bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron Holography of Flux Lattices in Niobium
Authors: Bonevich J.E. , Harada K. , Matsuda T. , Kasai H. , Yoshida T. , Pozzi G. , Tonomura A. 
Published: April 2011

ABSTRACTMagnetic lines of force penetrating a superconducting thin foil have been investigated by means of electron holography. A field-emission TEM with a specially constructed cold stage was used to cool a Nb thin foil down to 4.5 K and apply magnetic fields up to 100 G. The specimen is tilted by 45° to both the electron beam and the magnetic field (applied horizontally) allowing the 2-D lattice of penetrating flux-lines to be discerned. The phase distribution of electrons transmitted through the specimen were quantitatively measured. Interference micrographs revealed tiny regions where the phase distribution rapidly changed. These regions coincided spatially with the spot-like contrast observed by Lorentz microscopy and were found to be quantized vortices containing a flux of h/2e. The experimental results were in good agreement with those predicted by theoretical simulations. Experiments exploring the vortex inner core structure at high resolution are presented.
Spatially Resolved Local Atomic Structure from Exelfs
Authors: Stern E. A. , Qian M. , Sarikaya M. 
Published: April 2011

ABSTRACTEXELFS, extended energy loss fine structure, is one of the spectroscopic techniques provided by electron energy loss spectrometer in the transmission electron microscope. Here, EXELFS is described for its potential use for determining nanoscale physical properties of complex materials. It is demonstrated that EXELFS analysis, like EXAFS, extended X-ray absorption fine structure in bulk materials, provides short-range structural information such as atomic nearest-neighbors and their distances in amorphous an crystalline samples. Some of the problems that hindered the development and wide use of EXELFS were discussed and their solutions are presented. Further solutions and future prospects are discussed.
Tem Study of the Pt-Ru BI-Metallic Catalyst Formation
Authors: Ma Chaoying , Kowalak A. D. , Sung Changmo 
Published: April 2011

ABSTRACTPt colloidal particles with large surface areas are effective electrocatalysts which can be applied in methanol fuel cells. The efficiency of the Pt catalyst can be greatly increased if it is incorporated with a second component such as Ru. By applying TEM, EDXS and XRD, the chemical composition, particle size and crystallinity of Pt and Pt/Ru colloidal particles during synthesis procedure are investigated in this research.
Raman Spectroscopy of Size Selected, Matrix Isolated Si Clusters
Authors: Ogura A. , Honea E. C. , Murray C. A. , Raghavachari K. , Sprenger W. O. , Jarrold M. F. , Brown W. L. 
Published: April 2011

ABSTRACTWe report results of Raman spectroscopy of size selected, matrix isolated Si clusters. Cluster ions produced by laser vaporization are size selected by a quadruple mass spectrometer and co-deposited with cryogenic matrices onto a substrate at ∼15K. A surface-plasmon-polariton-enhanced Raman geometry is used to gain adequate signal.The observed vibrational frequencies from Si4, Si6 and Si7 are compared with theoretically calculated Raman active modes based on the structures of planar rhombus, distorted octahedron and pentagonal bipyramid, respectively. The agreement is excellent. Cluster agglomeration is observed when cluster concentrations exceed ∼0.3% by volume in the matrix and/or with annealing at ∼28K, below the temperature of matrix evaporation.
Annular Dark Field Imaging in Stem
Authors: Hillyard Sean , Silcox John 
Published: April 2011

ABSTRACTAnnular dark field scanning transmission electron microscopy (ADF STEM) is chemically sensitive at high spatial resolution (e.g., 1.8ë at 100keV). Images can be digitally acquired and recorded, permitting quantitative analysis. It is particularly powerful when used in combination with complementary analysis modes such as x-ray microanalysis and transmission electron energy loss spectroscopy. Critical to the interpretation of these data is an understanding and determination of the electron probe intensity, shape and propagation characteristics inside the specimen. Quantitative measurements of diffraction patterns and images in comparison with computer-based simulations (including phonon scattering) provide a basis for developing that information. Results of a series of studies are reviewed that address questions such as defocus and other instrumental factors, and also the formation of channeling peaks that appear on the atomic columns along zone axes. For example, along Si(100) a peak forms and penetrates over 500ë whereas along Ge(100) it developes rapidly but disappears in less than 200ë. In higher atomic number elements, the penetration is even less (e.g. 1 O0ë for In).
Investigation of the Vicinal Ge(001) Surface with Stm
Authors: Kersten Bart A.G. , Sjerps-Koomen Lianda , Zandvliet Harold J.W. , Blank Dave H.A. 
Published: April 2011

