bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Defect Structures in 3C-SiC Single Crystals Using Synchrotron White Beam X-ray Topography
Authors: Huang W. , Dudley M. , Fazi C. 
Published: April 2011

AbstractDefect structures in (111) 3C-SiC single crystals, grown using the Baikov technique, have been studied using Synchrotron White Beam X-ray Topography (SWBXT). The major types of defects include complex growth sector boundary structures, double positioning twins, stacking faults on { 111 } planes, inclusions and dislocations (including growth dislocations and partial dislocations bounding stacking faults). Detailed stacking fault and double positioning twin configurations are determined using a combination of Nomarski interference microscopy, SEM and white beam x-ray topography in both transmission and reflection geometries. Possible defect generation phenomena are discussed.
Thermal And Optical Admittance Spectroscopy Studies Of Defects In 15r-Sic
Authors: Smith S. R. , Evwaraye A. O. , Mitchel W. C. 
Published: April 2011

AbstractNitrogen is the common n-type dopant of the various polytypes of silicon carbide. The nitrogen levels in 4H-SiC (at EC-53 meV and EC-100 meV) and in 6H-SiC (at EC-89 meV, EC- 100 meV, and EC-125 meV) have been studied in detail by temperature dependent Hall effect measurements, electron spin resonance (ESR), and thermal admittance spectroscopy. Until now, such detailed studies of the nitrogen levels in 15R-SiC have not been carried out.Lely-grown 15R samples were used in these studies. The net carrier concentrations (ND-NA), determined by room temperature CV measurements, ranged from 1 × 1018 to 3 × 1018 cm−3. The nitrogen levels in 15R-SiC were studied using thermal admittance spectroscopy. Optical admittance spectroscopy (OAdS) was used to study the deeper defects in this polytype. It was found that optical transitions to the conduction band were inhibited in the heavily doped material.
Local-Field and Exchange-Correlation Effects in Optical Spectra of Wide-Band–Gap Semiconductors
Authors: Gavrilenko V. I. , Bechstedt F. 
Published: April 2011

AbstractThe density-functional theory with ab initio pseudopotentials has been used to study the linear optical response of semiconductors. We present results for optical spectra where the effects of the macroscopic local-field and microscopic exchange-correlation interaction are included beyond diagonal and random-phase approximation. Quasiparticle corrections to the single-particle energies have been added in the polarization function. Numerical calculations are performed for the column-IV materials Si, SiC, and diamond as model substances.
Surface Photovoltage Effects in Photoemission from Diamond Surfaces
Authors: Bandis C. , Pate B. B. 
Published: April 2011

AbstractPhotovoltaic effects in ultraviolet photoemission spectroscopy of the in-situ “rehydrogenated”, and reconstructed (111) diamond surfaces are evaluated. We show that photovoltaic charging effects during photoemission studies of the in-situ “re-hydrogenated” (111)-(l×l):H diamond surface are significant at temperatures as high as room temperature. In contrast, experiments on the reconstructed (111 )-(2×l) diamond surface find no photovoltaic charging which suggests that the surface exhibits relatively high conductivity (effectively grounded surface). These results demonstrate that extra care should be taken in determining the Fermi level pinning position relative to the bands at diamond surfaces and interfaces. The assumption that the UPS photoelectron spectra reflect the equilibrium energy band arrangement should be experimentally confirmed in each case, especially when wide band gap materials are involved.
A Novel Device Structure for High Voltage, High Performance Amorphous Silicon Thin-Film Transistors
Authors: Miri A. M. , Gudem P. S. , Chamberlain S. G. , Nathan A. 
Published: April 2011

