bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strain measurement in metallic glasses and metallic-glass-matrix composites by means of x-ray scattering
Authors: Hufnagel Todd , Ott Ryan T. , Almer Jon 
Published: April 2011

AbstractThe availability of high-energy synchrotron beamlines has made it possible to study the development of elastic strain in crystalline phases in metallic-glass-matrix compositesin situduring loading, and to measure elastic strain in amorphous materials as well. In this paper, we discuss experimental techniques and data analysis for these measurements and give examples. We show that the strain in both the amorphous and crystalline phases in a metallic-glass-matrix composite can be extracted from a single scattering pattern.
Rate Sensitivity and Size Effects in Plasma-Enhanced Chemical Vapor Deposited Silicon Oxide Films
Authors: Cao Zhiqiang , Zhang Xin 
Published: April 2011

AbstractPlasma-enhanced chemical vapor deposited (PECVD) silicon oxide (SiOx) thin films have been widely used in MEMS to form electrical and mechanical components. In this paper, both the time-independent and the time-dependent plastic responses of the PECVD SiOx films were studied by the instrumented nanoindentation experiments. Our experiments found an enhanced rate-sensitivity and size-effect in the plastic responses of the PECVD SiOx thin films. In addition, the plastic flow behavior is more homogeneous compared with most inorganic glasses and many metallic glasses. The deformation mechanism in the PECVD SiOx thin films is depicted by the shear transformation zone (STZ) based amorphous plasticity theory. The physical origin of the STZ is elucidated and linked with the plastic deformation dynamics.
High Electron Mobility W-doped In2O3 Thin Films
Authors: Newhouse Paul F. , Park Cheol-Hee , Keszler Douglas A. , Tate Janet , Nyholm Peter S. 
Published: April 2011

AbstractHigh electron mobility thin films of In2−xWxO3+d (0 ≤ × ≤ 0.075) were prepared by pulsed laser deposition. The highest mobility polycrystalline and textured films show mobility >110 cm2/Vs on both amorphous SiO2 and single crystal yttria-stabilized zirconia substrates. The carrier density is in the range 1−3 × 1020 cm−3 at room temperature. The W dopant concentration for films with optimized electrical properties was x ∼ 0.03.
Reliable semi-transparent pentacene thin-film transistors with polymer gate dielectric layers cured at an optimum temperature
Authors: Hwang Do Kyung , Park Ji Hoon , Choi Jeong Min , Lee Jiyoul , Jeong Seong Hun , Kim Eugene , Kim Jae Hoon , Im Seongil 
Published: April 2011

AbstractWe report on the insulator-charging-effects of poly-4-vinylphenol (PVP) gate dielectric on the reliabilities of pentacene thin-film transistors (TFTs). Our PVP films were prepared by spin coating and curing at various temperatures (155, 175, and 200 °C). Evaluated using Au/PVP/p+−Si structures, the dielectric strength of PVP films cured at 175 °C was superior to those of the other PVP films cured at different temperatures. Although saturation current and field mobility (∼0.13 cm2/Vs) obtained from a TFT with PVP film cured at 200 °C appeared higher than those (∼0.07 cm2/Vs) from the device with 175 °C-cured polymer film, the TFT prepared at 200 °C revealed a low on/off current ratio of less than 104 due to its high off-state current and also unreliable saturation behavior under repetitive gate voltage sweep. The unreliable behavior is due to the dielectric-charging caused by gate-electron-injection. We thus conclude that there are some optimal PVP-curing conditions to improve the reliability of pentacene TFT.
Development of a low energy Ne atom scattering system for insulator surface strctural analysis
Authors: Umezawa Kenji , Narihiro E , Oda K , Nakanishi Shigemitsu , Gibson Walter M 
Published: April 2011

AbstractWe have been developing a low energy Ne atom scattering system combined with a time-of-flight spectrometer for insulator surface structural analysis. Insulator surface structure is difficult to study because of charging effects during electron or ion beam bombardment. Structural analyses of insulator surfaces are very important in fundamental research as well as technology fields. In our system, charged ion beams of 2 keV-Ne+ are converted into neutral beams by charge exchange with the same element gas after the primary beam passes through a chopper. Other features of this system are pulsed beams, time-of-flight measurements, and a micochannel plate (MCP) detector is coaxially mounted along the primary beam. This is a home made equipment. We will show the detection systems, as well.
Ion beam modification of polyimides with linear ion source
Authors: Yamaguchi Tetsuro , Hsiao Shih Hsiu , Tanaka Yoshikazu , Ide Ektessabi Ari 
Published: April 2011

