Structural and Film Stress Investigation of the Interfacial Reaction in Al/SiC MicrolaminatesSpringer Science and Business Media LLC - Tập 318 - Trang 355-360 - 1993
R. B. Inturi, M. Chinmulgund, M. Shamsuzzohav, J. A. Barnard
The effect of laminate geometry and thermal treatment on the microstructural evolution of interfacial reaction products and thin film stress in Al/SiC microlaminates has been investigated by x-ray diffraction, transmission electron and optical microscopy, and thin film stress measurements. Both stress-temperature and stress-time studies are conducted. Crystalline Si of two dimensional ‘dendritic’ morphology is observed as a solid state reaction product at the Al/SiC interface following an anneal at 400 °C. This interfacial reaction is associated with a sharp change in thin film stress in laminates with very thin AI layers to a highly compressive state during isothermal annealing at 400 °C of as-deposited laminates. The change in film stress state is in agreement with the expected larger molar volume of the likely product phases.
A Highly Parallel Computer for Molecular Dynamics SimulationsSpringer Science and Business Media LLC - Tập 63 - Trang 219-224 - 2011
D. J. Auerbach, A. F. Bakker, T. C. Chen, A. A. Munshi, W. J. Paul
We are constructing a highly parallel computer array well suited to the requirements of molecular dynamics simulations of the behavior of large systems of interacting particles. A tightly coupled message passing structure is used based on a specially designed processor with 12 MFLOPS peak performance. High speed synchronous communication over a full permutation network and hardware support for operations important in molecular dynamics codes are also provided. An analysis of this configuration indicates that efficient use can be made of 1000 processors working simultaneously.
Influence of Laser Irradiation and Ambient Gas in Preparation of PZT Films by Laser AblationSpringer Science and Business Media LLC - - 1990
Akira Morimoto, Shigeru Otsubo, Tatsuo Shimizu, Toshiharu Minamikawa, Yasuto Yonezawa, Hideo Kidoh, T. Ogawa
ABSTRACTPb(Zr0.52Ti0. 48)O3 (PZT) films were prepared on r-plane sapphire substrates by the laser ablation method utilizing ArF excimer laser in O2 or N2O environment. The composition of the films deposited in O2 environment was found to be fairly close to the composition of the target material for a wide range of substrate temperatures, 400 – 750 °c. Increasing the laser fluence (the laser power density) for the ablation enhances the formation of the perovskite structure rather than the pyrochlore one. Use of N2O ambient gas instead of O2 gas enhances the formation of the perovskite structure of PZT films. Furthermore, it was found that a laser irradiation on the growing film surface during deposition enhances the formation of the perovskite structure.
Apatite Nucleation on Low Porosity Silicon in Acellular Simulated Body FluidsSpringer Science and Business Media LLC - - 1995
Leigh Canham, Christopher L. Reeves
AbstractThe response of a range of porous Si films to acellular simulated body fluids has been monitored by SEM, EDX and FTIR analyses. Quite low levels of porosity are shown here to induce hydroxyapatite growth both on top of the film, and even on neighbouring areas of bulk Si, which in isolation have no such effect. The in-vitro demonstration of hydroxyapatite nucleation by a porous semiconductor could provide further insight into the phenomenon of bioactivity and help realise a broader range of bioactive materials.
Matrix Assisted Pulsed Laser Evaporation Direct Write (MAPLE DW): A New Method to Rapidly Prototype Active and Passive Electronic Circuit ElementsSpringer Science and Business Media LLC - Tập 624 - Trang 143-154 - 2000
J. M. Fitz-Gerald, D. B. Chrisey, A. Piqu, R. C. Y. Auyeung, R. Mohdi, H. D. Young, H. D. Wu, S. Lakeou, R. Chung
We demonstrate a novel laser-based approach to perform rapid prototyping of active and passive circuit elements called MAPLE DW. This technique is similar in its implementation to laser induced forward transfer (LIFT), but different in terms of the fundamental transfer mechanism and materials used. In MAPLE DW, a focused pulsed laser beam interacts with a composite material on a laser transparent support transferring the composite material to the acceptor substrate. This process enables the formation of adherent and uniform coatings at room temperature and atmospheric pressure with minimal post-deposition modification required, i.e., ≤400°C thermal processing. The firing of the laser and the work piece (substrate) motion is computer automated and synchronized using software designs from an electromagnetic modeling program validating that this technique is fully CAD/CAM compatible. The final properties of the deposited materials depend on the deposition conditions and the materials used, but when optimized, the properties are competitive with other thick film techniques such as screen-printing. Specific electrical results for conductors are < 5X the resistivity of bulk Ag, for BaTiO3/TiO2composite capacitors the k can be tuned between 4 and 100 and losses are < 1-4%, and for polymer thick film resistors the compositions cover 4 orders of magnitude in sheet resistivity. The surface profiles and fracture cross-section micrographs of the materials and devices deposited show that they are very uniform, densely packed and have minimum resolutions of -10 jtm. A discussion of how these results were obtained, the materials used, and methods to improve them will be given
Enhanced Chemical Bonding at the Fiber-Matrix Interphase in Microwave Processed CompositesSpringer Science and Business Media LLC - Tập 189 - 1990
Lawrence T. Drzal, K. J. Hook, Raj K. Agrawal
ABSTRACTThe effect of microwave processing on the chemical interactions occurring between the carbon fiber surface and the epoxy matrix constituents was investigated using X-ray Photoelectron Spectroscopy (XPS). Monofunctional model compounds of the matrix constituents were exposed to the carbon fibers at temperatures similar to those encountered during composite processing. The microwave treatment resulted in a substantial increase in the amount of chemical interaction between the fiber surface and the epoxy resin but little difference for the amine component of the matrix when compared to thermal processing. An epoxy resin/amine hardener adduct compound used to determine the hydroxyl group interaction with the carbon fiber surface indicated a low level of chemical interaction of the hydroxyl with the carbon fiber surface under the conditions used in this study.