AbstractConventional high voltage thin-film transistors (HVTFTs) suffer from performance limitations such as low on-current, Vx, shift and large curvature in the linear region of the output characteristics. These limitations are associated with the highly resistive dead region in conventional HVTFT structures. In this paper, we present a novel TFT structure which has a high on-current, improved output characteristics in the linear region, and no Vx shift. The higher on-current and significant improvement in output characteristics allows faster switching. Elimination of the Vx shift leads to more reliable circuit operation. The new structure is based on the conventional low voltage TFT (LVTFT) structure except that it does not suffer from low-voltage breakdown. The low-voltage breakdown of the gate nitride in conventional LVTFTs is perceived to be due to spiking of the drain metallization into the underlying layers which creates regions of very high electric field. In our novel structure, a higher breakdown is achieved by locating the metal contacts away from the gate edge while keeping the necessary drain to gate overlap through a heavily doped microcrystalline layer. Therefore, the new TFT extends the same performance as LVTFTs to high voltage operation. Furthermore, this structure also enhances the yield and reliability by minimizing the common faults in TFTs such as short circuits between gate, source and drain.
A novel technique for in-situ monitoring of crystallinity and temperature during rapid thermal annealing of thin Si/Si-Ge films on quartz/glass
Authors: Subramanian V. , Degertekin F. L. , Dankoski P. , Khuri-Yakub B. T. , Saraswat K. C. 
Published: April 2011

AbstractA novel technique is presented to simultaneously measure temperature and crystallinity insitu during the rapid thermal annealing of thin Si / SiGe films on transparent substrates for active matrix liquid crystal display applications. The technique uses acoustic waves to monitor temperature, by measuring changes in velocity with temperature. The technique enables accurate tracking of crystalline phase transitions along with temperature, since it is independent of emissivity. This provides a methodology for closed-loop control and end-point detection. The experiments on thin amorphous Si on Quartz demonstrate temperature repeatability of 2%. Also, the technique proved sensitive enough to detect the onset of nucleation, as evidenced by TEM.
Properties and Stability of Bismuth Doped Tin Oxide Thin Films Deposited on Various Types of Glass Substrates
Authors: Foglietti V. , Alessandro A. D′ , Galbato A. , Alessandri A. , Beccherelli R. , Campoli F. , Petrocco S. , Wnek M. , Maltese P. 
Published: April 2011

AbstractThis work reports on deposition of transparent semi-insulating tin oxide thin films deposited by spray-pyrolysis over large area glass substrates. The precursors used are based on diluted chloride solutions. Bi-doped high resistivity tin oxide thin films are required in the fabrication process of an analog grey scale ferroelectric liquid crystal matrix display. Various parameters have been optimized in order to achieve good reproducibility and uniformity of the electrical and optical properties. Deposition temperature and the properties of the glass substrates have been found as the most critical variables which affect the deposition rate and the quality of the deposited films. The different substrates used, borosilicates and soda-lime glasses, lead to different electrical properties. A further investigation on the stability of the film properties versus different kind of aging procedures have been conducted. Preliminary results of the operation of the complete display making use of our films are shown.
Emission Characteristics of the Mo-Coated Silicon Tips
Authors: Park Heung-Woo , Ju Byeong-Kwon , Jung Jae-Hoon , Lee Yun-Hi , Park Jung-Ho , Chung In-Jae , Hascard M. R. , Oh Myung-Hwan 
Published: April 2011

AbstractUniform and reproducible silicon tip arrays were fabricated using the reactive ion etching followed by the re-oxidation sharpening. Molybdenum was then coated on the some of the silicon tip array. Current-voltage characteristics and current fluctuations were measured in the high vacuum environment. Field emission currents were proved by the Fowler-Nordheim plot studies.
Properties of Diamond-Like Carbon for Thin Film Microcathodes for Field Emission Displays
Authors: Robertson J , Milne W I 
Published: April 2011

AbstractDiamond-like carbon is a strong candidate for field emission microcathodes for field emission displays because of its low electron affinity and chemical inertness. The field emission properties of various types of diamond-like carbon such as a-C:H and ta-C are reviewed in the framework of a bonding model of their affinity.
Study on the Diamond Field Emitter Fabricated by Transfer Mold Technique
Authors: Ju Byeong-Kwon , Kim Seong-Jin , Jung Jae-Hoon , Lee Yun-Hi , Park Beom Soo , Baik Young-Joon , Lim Sung-Kyoo , Oh Myung Hwan 
Published: April 2011

ABSTRACTStrip-shaped diamond-tip field emitter array was fabricated by using the transfer mold technique. The sharp turn-on characteristic was observed from the current-voltage measurement of the fabricated diamond-tip field emitter array. The turn-on characteristic of the diamond-tip field emitter array was compared with that of a flat diamond film. High emission current density was obtained from the diamond-tip field emitter array. The threshold voltage of the diamond-tip field emitter array was lower than that of a flat diamond film.
Characterization of Low-Voltage Phosphor Screens for Fed Applications
Authors: Jeon B. S. , Kang S. W. , Yoo J. S. , Lee J. D. 
Published: April 2011