AbstractPolyimide films are widely used in various industrial fields. Some typical products are flexible printed circuits (FPCs), flexible displays, and electronic papers. Good adhesion between metal thin films and polyimide films is required for their long lifetime. Ion beam irradiation to the polyimide films modifies the chemical compositions, the chemical states, and the surface nanomorphology. These modifications are potential techniques to improve the adhesion. In this study, the authors employed a linear ion source, which is able to irradiate ion beam on large surfaces homogeneously. The linear ion source is desirable for industrial usage because of its high productivity. The aim of this work was to investigate the effect of modification using the linear ion source. The chemical states of the interface were characterized using x-ray photoelectron spectroscopy (XPS). The surface nanomorphology was investigated by atomic force microscopy (AFM). The performance of the modification system will be discussed, and the characteristics of the modified polyimide will be investigated in detail.
NSF NSDL Materials Digital Library & MSE Education
Authors: Bartolo Laura M. , Glotzer Sharon C. , Lowe Cathy S , Powell Adam C. , Rajan Krishna , Sadoway Donald R. , Warren James A. , Tewary Vinod K. 
Published: April 2011

AbstractThe National Science Foundation created the National Science Digital Library (NSDL) in order to establish a technical, communal, and organizational framework for access to high quality resources and tools that support innovations in teaching and learning at all levels of science, technology, engineering, and mathematics education. As part of the NSDL, the Materials Digital Library (MatDL) Pathway focuses specifically on serving the materials science (MS) community with a target audience that includes MS undergraduate and graduate students, educators, and researchers. MatDL is a collaborative effort involving the Materials Science and Engineering Laboratory at the National Institute of Standards and Technology, Kent State University, Massachusetts Institute of Technology, University of Michigan, Iowa State University, and Purdue University. Our network of collaborations also includes a Nanoscience Interdisciplinary Research Team, Materials Research Science and Engineering Center, and International Materials Institute. A primary goal of MatDL is to bring materials science research and education closer together. MatDL provides innovative uses of digital libraries and the web as educational media in the MS community with particular emphasis on providing: 1) tools to describe, manage, exchange, archive, and disseminate scientific data 2) workspace for open access development of modeling and simulation tools 3) services and content for virtual labs in large undergraduate introductory science courses, and 4) workspace for collaborative development of core undergraduate MS teaching resources for emerging areas. This paper will provide an overview of the NSDL MatDL Pathway, details about specific aspects of the project, as well as interactions between research and education.
The Future of Materials Undergraduate Programs: Can we Avoid Extinction?
Authors: Vanasupa Linda 
Published: April 2011

AbstractIn materials research, the current funding focus has shifted from largely mechanical-properties based aspects of materials to their molecular-level chemical nature, such as biomaterials or nanoscale phenomenon. Along with this shift in emphasis, we have seen many undergraduate materials programs become absorbed by other programs as a concentration in other engineering majors. Many programs have absolved departments in favor of a model where faculty from a variety of departments have adjunct appointments in, say, an interdisciplinary materials science and engineering program. What exactly is the fate of undergraduate materials programs? Is it time for materials science and engineering undergraduate programs to be absorbed into the sea of interdisciplinarity? In this talk, I will present data on the landscape of trends within the undergraduate materials community against the changes in the global arena. What is our role as materials science and engineering educators in the societal state of flux that we face? What are the opportunities? In an attempt to see into the future, we will consider all these questions.
Simulation of Realistic Core-shell Silicon Nanowires
Authors: Biswas Rana , Pan Bicai 
Published: April 2011

AbstractWe have developed an efficient scheme for simulating silicon nanowires with crystalline cores and amorphous sheaths, using molecular dynamics. By starting with a crystalline nanowire and performing high temperature anneal an amorphous outer sheath can be grown with controlled thickness on the nanowire. Simulations for [001] nanowires with diameters of 12 nm find low energy facets between the amorphous and crystalline layers. Simulations for [110] nanowires find weak faceting and an inhomogeneous amorphous-crystalline boundary.
Metastability in Hydrogenated Nanocrystalline Silicon Solar Cells
Authors: Yue Guozhen , Yan Baojie , Ganguly Gautam , Yang Jeffrey , Guha Subhendu 
Published: April 2011