ABSTRACTThe morphology of Ge(001) has been investigated with a UHV - Scanning Tunneling Microscope. The Ge(001) surface was misoriented towards the [011] direction with a miscut angle varying from 0.4° to 5°. The surface stress was found to have considerable influence on the step edge configuration as well as the position of the steps with respect to each other.
Reliability Implications of Defects in High Temperature Annealed Si/SiO2/Si Structures
Authors: Warren W. L. , Fleetwood D. M. , Shaneyfelt M. R. , Winokur P. S. , Devine R. A. B. , Mathiot D. , Wilson I. H. , Xu J. B. 
Published: April 2011

ABSTRACTHigh-temperature post-oxidation annealing of poly-Si/SiO2/Si structures such as metal-oxidesemiconductor capacitors and metal-oxide-semiconductor field effect transistors is known to result in enhanced radiation sensitivity, increased 1/f noise, and low field breakdown. We have studied the origins of these effects from a spectroscopic standpoint using electron paramagnetic resonance (EPR) and atomic force microscopy. One result of high temperature annealing is the generation of three types of paramagnetic defect centers, two of which are associated with the oxide close to the Si/SiO2 interface (oxygen-vacancy centers) and the third with the bulk Si substrate (oxygen-related donors). In all three cases the origin of the defects may be attributed to out-diffusion of O from the SiO2 network into the Si substrate with associated reduction of the oxide. We present a straightforward model for the interfacial region which assumes the driving force for O out-diffusion is the chemical potential difference of the O in the two phases (SiO2 and the Si substrate). Experimental evidence is provided to show that enhanced hole trapping and interface-trap and border-trap generation in irradiated high-temperature annealed Si/SiO2/Si systems are all related either directly, or indirectly, to the presence of oxygen vacancies.
Precipitate Drifting and Coarsening Caused by Interface Electromigration
Authors: Ma Qing , Suo Z. 
Published: April 2011

ABSTRACTA mechanism is proposed to explain electromigration-enhanced precipitate coarsening in Al-Cu alloy interconnects. The interface between the α-phase matrix and a θ-phase Al2Cu precipitate is incoherent, along which both Al and Cu atoms diffuse under an applied electric field. Depending on the relative mobility of Al and Cu, the diffusion causes the precipitate to migrate towards either the positive or the negative electrode. The velocity of a spherical precipitate is proportional to the electric field and the mobilities and inversely proportional to its radius. A critical electric field or precipitate radius exists, above which the precipitate can penetrate a grain boundary. Consequently, the precipitates agglomerate by the synergism between the surface tension-induced ripening and the current-induced migration. The resulting particles are distantly separated, depleting Cu atoms from the rest of the interconnect. The mechanism appears to limit the lifetime of interconnects having bamboo-like grains, tested below 300°C, less than half of the melting temperature of Al.
CeO2/YSZ and SrTiO3/YSZ Double Buffer Layers Deposited on Si(100) by Laser Ablation
Authors: Sanchez F. , Aguiar R. , Ferrater C. , Peiro D. , Queralt X. , Varela M. 
Published: April 2011