ABSTRACTA phosphor screen which operates at low excitation energy must show good emission efficiency and sustain stabilities against high vacuum and high current density operation. In this study, low voltage phosphors suitable for FED applications were experimentally addressed and screened onto ITO-glass by the electrophoretic deposition which offers several advantages, including easy control of film thickness and high packing density. Process variables such as deposition rate, salt concentration, etc., in electrophoretic deposition method were optimized to achieve high quality of the screens. Correlations of process variables with particle size, surface morphology and luminescent properties of phosphors will be presented. Particularly, much attention was put on the optimization of phosphor screens for the maximal CL intensities and adhesion of particles over substrate when excited by field emitter arrays.
a-Si:H TFTs Patterned Using Laser-Printed Toner
Authors: Glesková Helena , Wagner S. , Shen D. S. 
Published: April 2011

AbstractWe fabricated top-gate amorphous silicon thin-film transistors (a-Si:H TFTs) on alkali-free glass foil, for the first time using laser-printed toner for the patterning of each layer. The toner for the first mask level was applied by feeding the glass foil through a laser printer, and for the following mask levels from patterns laser-printed on transfer paper. The transistors have off currents from ˜ 10-12 A to ˜ 10-11 A and on-off current ratios of ˜ 106. Thus we have demonstrated a technology for the patterning of TFT circuits by printing.
Deuterium NMR Spectroscopy of Solvents Adsorbed onto the Surface of Mesoporous Silica
Authors: Attard George S. , Edgar Mark , Emsley James W. , Göltner Christine G. 
Published: April 2011

AbstractA series of simple deuterium NMR experiments are used to investigate the surfaces of differently structured silicas by studying the sorption of deuteriated solvents. Two mesoporous silicas (MCM-41 and H1-silica), which display hexagonally arranged channels of uniform diameter are studied, as well as amorphous column silica. The deuterium NMR lineshape strongly depends on the anisotropic environment of the adsorbed deuteriated species (D2O, benzene-d6, pyridine-d5). This allows differentiation between probe molecules adsorbed to the internal surface (anisotropic) and to the external surface (isotropic, non-ordered surface of particles). Solvents adsorbed within the channels of the silica nanostructure retain a degree of orientational order while moving on the surface, thus producing a Pake pattern. In contrast, solvents adsorbed on the outside of the ordered channels and on domain boundaries retain no orientational order while moving on the surface, therefore giving rise to a singlet in the deuterium NMR spectrum. This phenomenon allows to judge and compare the qualities of hexagonal ceramic nanostructures. The results show that H1-silica exhibits a significantly higher degree of order, due to a larger domain size, than MCM-41.
Low Molar Mass Glassy Chiral Nematic Oligomer With Large Polarization Bandwidth
Authors: Krishnamurthy S. , Kalmanash M. , Sethna V. 
Published: April 2011

AbstractA novel low molar mass glassy chiral nematic oligomer has been developed that exhibits a large selective reflection bandwidth (>100 nm). This has immense potential in applications requiring the polarization of light over a broad spectral bandwidth, corresponding to the range of human vision, with minimal absorption and high efficiency. Definite advantages are observed over other low molar mass and polymeric chiral nematic materials reported in the literature that typically have narrower polarization bandwidths requiring more complex structures to cover the visible spectrum. The glass transition and clearing temperatures of this material are well separated, that in turn facilitates device processing. Devices up to 4"×5" have been successfully fabricated. Their optical properties are discussed.
Uv Curable Liquid Crystals and Their Application
Authors: Takatsu H. , Hasebe H. 
Published: April 2011