AbstractWe have recently reported that hydrogenated nanocrystalline silicon (nc-Si:H) solar cells exhibit metastability behavior that is significantly different from hydrogenated amorphous silicon (a-Si:H) solar cells. First, we studied the light-induced change of nc-Si:H cells under different light spectra, and observed that no light-induced degradation occurs when the photon energy is lower than the bandgap of a-Si:H, while light-induced degradation indeed occurs when the photon energy is higher than the bandgap of a-Si:H. Based on this observation, we conclude that the light-induced defect generation occurs mainly in the amorphous and/or grain boundary regions. Secondly, we found that forward-bias current injection in the dark does not cause any degradation in the performance of nc-Si:H cells, in contrast to observations in a-Si:H cells. This phenomenon can be explained by assuming transport percolation through crystallites, where excess carrier recombination does not cause degradation. Third, we found that a reverse electrical bias does not reduce, but rather enhances the light-induced degradation in the nc-Si:H cell performance. This enhancement increases with the magnitude of the reverse bias. We carried out a systematic study including measurements of quantum efficiency losses and fill factors under different color filters. In view of the heterogeneity of the material structure, we proposed a “back-to-back” diode model which explains most of the experimental results. Finally, we present results of the improvement of stability of nc-Si:H cells made using hydrogen dilution profiling. We find that the nc-Si:H cells with an optimized hydrogen dilution profile show very little light-induced degradation though these cells have a high amorphous volume fraction. This indicates that the amorphous volume fraction is not the only factor determining the degradation. Other factors, such as the structure and distribution of the amorphous phase, as well as the properties of the grain boundaries, apparently play important roles in the overall stability of nc-Si:H cells.
Nucleation and Growth of Quasicrystalline Silicon Thin Films on Glass Substrate Synthesized by Ceramics Hot Wire Chemical Vapor Deposition
Authors: Middya Abdul Rafik , Liang Jian-Jun , Ghosh Kartik 
Published: April 2011

AbstractIn this work, we report on nucleation and growth of silicon thin films on glass substrate with “five-fold” symmetry and “six-fold” symmetry by ceramics hot wire chemical vapor deposition. We observed “confinement of heat and photon” is a powerful approach in developing silicon thin films with novel structure, i.e. quasicrystalline silicon thin films on glass substrate. We found unambiguously that photons emitted from the hot filament influence the nucleation of nanocrystal silicon that produces new type of silicon thin films with “five-fold” symmetry and “six-fold” symmetry.
Relationship between Phase Shift, Square-Wave Response and Density of States in Modulated Photocurrent Spectroscopy
Authors: Reynolds Steve , Main Charlie 
Published: April 2011

AbstractLow- and high-frequency modulated photoconductivity measurements (LF and HF MPC) have been made on amorphous silicon films prepared by the expanding thermal plasma (ETP) and RF PECVD techniques. Time constants have been measured by decay of square wave excitation and behavior of complex frequency response. The influence of quasi-Fermi level position has been examined. Band tail slopes of 32 meV (ETP) and 37 meV (PECVD), and defect densities of order 1018 and 1017 cm-3 eV-1 respectively are found. Tail state capture coefficients of order 3×10-8 cm3 s-1 are calculated from overlapping LF and HF regimes. Defect state values for ETP (< 10-8 cm3 s-1) are smaller than for PECVD silicon films (> 10-7 cm-3 s-1).
Low Temperature Fabrication of Microcrystalline Silicon Germanium Films by RF Reactive Magnetron Sputtering
Authors: Nakamura Isao , Ajiki Toru , Isomura Masao 
Published: April 2011

