bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhanced Mechanical Hardness in Compositionally Modulated Fe/Pt and Fe/Cr Epitaxial Thin Films
Authors: Daniels B. J. , Nix W. D. , Clemens B. M. 
Published: April 2011

ABSTRACTThe hardnesses and elastic moduli of sputter-deposited Fe/Pt and Fe/Cr multilayers grown on MgO(001) are evaluated as a function of composition wavelength, Λ. Structural determination by x-ray diffraction showed these films to be oriented in the plane as well as out of the plane. The mechanical behavior of these films was evaluated by nanoindentation. The combination of nanoindentation and x-ray diffraction is an attempt to determine the structural underpinnings of the mechanical behavior of these metal multilayer systems. For both systems there is no observed enhancement in the elastic modulus (the so-called supermodulus effect) across a wide range of bilayer spacings. Nanoindentation results show that for Fe/Pt multilayers, the hardness is enhanced over that expected from a simple rule of mixtures by a factor of approximately 2.5, with a maximum enhancement of 2.8 times this value at a wavelength of 25 Å. This enhancement in hardness occurs for bilayer spacings from 20 Å to 100 Å and is not a strong function of Λ over this range. Results for Fe/Cr multilayers show a hardness enhancement over a similar wavelength range of approximately two times the rule of mixtures value, with a maximum enhancement of 2.2 times this value at a wavelength of 40 Å. The larger hardness enhancement in the Fe/Pt system may be due to the structural barrier (FCC/BCC) to dislocation motion between the two materials. The dominant mechanism responsible for the hardness enhancement in Fe/Pt and Fe/Cr multilayers is not yet known, however three models for dislocation interactions which could account for the hardness enhancement in these multilayers are discussed.
Microstructure - Stress - Property Relationships in Nanometer Ge/C Multilayers
Authors: Lu Xiang , Nguyen Tai D. , Underwood James H. 
Published: April 2011

ABSTRACTA series of sputtered as-prepared and annealed Ge/C multilayer structures with periods ranging from 2 to 8 nm has been studied with high resolution transmission electron microscopy (HRTEM), x-ray scattering, and stress measurement techniques. Ge/C multilayers have potential applications as normal incidence reflective mirrors near 4.4 nm wavelength. The reflectivity and stress in these structures depend on the microstructural evolution of the component layers. The as-prepared structure of both Ge and C layers appear amorphous from TEM imaging and diffraction. Annealing at 500°C for 60 minutes leads to crystallization of the Ge layers. As the phase diagram indicates, no carbide compound has been found. X-ray scattering reveals that the multilayer period expands by as much as 10% after annealing. Both TEM images and x-ray profiles suggest that the layer structures remain well-defined upon annealing. In-situ stress-temperature measurements directly show the Ge/C multilayer microstructure evolution path. X-ray measurements show that the structures with periods near 2 nm undergo a significant improvement on optical performance with annealing. The physical mechanisms that may have caused the optical enhancement are discussed. Correlation of the stress evolution in the multilayers and in individual layers during annealing, and their relationships to the microstructures and optical properties are examined.
Polycrystalline Communication Links: Microelectronic Chip Interconnects
Authors: Sullivan Timothy D. 
Published: April 2011

ABSTRACTAll microelectronic chip interconnects are composed of polycrystalline films with properties that vary discretely with grain orientation. Techniques for dealing with this variation are developing as diminishing dimensions accentuate the effects of grain orientation. Variations in metallization microstructure affect mass transport and median failure time for metallization wearout mechanisms. Stability of adhesion layers, barrier layers and redundant conduction layers is influenced by the microstructure of the films in contact with each other. Intermetallic reactions, which are of no concern with single-level metallization, can become significant for multi level metallizations. Ti/AI systems provide typical examples of these trends.
Characterization of Textured Aluminum Lines and Modelling of Stress Voiding
Authors: Wardle S.C. , Adams B.L. , Nichols C.S. , Smith D.A. 
Published: April 2011