Temperature Dependent Transport in Microcrystalline PIN DiodesSpringer Science and Business Media LLC - Tập 609 - Trang 3231-3236 - 2000
T. Brammer, H. Stiebig, A. Lambertz, W. Reetz, H. Wagner
The optoelectronic behavior of diodes deposited by plasma enhanced chemical vapor deposition was investigated for a series of different silane concentrations in the gas phase. The purpose of this work was to correlate device characteristics with inherent properties of microcrystalline silicon by experiments and numerical simulations. Dark diode characteristics and, therefore, the open circuit voltage behavior of this series were dominated by the bulk properties of the i-layer (equilibrium carrier concentration) as shown by numerical modeling. Measurement of the solar cell output parameters as a function of the temperature showed that the fill factor of solar cells with small silane concentrations is dominated by the dark diode characteristics. This is in contrast to the temperature dependent fill factor of solar cells with large silane concentration which is limited by the extraction efficiency of the photogenerated carriers. Interface effects dominated the temperature dependent blue response. The gain in blue response increased with temperature and silane concentration by up to 200 % which revealed transport limiting material properties in the vicinity of the p/i-interface. This behavior was attributed to the nucleation region.
Mechanism of the Slow-Down of the Silicon Etch Rate by a Fluorocarbon Overlayer in CF4/H2 Reactive Ion Etching of SiliconSpringer Science and Business Media LLC - Tập 98 - 1987
Gottlieb S. Oehrlein, S. W. Robey, M. A. Jaso
ABSTRACTWe have utilized an ultrahigh vacuum surface analysis system interfaced via a load-lock to a flexible diode dry etching apparatus to study vacuum transferred CF4/H2 reactive ion etched silicon surfaces by X-ray photoemission spectroscopy (XPS). From the observation and analysis of silicon-fluorine bonding underneath the fluorocarbon film and the dependence of the abundance of fluorosilyl species on the thickness of the fluorocarbon overlayer, the role of the fluorocarbon film in the slow-down of the Si etch rate has been elucidated: The role of the fluorocarbon film is to “protect” the Si surface from attack of fluorine, rather than prevent the escape of SiF4 etch product.
Fabrication of Electrically Active Si-based Thin Films by Pulsed Laser Deposition of SiO/C Dual TargetsSpringer Science and Business Media LLC - Tập 1148 - Trang 1-6 - 2009
Yusaburo Ono, Yushi Kato, Yasuyuki Akita, Makoto Hosaka, Naoki Shiraishi, Makoto Yamaguchi, Osami Sakata, Mamoru Yoshimoto
We investigated the fabrication of Si nanocrystals, including thin films, by annealing the SiO/C/SiO thin films in an Ar atmosphere. The SiO/C/SiO trilayered thin films were deposited on α-Al2O3 (0001), Si (111), or ITO-coated borosilicate glass substrates at room temperature by pulsed laser deposition using dual sintered SiO and graphite targets. The SiO/C/SiO thin films subjected to heat treatment at 500°C included nanocrystalline Si. Measurements by synchrotron radiation X-ray diffraction indicated the formation of Si nanocrystals having a size of 5–10 nm. Fourier transform infrared spectra showed that Si–O stretching and vibrational peak intensities of the as-deposited thin film decreased remarkably after annealing. The C layer in the SiO/C/SiO trilayered thin films is considered to play a role in enhancing the chemical reaction that produces Si nanocrystals through reduction of SiO during heat treatment. The annealed SiO/C-based thin films, including Si nanocrystals, exhibited photosensitive conduction behavior in current–voltage measurements.
Nanogravimetric Evaluation of Hydrogen Uptake in Thin Film Materials by A Quartz Crystal MicrobalanceSpringer Science and Business Media LLC - Tập 1098 - Trang 1-6 - 2008
Tao Xu
To study the hydrogen storage materials in their thin film format provides a unique approach to investigate many interfacial phenomena associated with current research on hydrogen storage materials. However, the challenge is to establish a reliable method to measure weight change of at least a few tens of nanograms in pressurized hydrogen gas. We demonstrate the application of a quartz crystal microbalance for direct mass-metric evaluation of hydrogen storage materials in the pressure range of 0-40 bars. The frequency shift of a quartz crystal coated with hydrogen absorbing materials is affected by the hydrogen mass uptake on the crystal, the pressure and the viscosity of the gases, and the crystal surface roughness, of which the roughness contribution has no direct analytical expression. Through a control experiment on the same crystal in helium, the roughness contribution in hydrogen can be derived and the frequency shift due to the hydrogen mass uptake is obtained.