AbstractMicrocrystalline silicon germanium films (μc-SiGe) were fabricated on Corning #7059 glass substrates by the RF reactive magnetron sputtering method. The μc-SiGe films with Ge fraction of 0.7-0.8 could be crystallized at of 200 °C by H2 introduction into the sputtering gases. The absorption coefficients of the films decrease in long wavelength region corresponding to the photon energies below the energy gap by the decrease in the substrate temperature and become close to those of single crystal Si0.25Ge0.75. The dark conductivities show lower values of 10-7 S/cm at 200 °C and 300 °C with H2 introduction. Besides, the photosensitivities are observed in these samples. These results indicate that the H2 introduction into the sputtering gas has two important effects to decrease the crystallization temperature of the μc-SiGe and to improve the film properties by reducing the dangling bond defects.
Image Sensors Based on Thin-film on CMOS Technology: Additional Leakage Currents due to Vertical Integration of the a-Si:H Diodes
Authors: Miazza Clement , Wyrsch N. , Choong G. , Dunand S. , Ballif C. , Shah A. , Blanc Nicolas , Kaufmann R. , Lustenberger F. , Moraes D. , Despeisse M. , Jarron P. 
Published: April 2011

AbstractImage sensors based on thin-film on CMOS technology (TFC) have been developed. In this approach, amorphous silicon (a-Si:H) detectors are vertically integrated on top of a CMOS readout chip so as to form monolithic image sensors. In order to reduce as far as possible the dark current density (Jdark) of the TFC sensors, we have focused on analyzing and understanding the behavior of Jdark in this type of detectors. Edge effects along the periphery and at the corners of the pixel, due to the non planar configuration of the vertically integrated photodiodes, are found to be responsible for an increase of the dark current. A new and adapted solution for the minimization of Jdark is proposed, which combines the use of a metal-i-p a-Si:H diode configuration with a deposition on top of an unpassivated CMOS chip. Values of Jdark as low as 12 pA/cm2 at a reverse polarization of V = -1 V are measured on such TFC sensors.
Nano-Crystalline Silicon Thin Film Transistors on PET Substrates Using a Hydrogenation-assisted Metal-induced Crystallization Technique
Authors: Behnam Ashkan , Haji Saber , Karbassian Farshid , Mohajerzadeh Shams , Ebrahimi Aida , Abdi Yaser , Robertson Michael D 
Published: April 2011

AbstractThe effects of RF-Plasma hydrogenation and applied mechanical strain on the crystallization of silicon layers deposited on plastic substrates have been investigated where the maximum temperature remained below 170 °C for the entire process. The structural properties of the samples have been studied by optical, scanning-electron and transmission-electron microscopies where the nano-crystallinity of the silicon layers has been confirmed. The maximum average diameter of the silicon grains was 4.5 nm and occurred for an applied tensile strain of 4 %. In addition, a thin-film transistor on a plastic substrate has been fabricated and found to possess an electron mobility of 2.4 cm2/Vs.
Defect States in Excimer-Laser Crystallized Single-Grain TFTs Studied with Isothermal Charge Deep-level Transient Spectroscopy
Authors: Nadazdy Vojtech , Rana V. , Ishihara R. , Lanyi S. , Durny R. , Metselaar J.W. , Beenakker C.I.M. 
Published: April 2011

AbstractDefect states were quantitatively evaluated in single-grain (SG) Si thin-film transistors (TFTs), prepared by micro-Czochralski (grain filter) process with excimer-laser crystallization, by means of isothermal charge deep-level transient spectroscopy with a high sensitive charge/voltage converter. Its sensitivity reaches 10-16 C and it operates in the range of 2 microseconds - 10 ms. Measurements were performed on the SG-Si TFTs with various energy densities of laser crystallization, various channel areas, and positions in the grain. Our results indicate a direct correlation of fabrication parameters, parameters of the TFT determined from its transfer characteristics, and parameters of defect states (energy position in the band gap, concentration) induced by coincidence site lattice boundaries inside the location-controlled grains and by defects in the grain filter.
Characterization of Nickel Induced Crystallized Silicon by Spectroscopic Ellipsometry
Authors: Pereira Luis , Aguas Hugo , Beckers Manfred , Martins Rui M. S. , Fortunato Elvira , Martins Rodrigo 
Published: April 2011