ABSTRACTIt is well known from studies of individual interfaces that grain boundaries exhibit a spectrum of properties because their structure is misorientation dependent. Usually this variability is neglected and properties are modeled using a mean field approach. The limitations inherent in this approach can be overcome, in principle, using a combination of experimental techniques, theory and modeling. The bamboo structure of an interconnect is a particularly simple polycrystalline structure that can now be readily characterized experimentally and modeled in the computer. The grain misorientations in a [111] textured aluminum line have been measured using the new automated technique of orientational imaging microscopy. By relating boundary angle to diffusivity the expected stress voiding failure processes can be predicted through the link between misorientation angle, grain boundary excess free energy and diffusivity. Consequently it can be shown that the high energy boundaries are the favored failure sites thermodynamically and kinetically.
Pulse-to-Pulse Laser Stability Effects on Multiple Shot Excimer Laser Crystallized a-Si Thin Films
Authors: Johnson R. I. , Anderson G. B. , Boyce J. B. , Fork D. K. , Mei P. , Ready S. E. 
Published: April 2011

ABSTRACTLaser crystallized amorphous silicon thin films on quartz exhibit a peak in the grain size, electron mobility and the Si (111) x-ray intensity as a function of the laser fluence, substrate temperature, film thickness, and the number of laser shots per unit area. The peak in grain size has also been shown to be dependent: on the stability of the pulse-to-pulse laser energy density, particularly at high shot densities. The shape of the distribution profile of the pulse-to-pulse laser fluence can significantly alter the grain growth at higher shot densities. The modified growth can be expressed by a simple model based on the mean and standard deviation of the laser energy density relative to the characteristic fluence at which the grain size, mobility, and Si (111) x-ray intensities are maximized.
Improvement of Grain Size by Crystallization of Double-Layer Amorphous Silicon Films
Authors: Moon Dae Gyu , Lee Jeong No , Im Ho Bin , Ahn Byung Tae , Nam Kee Soo , Kang Sang Won 
Published: April 2011

AbstractWe investigated the solid phase crystallization (SPC) behavior of 1000 Å amorphous Si (a- Si) films deposited by plasma enhanced chemical vapor deposition (PECVD) at various temperatures and were able to enhance the grain size of the crystallized polysilicon films using double layers of a-Si filns. The deposition temperature of monolayer a-Si films varied from 200 to 400 °C and the films were recrystallized at 600 °C in nitrogen. As the deposition temperature increased, the incubation time was decreased and both the nucleation rate and growth rate were increased. Especially, the nucleation rate strongly depended on the deposition temperature.Since the Si-SiO2 interface provides a large number of nucleation sites, it is desirable to suppress nucleation at the interface. As an idea we employed a structure with double layer a-Si films. The bottom a-Si layer deposited at lower temperature could suppress the nucleation at the Si-SiO2 interface while the top a-Si layer deposited at higher temperature could nucleate with a smaller number of nucleation sites. The incubation time and transformation behavior were determined by the deposition temperature of the top layer. As an example, the grain size of the double layer film deposited sequentially at 150 °C and 200 °C enhanced to 1.8 μm while that of the monolayer film deposited at 200 °C was 1.4 μm.
High Deposition Rate Pecvd Processes For Next Generation Tft-Lcds
Authors: Westendorp J. F. M. , Meiling H. , Pollock J. D. , Berrian D. W. , Laflamme A. H. , Hautala J. , Vanderpot J. 
Published: April 2011

AbstractThe demand for lower cost per panel in TFT-LCD production is driving the PECVD market to deposition systems that combine high throughput and uptime with high yield. Today it is generally believed that a multichamber system that combines a number of single-panel deposition chambers is the best way to achieve these goals.For these PECVD systems to be economical, the deposition rate of a-Si:H, SiNx and SiO2 has to be in the 1200–1500 Å/min range. In 13.56 MHz parallel-plate glow discharge systems SiNx and SiO2 deposition rates exceeding 1500 Å/min are commonly achieved, whereas the deposition rate of a-Si:H is limited to 100–200 Å/min due to powder formation. Over the last 5 years significant progress has been made to increase the deposition rate of a-Si:H. Methods include the use of very-high-frequency glow discharge (VHF-GD) and pulsing of the rf discharge. However, substrate sizes never exceeded 100mm×100mm.We have developed a multichamber PECVD system for TFT-LCD production where VHFGD is used to obtain uniform high deposition rates for (doped) semiconductors and insulators, such as a-Si:H, n+ a-Si:H, SiNx and SiO2 over areas as large as 470mm×370mm. Even at deposition rates well above 1200 Å/min hydrogen in a-Si:H is exclusively bound as monohydride. The optoelectronic properties of the films are at least as good as those of their 13.56 MHz counterparts and thus good-quality TFTs can be obtained. At the same time the number of added particles is low allowing for high production yields.
New Materials For Laser Repair Of Active Matrix Liqiuid crystal Displays
Authors: Comita Paul B. , Larson Carl E. 
Published: April 2011