AbstractYttria stabilized zirconia (YSZ), SrTiO3 and CeO2 thin films have been widely used as buffer layers in YBa2Cu3O7-x (YBCO) deposition on silicon substrates. YBCO superconducting properties are limited by lattice mismatches between YSZ and YBCO, and chemical interaction of CeO2 and SrTiO3 with silicon. In order to avoid these problems we have deposited CeO2/YSZ/Si(100) and SrTiO3/YSZ/Si(100) bilayers by laser ablation. Wide temperature and pressure ranges have been studied. The influence of the intermediate layer on the CeO2 and SrTiO3 films properties has been studied. Previous studies were performed on films of each material on Si(100) and YSZ(100) single crystals. The surface of the films and bilayers is smooth without microcracks and only few droplets are found. Only small interdiffusion is observed in all the cases. Texture of the films changes with deposition conditions. Epitaxial growth of CeO2 has been found both on YSZ(100) single crystals and YSZ buffers on Si(100).
Candidate HTSC Film Substrates of Complex Oxide Perovsk1te Compositions
Authors: Guo Ruyan , Bhalla A. S. , Roy Rustum , Cross L. E. 
Published: April 2011

AbstractThe research focused upon generating new substrate materials for the deposition of superconducting yttrium barium cuprate (YBCO) has yielded several new hosts in complex perovskites, modified perovskites, and other structure families. New substrate candidates such as Sr(Al1/2Ta1/2)O3 and Sr(Al1/2Nb1/2)O3, Ba(Mg1/3Ta2/3)O3 in complex oxide perovskite structure family and their solid solutions with ternary perovskite LaAlO3 and NdGaO3 are reported. Conventional ceramic processing techniques were used to fabricate dense ceramic samples. A laser heated molten zone growth system was utilized for the test-growth of these candidate materials in single crystal fiber form to determine crystallographic structure, melting point, thermal, and dielectric properties as well as to make positive identification of twin free systems. Some of those candidate materials present an excellent combination of properties suitable for microwave HTSC substrate applications.
Anisotropy in Epitaxial Fe3O4 and NiFe2O4 Thin Films
Authors: Margulies D. T. , Parker F. T. , Spada F. E. , Berkowitz A. E. 
Published: April 2011

AbstractFe3O4 and NiFe2O4 films were deposited on <100> and <110> MgO substrates by dc magnetron reactive sputtering. X-ray diffraction studies indicate epitaxial films under an inplane tensile stress. Magnetization studies show that the moments of the films are unsaturated in 70 kOe applied fields and they approach bulk values only in extrapolation. Conversion electron Mössbauer spectroscopy (CEMS) studies indicate bulk parameters for the Fe3O4 films, but show deviations from bulk properties for NiFe2O4 films. CEMS studies further indicate a random moment distribution for all films which is an unexpected property. In-plane torque curves are discussed in terms of single crystal behavior. The effect of the inplane tensile stress is also indicated in the torque curves.
Heating Rate Effects in Rapid Thermal Annealing of Arsenic Implanted Silicon
Authors: Souza J.P. de , Fichtner P.F.P. , Sadana D.K. 
Published: April 2011

ABSTRACTCross section TEM and channeling analysis show that the heating rate (HR) of a rapid thermal annealing (RTA) cycle affects the residual defect distribution in Si implanted with As+ to a heavy dose (≈ 1016 cm−2). Two defect bands are observed after solid phase epitaxial growth (SPEG): the first one centered at a depth corresponding to the projected range of the As (band I), and the second one located at depth corresponding to the original amorphous crystalline (a-c) interface (band II). The density of defects in band I is found to increase with the As dose, and with the annealing temperature (550 - 650°C, furnace annealing). However, for RTA (800 - 1000°C) both the density and depth distribution of these defects are dependent on HR. We propose that Si self-interstitials (SiI) are created at the a-c interface when As becomes substitutional during SPEG. The SPEG velocity determines whether the SiI are accommodated in the amorphous Si layer (low velocities) or are captured by the regrowing c-Si (high velocities)
Thermal-Radiation Absorption Characteristics of Patterned Wafers During Rapid Thermal Processing
Authors: Wong Peter Y. , Miaoulis Ioannis N. 
Published: April 2011

ABSTRACTMicroscale radiation effects are responsible for the dependence of absorption and temperature distributions on the geometry of the layering structures and the spectral characteristics of the heat source. The effect of patterned wafers, which may contain several different structures and materials, on the wafer absorption characteristics are investigated for rapid thermal processing. A numerical model to determine the thermal radiative absorptivity of the wafer for different structures and materials is presented for different heating conditions. The resulting transient effects are determined numerically for different rapid thermal processes. The changes in radiative properties for rapid thermal annealing and chemical vapor deposition are investigated for patterned wafers.
Monte Carlo Simulation of Radiative Heat Transfer in Rapid Thermal Processing (RTP) Systems
Authors: Cole J. Vernon , Knutson Karson L. , Jensen Klavs F. 
Published: April 2011