AbstractIn this work Spectroscopic Ellipsometry (SE) was used to study metal induced crystallization (MIC) on amorphous silicon films in order to analyze the influence of different annealing conditions on their structural properties. The variation of the metal thickness has shown to be determinant on the time needed to full crystallize silicon films. Films of 100 nm thickness crystallize after 2h at 500°C using 1 nm of Ni deposited on it. When reducing the average metal thickness down to 0.05 nm the same silicon film will need almost 10 hours to be totally crystallized. Using a new approach on the modelling procedure of the SE data we show to be possible to determine the Ni remaining inside the crystallized films. The method consists in using Ni as reference on the Bruggeman Effective Medium Approximation (BEMA) layer that will simulated the optical response of the crystallized silicon. Silicon samples and metal layers with different thicknesses were analyzed and this new method has shown to be sensible to changes on the initial metal/silicon ratio. The nickel distribution inside the silicon layers was independently measured by Rutherford Backscattering Spectroscopy (RBS) to check the data obtained from the proposed approach.
Low Thermal Budget Techniques For Controlling Stress In Si1-XGeX Deposited At 210°C
Authors: Sedky Sherif , Mortagy Omar , Witvrouw Ann 
Published: April 2011

AbstractThis work reports, for the first time, on the possibility of realizing surface micromachined silicon germanium structures at 210°C, which have extremely low strain gradient (μm-1). This extremely low strain gradient is obtained by tuning the physical properties of Si1-xGex, locally, without affecting the underlying layers, by excimer laser annealing. Tuning the laser annealing condition to optimize the physical properties of PECVD Si1-xGex is challenging, especially for films deposited at low temperatures (~ 250°C or lower) due to the high hydrogen content and the poor adhesion of these films. Furthermore, optimizing some properties might be at the cost of others. To clarify this issue, it is interesting to note that reducing the electrical resistivity implies using high laser pulse fluence. This however will increase mean stress, strain gradient and surface roughness as will be shown in this work.
High Quality Hot-wire Microcrystalline Silicon for Efficient Single and Multijunction N-i-p Solar Cells
Authors: Stolk Robert L. , Li Hongbo , Franken Ronald H. , Van der Werf Karine H.M. , Rath Jatindra K. , Schropp Ruud E.I. 
Published: April 2011

AbstractIn this paper, the potential of hot-wire chemical vapor-deposited (HWCVD) microcrystalline silicon (μc-Si) for use in solar cells is explored. Incorporation of the material in the current-limiting bottom cell of two tandem cells on plain stainless steel resulted in FF values as high as 0.77, which is much higher than the highest single junction FF. A combination of experiments, calculations and computer simulations was employed to identify causes for the observed high tandem cell FF values. Both the light intensity and the spectral composition of the bottom cell illumination in a tandem were found to contribute to an increase of the bottom cell FF. The fact that the operational voltage of a tandem cell is higher than that of the current-limiting subcell, was calculated to lead to a tandem FF that can be far higher than that of the limiting cell. Com-puter simulations with the AMPS computer code show that the current mismatch in a tandem cell reduces the recombination in the current-limiting cell, possibly by slightly enhancing the internal field of that cell. Use of a 1.5 μm ìc-Si:H hot-wire deposited absorber layer in a single junction cell on a textured back reflector yielded a Voc, FF and Jsc of 0.543 V, 0.656 and 23.60 mA/cm2, respectively, which combine to an 8.4 % record efficiency for μc-Si single junction n-i-p cells with a hot-wire intrinsic layer.
Millisecond Annealing: Past, Present and Future
Authors: Timans Paul , Gelpey Jeff , McCoy Steve , Lerch Wilfried , Paul Silke 
Published: April 2011

AbstractThe challenge of achieving maximal dopant activation with minimal diffusion has re-awakened interest in millisecond-duration annealing processes, almost two decades after the initial research in this field. Millisecond annealing with pulsed flash-lamps or scanned energy beams can create very shallow and abrupt junctions with high concentrations of electrically active carriers, but solutions for volume manufacturing must also meet formidable process control requirements and economic metrics. The repeatability and uniformity of the temperature cycle is the key for viable manufacturing technology, and the lessons from the development of commercial rapid thermal processing (RTP) tools are especially relevant. Advances in the process capability require a fuller understanding of the trade-off between dopant activation, defect annealing. diffusion and deactivation phenomena. There is a strong need for a significant expansion of materials science research into the fundamental physical processes that occur at the short time scales and high temperatures provided by millisecond annealing.