AbstractSome classes of liquid crystalline monoacrylates having no methylene spacers in a side chain have been prepared. The liquid crystalline monoacrylates have effects to reduce the driving voltage and the hysteresis for a light scattering display of Polymer Network liquid crystals prepared by photo-polymerization-induced phase separation.By photo-polymerization of a chiral monoacrylate monomer in a nematic liquid crystalline host including a black dichroic dye, a polarizer free reflective Spiral Polymer Aligned Nematic (SPAN) Guest Host (GH) LCD exhibiting a low driving voltage has been fabricated. The effect of the spiral polymers made of some kinds of chiral monoacrylates for a Super Twisted Nematic (STN) LCD using SPAN liquid crystals is discussed.UV-curable liquid crystals showing nematic phases at room temperature have been developed. By in situ photo-polymerization, the UV-curable liquid crystals can be utilized for the retardation film with high quality and good thermal stability. The fabrication of various kinds of retardation film using the UV-curable liquid crystals is discussed.UV-curable liquid crystals having isotropic-nematic-smectic A phase sequence have been developed and the photo-polymerization at the state of their uniaxially oriented smectic A phases at room temperature is discussed. The polymerized film is optically uniaxial and transparent without light scattering.
Side Chain Liquid Crystalline Block Copolymers With Chiral Smectic C* Mesogens
Authors: Zheng Wen Yue , Hammond Paula T. 
Published: April 2011

AbstractA new series of side chain liquid crystalline-amorphous diblock copolymers has been successfully synthesized using chiral mesogens. Anionic polymerization techniques have been used to make these monodisperse diblock materials. Preliminary studies suggest that these microphase segregated diblock copolymers exhibit a smectic C* phase. This mesophase exists between and above the glass transition temperatures of the two polymer blocks. Synthesis and characterization of these novel materials are discussed.
Silicon Parallel Multilayer Thin Film Solar Cells
Authors: Green Martin A. , Sproul Alistair B. , Puzzer Tom , Zheng Guang Fu , Basore Paul , Young Trevor 
Published: April 2011

AbstractA new silicon parallel multilayer solar cell structure has recently been reported which can give high solar cell energy conversion efficiency from low quality silicon material. Advantages of this structure are described as is recent characterization work which compares the properties of grain boundaries in experimental devices to those predicted by earlier calculations.
Advanced, Thin, Polycrystalline Silicon-Film™ Solar Cells on Low-Cost Substrates
Authors: Hall Robert B. , Barnett Allen M. , Cotter Jeff E. , Ford David H. , Ingram Alan E. , Rand James A. 
Published: April 2011

AbstractThin, polycrystalline silicon solar cells have the potential for the realization of a 15%, lowcost photovoltaic product. As a photovoltaic material, polycrystalline material is abundant, benign, and electrically stable. The thin-film polycrystalline silicon solar cell design achieves high efficiency by incorporating techniques to enhance optical absorption, ensure electrical confinement, and minimize bulk recombination currents. AstroPower's approach to a thin-film polycrystalline silicon solar cell technology is based on the Silicon-Film™ process, a continuous sheet manufacturing process for the growth of thin films of polycrystalline silicon on low-cost substrates. A new barrier layer and substrate have been developed for advanced solar cell designs. External gettering with phosphorus has been employed to effect significant improvements leading to effective minority carrier diffusion lengths greater than 250 micrometers in the active silicon layer. Light trapping has been observed in 60-micrometer thick films of silicon grown on the new barrier-coated substrate. An efficiency of 12.2% in a 0.659 cm2 solar cell has been achieved with the advanced structure.
Determination of the Recombination Processes in Copper Ternary Chalcopyrites by Phototransport Measurements
Authors: Lubianmker Y. , Bitton G. , Balberg I. , Resto O. , Weisz S. Z. 
Published: April 2011

AbstractWe have measured the phototransport properties of CuGaSe2 films as a function of temperature. The simplest model which is consistent with all the experimental results consists of two recombination levels, one of which is donor-like and the other is acceptor-like. This model is similar to the symmetrical two-level model, which we have recently suggested for CuInS2 films. We thus conclude that this model, with slight variations, represents the general recombination level structure in all copper ternary chalcopyrites.
Chemical Bath Deposition of CdS Thin Films: Growth and Structural Studies
Authors: Zhu Yuming , Mao Dull , Williamson D. L. , Trefny J. U. 
Published: April 2011