AbstractNew materials have been developed for the repair of electrical open defects in AMLICD panel circuitry The metal-containing precursors are volatile, easily pyrolyzed to high purity conducting metal, and are decomposed at temperatures which will not damage the glass substrate or thin film circuitry. New materials have been developed for additive metal repair as well as additive passivation repair. The repair or data line metallurgy on prototype arrays has been achieved, resulting in electrical resistances of the repaired interconnects which were comparable to those of unrepaired interconnects of identical geometry.
Alignment Of Smectic Liquid Crystal Molecules By Grated Glass And Silicon Substrates
Authors: Martínez-Miranda L. J. , Smela E. , Liu H. 
Published: April 2011

AbstractWe present the results of a study of the effect of photolithographed gratings on glass and silicon wafers on the alignment of smectic liquid crystal molecules. The gratings have periods in the range of 200nm − 200µm, and depths of up to 2µm. We found that smectic liquid crystals alignsharplyalong the gratings, depending on the temperature cycling method used in loading the sample. This result applies both to silicon gratings as well as glass gratings, despite the increased roughness observed in glass gratings. The quality of the alignment is uniform in the range 664nm − 24µm, and breaks down outside this region, setting lower and upper boundaries for grating preparation.
Transparent Conducting Films Of GaInO3 By Sputtering
Authors: Kwo J. , Carter S. A. , Cava R. J. , Hou S. Y. , Phillips J. M. , Rapkine D. H. , Thomas G. A. , Dover R. B. Van 
Published: April 2011

AbstractOne of the critical components used in the display device is the transparent conducting electrode. A new candidate for the transparent conductor, GaInO3 containing a tetrahedrally coordinated Ga site was identified recently, and shows good promise of improved optical transmission in the blue wavelength over ITO due to a high band gap ˜3.3 eV. Thin films of GaInO3 with cation dopants Ge for Ga, and Sn for In, respectively, have been prepared using dc reactive magnetron sputtering. Among the growth parameters, oxygen partial pressure plays the decisive role in affecting the film quality. A post-anneal in H2-rich atmosphere at 300C effectively reduced the oxygen content and lowered the resistivity to ∼3.0 mΩ-cm; however, the final resistivity appears to be insensitive to cation dopant concentrations. Concurrently, Hall measurements indicated a carrier concentration in the mid 1019 range for all films. Our structural analysis by x-ray and SEM has suggested that a limited Sn solubility in the film to less than 5 %. Doping appears to be due both to oxygen vacancies and aliovalent ion substitutions. The optical transmission of this new material is indeed superior to ITO over the entire visible spectrum, especially in the green and blue wavelengths. More work is underway to identify appropriate dopants for attaining better film conductivity.
Mechanisms Of Liquid Crystal Alignment On Buffed Polyimide Surfaces
Authors: Kikuchi Hirotsugu , Logan J. A. , Yoon Do Y. 
Published: April 2011

AbstractThe surfaces of poly(amic acid) and cured polyimide films, subjected to different buffing and cure profiles, have been examined by atomic force microscopy (AFM). The ability of these buffed polymer surfaces to align nematic and chiral smectic C liquid crystals were also investigated. These studies show that the presence of microgrooves on buffed polymer surfaces are not necessary for alignment of liquid crystals. Rather, it is concluded that the liquid crystal alignment is mainly caused by the anisotropic intermolecular interactions between liquid crystal molecules and the polymer chains oriented by buffing. For the alignment of smectics, both the degree of order and mechanical properties of polyimide films are found to be important factors.
In-Situ Crystallization and Doping of a-Si Film by Means of Spin-On-Glass
Authors: Sakoda Tomoyuki , Kim Chang-Dong , Matsumura Masakiyo 
Published: April 2011

