoconductive gain was measured in two time scales: one for short pulses of visible light (< 1 μsec) which simulates the transit of an energetic charged particle, and the other for rather long pulses of light (1 msec) which simulates x-ray exposure in medical imaging. We used two definitions of photoconductive gain: current gain and charge gain which is an integration of the current gain. We found typical charge gains of 3 ∼ 9 for short pulses and a few hundred for long pulses at a dark current level of 10 mA/cm2. Various gain results are discussed in terms of the device structure, applied bias and dark current.
Hyperacuity Image Sensors
Authors: Biegelsen David K. , Jackson Warren B. , Lujan René , Jared David , Weisfield Richard L. 
Published: April 2011

ABSTRACTThe human visual system perceives much smaller spatial steps in edges between high contrast regions than equivalents fine, periodic features. This characteristic is known as hyperacuity. We have designed, simulated, fabricated and characterized amorphous silicon sensors which provide hyperacuity information. The individual pixels are position sensitive detectors, the outputs of which provide the x and y first moments of the cell illumination pattern as well as the average gray level. In the simplest case the top electrode of a standard p-i-n diode sensor is replaced by four edge strip electrodes. Both quadrilateral cells (having all four lateral electrodes on the same side of the p-i-n diode) and duolateral cells (having x-electrodes on top and y-electrodes on bottom) have been tested. Results of probing the cells with rastered spots show that both types provide usable linearity and sensitivity. The duolateral structure provides greater orthogonality of the x and y information. One μm spatial resolution can be achieved with devices compatible with standard amorphous silicon sensor processing.
Numerical Simulation of Point Defect Distributions in a Growing Czochralski Silicon Crystal in Response to an Abrupt Change in the Growth Conditions
Authors: Wijaranakula W. , Zhang Q. S. , Takano K. , Yamagishi H. 
Published: April 2011

AbstractNumerical simulation of point defect distributions in a growing Czochralski silicon crystal with an abrupt change in the crystal growth rate from 1.0 to 0.4 mm/min was performed. The result was fitted to the experimental data for the flow pattern defects obtained from a crystal grown under simulated conditions. From the simulation result, it was observed that the axial temperature distribution shifts slightly upwards as a result of the growth rate reduction. Based upon the argument that the flow pattern defects are of vacancy-type, it is proposed that the generation rate of the flow pattern defects during crystal growth can be described by the classical nucleation rate theory proposed by Becker [Proc.Phys.Soc., 52, 71(1940)]. In addition, it is suggested that the vacancy concentration in the flow pattern defects depends upon the reaction time between the silicon interstitials and the flow pattern defects and thus the crystal growth rate.
Intentional Defect Incorporation in Metalorganic Vapor Phase Epitaxy Indium Gallium Arsenide by Oxygen Doping
Authors: Huang J. W. , Kuech T. F. 
Published: April 2011

AbstractIntentional defect incorporation in metalorganic vapor phase epitaxy (MOVPE) InxGai-xAs was achieved by controlled oxygen doping using diethylaluminum ethoxide (DEALO). DEALO doping has led to the incorporation of Al and O, and the compensation of shallow Si donors in InxGai-xAs:Si with 0≤x≤ 0.25. DLTS analysis on a series of InxGa1-xAs:Si:O samples with 0≤x≤ 0.18 showed that oxygen incorporation led to a set of deep levels, similar to those found in DEALO doped GaAs. The characteristic deep levels appear to remain at a relatively constant energy with respect to the valence band.
Effect of P-Doping Level-POCl3 Diffused or Spin-On Deposited-On the Gettering Efficiency of Polycrystalline Silicon After RTA or CTA
Authors: Loghmarti M. , Mahfoud K. , Muller J. C. , Sayah D. , Siffert P. 
Published: April 2011

AbstractLarge grain polycrystalline silicon wafers have been subjected to post-thermal annealing after a POCl3 pre-diffusion or after a phosphorus doped silica-film deposition (1019p/cm3- 2.1021p/cm3). The different doping levels are obtained by a dilution of the P-doped SOG (2.1021 at/cm3) in a undoped SOG solution .For the first time we have achieved the maximum of the gettering efficiency after post-thermal annealing. The best combination of post thermal cycle parameters and doping level improves the minority carrier diffusion length of quite (300% to 400%) for POCl3 pre-diffused samples and (200% to 275%) for spin-on P-doped (P-SOG) polycrystalline silicon.