AbstractChemical-bath-deposited CdS thin films from an ammonia-thiourea solution have been studied by x-ray diffraction, surface profilometry, ellipsometry, and other techniques. The compactness of the CdS films, structural properties of the films, and the growth mechanism have been investigated. For the deposition conditions used, we found that the film compactness reaches its maximum at a deposition time of 35 minutes. Films grown at longer deposition times are less compact, consistent with the CdS duplex layer structure proposed previously. This transition from compact layer growth to porous layer growth is important for depositing CdS films in solar cell applications. Based on x-ray diffraction (XRD) studies, we were able to determine the crystal phase, lattice constant, and other structural properties.
The Stability Improvement of a-Si:H Films for Photovoltaic Applications
Authors: Budaguan B. G. , Aivazov A. A. , Meytin M. N. 
Published: April 2011

AbstractThe origin of metastability in a-Si:H films deposited at different deposition conditions has been investigated by joint analysis of light-induced defect generation kinetics (Staebler-Wronski Effect) and differential scanning calorimetry (DSC) measurements. Light-induced defect generation kinetics were measured at elevated temperatures of 80–150 °C. DSC measurements were performed in a temperature range of 20 °C – 570°C. The films microstructure were studied by IR spectroscopy analysis.The simulation of DSC curves has been used to deduce the kinetics of the low-temperature exothermic peak (LTEP) observed at 80–150°C. It was found that kinetic parameters of LTEP and SW effects has the same dependence on microstructure parameters, γ, which suggests their common nature. The analysis of a-Si:H stability improvement concerning the influence of films microstructure on the kinetics of relaxation processes is presented.
A Search for Degradation Mechanisms of CdTe/CdS Solar Cells
Authors: Meyers P. V. , Asher S. , Al-Jassim M. M 
Published: April 2011

AbstractCdTe/CdS solar cells have demonstrated stability over thousands of hours of field testing, but have not yet established the same track record for reliability achieved by crystalline Si PV modules. In order to identify potential degradation mechanisms, this paper describes a series of experiments in which CdTe/CdS solar cells are subjected to combinations of temperature, voltage and illumination levels intended to stress the devices beyond levels which would be experienced in the field. During this process the devices display decreases in Voc and FF which are tentatively attributed to chemical changes at the low resistance contact to the CdTe and to changes in the electrical transport properties of the CdTe. Two thermally activated effects were observed depending upon stress bias. Reverse bias appears to degrade bulk CdTe electrical properties while forward bias strengthens a reverse diode which most likely is located at the back contact. Chemical analysis of the back contact region of the devices using XPS reveals strong oxide peaks in all stressed samples. Evidence of Cd diffusion into the Mo contacts is observed by SIMS and Auger. Mo diffusion into the CdTe is promoted by reverse bias stressing. Cu migration consistent with positively charged ions was indicated by SIMS.
Structural Characterization and Electrical Conductivity Percolation in (CdTe)1-x Tex
Authors: Morella G. , Katiyarb R. S. , Espinoza-Beltrán F. , Ramirez-Bon R. , Zelaya-Angel O. 
Published: April 2011

AbstractSamples of the (CdTe)1-xTex diphasic system were grown by HWFE on glass plates kept at temperatures between 150 and 260 °C. The films have excess elemental tellurium varying between 12 and 67 vol%. X-ray analyses showed the samples to be diphasic with CdTe in the cubic phase and Te in the hexagonal phase. The excess tellurium concentration increased as the substrate temperature diminished. The critical volume fraction for conductivity percolation in the (CdTe)1-xTex system was determined to be around 0.4, which indicates a non-random distribution of the excess Te. Raman spectroscopy was used to characterize the Te phase across the conductivity percolation threshold. The integrated intensity of the first-order A1 mode increases dramatically at the percolation transition. Second-order Raman scattering from Te is also seen, but only for those samples with over 38 vol% Te. In addition, the A1 mode is shifted to higher energies in films with concentrations below the transition point, revealing that Te goes from a state of tensile stress into a relaxed state as the films pass from low to high conductivity. These results indicate that simultaneously with the Te network connectivity there occurs aggregation of the excess Te, which was initially located at the grain surfaces. This mechanism relieves the strain and gives rise to high conductivity and extended vibrational modes resembling those of bulk elemental tellurium at volume concentrations around 40% and above.