AbstractA novel technique has been proposed for selective and in -situ excimer-laser crystallization and doping to thin poly-Si films. Dopant atoms are supplied, during the Si laser crystallization process, to the Si film on glass from the doped SOG (spin-on-glass) film coated on the top. Conductivity of the processed film was increased to more than 10S/cm from about 10−8S/cm of the starting film. This technique has been applied to the bottom gate amorphous-Si TFTs with self-aligned poly-Si source and drain. The electron field-effect mobility was 1.0cm2/Vs and the on/off current ratio was more than 106. No parasitic effects were observed, and the hole conduction was effectively. This in-situ crystallization and doping technique can also be applied to the top gate a-Si TFT process.
High Mobility Non-Hydrogenated Low Temperature Polysilicon TFTs
Authors: Plais F. , Legagneux P. , Kretz T. , Stroh R. , Huet O. , Pribat D. 
Published: April 2011

AbstractWe have fabricated polysilicon (poly-Si) thin film transistors (TFTs) using a standard 4-mask sequence, with self-aligned ion implantation for source and drain doping. The active layer was obtained by solid phase crystallisation of high purity Si2H6-deposited amorphous Si, whereas the gate oxide was synthesised by a novel plasma deposition technique, namely distributed electron cyclotron resonance plasma enhanced chemical vapour deposition (DECR PECVD). We have obtained high carrier mobilities (70 cm2V−1s−1 for electrons and 40 cm2V−1s−1 for holes) with an excellent uniformity and without the need for a post-hydrogenation treatment. Moreover, we show that the TFT characteristics are practically insensitive to hot carrier effects.
The Quasioptical Gyrotron, A High-Power, Tunable Source of Millimeter-Wave Radiation
Authors: Fliflet Arne W. , Fischer Richard P. 
Published: April 2011

ABSTRACTThis talk will summarize the present state of the art of the quasioptical gyrotron (QOG), an alternative gyrotron configuration which has been under development primarily in the U.S. and Switzerland for heating fusion plasmas in tokamaks and other high-power millimeter-wave applications. The QOG features an open-mirror Fabry-Perot resonator instead of the conventional waveguide cavity used in conventional gyrotrons. This gives the QOG the potential for wide tunability, advantages for high-power operation, and facilitates the use of a depressed collector for spent electron beam energy recovery. An experimental QOG has been tuned from 85 to 130 GHz by varying the applied magnetic field. QOGs have produced peak powers up to 600 kW for 13 μs pulses and 100 kW for 10 ms pulses. Electronic efficiencies up to 22% have been achieved at 85 GHz, and operation with a depressed collector yielded an overall efficiency of 30%. The design of a multi-kW CW QOG tunable from 80 to 120 GHz is discussed.
Numerical Modeling and Simulation of Electromagnetic Drying Processes
Authors: White Mikel J. , Gartside Paul J. , Iskander Magdy F. 
Published: April 2011

ABSTRACTElectromagnetic drying processes have been used in industrial applications for many years. New materials with different properties and structures have been recently developed which required the development of new drying systems capable of effectively drying the new materials. In this paper, we use Finite-Difference Time-Domain (FDTD) to model and simulate realistic electromagnetic drying processes including induction heating and RF drying. The power deposition patterns obtained from the FDTD code is also used in a finite-difference heat transfer code to evaluate the temperature distribution pattern and optimize rates of drying. Sample parameters used to analyze the RF drying and the induction heating processes include the sample conductivity, dielectric constant along with size, orientation and the geometric arrangement. Specifically, we analyzed the operating frequency, coil pitch, sample to coil diameter ratio, and the possible placement of multiple samples in an induction heating process. Effects investigated in a parallel plate RF drying system include: electrode spacing, electrode length and width, and the spacing between multiple samples. Results of electromagnetic power distributions and temperature patterns are presented.
Microwave Tower Absorption Profile in a Cylindrical Sample Contained in a Resonant Cylindrical Cavity
Authors: Jackson H. W. , Barmatz M. , Wagner P. 
Published: April 2011

ABSTRACTAn analytic approach is used for evaluation of the microwave power absorption profiles in a lossy dielectric cylinder coaxially aligned in a cylindrical cavity. This approach, based on a cylindrical shell model, also determines the normal mode frequencies and fields. Absorption profiles inside the sample will be presented for resonant modes that are intrinsically angular independent. In addition, results will be presented for special modes that are not intrinsically angular independent, but produce angular independent absorption for time average values. This new development broadens the class of modes that can be used in heating materials when isotropy about an axis is needed. We demonstrate how this model can extend the application of cavity perturbation theory for determining dielectric constants to cylinders of larger diameter. Implications of these results for microwave processing of materials are also discussed.
Modeling the Thermomechanical Response of Ore Materials During Microwave Processing
Authors: Williamson R. L. , Salsman J. B. , Tolley W. K. 
Published: April 2011

ABSTRACTA finite element numerical model is used to predict the thermal and mechanical response of mineral-bearing ores irradiated by microwave energy. The model considers a small, spherical, pyrite particle surrounded by a matrix of calcite. Power density data are determined from the dielectric properties of the mineral and host rock materials at typical microwave frequencies and power capabilities. The effects of varying power density and mineral particle diameter are studied. Using power densities within the expected achievable range for pyrite, significant temperature differences are predicted between the mineral particle and host rock. These temperature gradients lead to circumferential tensile stresses in the host rock well in excess of the reported uniaxial tensile strength of common rock materials. It is shown that, for a fixed microwave energy source, both the temperature difference between the mineral and host rock, and the peak tensile stress in the host rock are reduced as the mineral particle size is reduced. Recent experimental efforts to corroborate this numerical study are briefly described.
Nox Reduction on Char using Microwaves Carolynn
Authors: Buenger W. , Peterson Edward R. , Cha Chang-Yul 
Published: April 2011

ABSTRACTMore than 18 million tons of nitrogen oxide (NO and NO2) are emitted into the air over the United States each year. These oxides contribute to the formation of acid rain and street level ozone, and are most concentrated in areas of industrial and commercial activity. The response of the Environmental Protection Agency to the problem has been to legislate anti-pollution laws and regulations which will be enforced in increasingly strict stages beginning in 1997. Existing NOx abatement technologies do not meet the long range NOx abatement needs of the processing industries and utilities.Char, a heat treated and volatile form of coal, can effectively adsorb NOx from waste gas. Microwave energy, when properly applied, can convert the NOx and carbon via reduction to nitrogen and carbon dioxide. The basic principles of this technology are taught as well as some of the pertinent development aspects currently under investigation.
The use of Magnetite as a Facilitator for the Microwave Heating of Contaminated Soils
Authors: George Clifford E. , Rao Gunda V.N. , Guice Jennifer D. 
Published: April 2011

ABSTRACTPrevious research work in the area of microwave heating for low temperature thermal desorption of contaminates has led to a novel method of delivering heat energy to contaminated materials (soils) that have poor electrical characteristics for the absorption of microwaves. This method involves the use of a heating facilitator. The facilitator, which in this case is a ferromagnetic material (magnetite), is admixed with the soil or sludge to be treated. When exposed to microwave energy, the facilitator preferentially absorbs the energy and transfers heat to the contaminated matrix. Using this method, it has been possible to achieve temperatures in excess of 900 °C (1650 °F) in test soils. At these temperatures, even the highest molecular weight hydrocarbon contaminants are compelled to desorb from the soil.The advantage of using magnetite is that it can be separated by conventional separation methods for recycle and reuse. The technology has implications of being useful in several chemical processing operations.
Microwave Processing at the University of Florida
Authors: Clark D. E. , Folz D. C. , Schulz R. L. , Fathi Z. , Cozzi A. D. , Boonyapiwat A. , Komarenko P. , DiFiore R. , Jones C. B. 
Published: April 2011

ABSTRACTMicrowave energy for processing materials is emerging as a vital manufacturing technology for the nineties and beyond. Research to date has shown significant advantages in several areas, including drying and sintering, joining, surface modification and waste remediation. Increased processing rates, improved physical and mechanical properties and, in some cases, reduced hazardous emissions have sparked the interest of many manufacturers in the ability to integrate microwave processing techniques into existing and future manufacturing operations. This presentation will provide an overview of the microwave processing research and development work in progress at the University of Florida.