ABSTRACTWe present a general purpose Monte Carlo method for the simulation of radiation heat transfer in rapid thermal processing (RTP) chambers. Three-dimensional mesh generation software is used to discretize the surfaces within the system, allowing the simulation of realistic chamber and reflector designs. An adaptive subdivision of the chamber geometry reduces the number of raysurface intersections which must be computed. The method models internal reflection, absorption, and transmission within participating media, and includes wavelength, temperature, and material dependent optical properties. Radiation heat transfer simulations are used to examine a reflector assembly, and to test the assumptions of optical wafer temperature measurement techniques.
Importance of the Photoeffects in Rapid Isothermal Processing (RIP)
Authors: Singh R. , Mavoori J. , Thakur R. P. S. , Narayanan S. 
Published: April 2011

ABSTRACTThere are fundamental differences between conventional furnace processing (CFP) and rapid isothermal processing (RIP). The radiation spectrum of a conventional furnace consists of photons in the infrared and longer wavelength regions, whereas the spectrum of the incoherent light sources used in RIP consist of some ultraviolet, visible, and infrared photons. As compared to CFP, the photophysical and photochemical effects associated with RIP provide the capability of lower temperature processing. Due to photoeffects in RIP, differences are observed in junction movement and defect evolution with different lamp configurations and different kinds of lamps having differing spectra. This implies that diffusion models, in addition to considering processing time and temperature, should also account for the lamp configurations and spectra of the heating sources. The fundamental understanding of photoeffects in RIP can be further exploited to reduce the overall thermal budget used in the manufacturing of semiconductor devices. In this paper we present our study of photoeffects in RIP, which can be of help in the design of the next generation of RIP equipment.
Silicide Formation by Rapid Thermal Processing
Authors: Chen L.J. , Lur W. , Chen J.F. , Lee T.L. , Liang J.M. 
Published: April 2011

ABSTRACTAn overview of silicide formation by rapid thermal processing is presented. Recent progresses on device applications, phase formation, growth kinetics, thermal stability, epitaxial growth, formation of metastable phase, vacancy ordering in rare-earth silicides and Ti-based shallow junctions involving rapid thermal processing are used as examples to highlight the applications of rapid thermal processing in connection with silicide formation.
Hydrodesulphurization of Thiophene by Transition Metal Sulphides: The Electronic Basis for Catalytic Activity
Authors: Smit Timo S. , Johnson K. H. 
Published: April 2011

AbstractTransition metal sulphides (TMS) have the ability to catalyze the hydrodesulphurization (IDS) of thiophenes occurring in oil. The catalytic activity varies strongly across the TM series, and can in some cases be significantly enhanced by the addition of promotor elements (e.g. Co/Ni in MoS2).From a series of density functional (DF) scattered-wave electronic structure calculations on first, second and third row TMS, electronic parameters related to the catalytic activity have been identified. The occupation and topology of metal-sulphur antibonding orbitals near the Fermi level are particularly important. An activity parameter, I, which is a measure of the strength of the interaction between metal d and sulphur 3p electrons, correlates well with the experimental HDS activities.
A New Route to Generation of co With a Redox System of Mixture of Metal Oxide and Carbon
Authors: Mimori K. , Hasegawa N. , Tsuji M. , Tamaura Y. 
Published: April 2011

AbstractAn endothermic chemical system composed of pulverized iron-based oxide and carbon powder has been investigated by using the temperature swing method (TSM) at 700 to 800 °C. Ferrite of Mn and Zn, and magnetite were studied. The last material showed the most promising result. In the TSM, magnetite as the working material was reduced to wustite and carbon was concurrently oxidized to CO in a flow of N2 gas at 800 °C (the activation step of the metal oxide). In the reverse process, in a flow of CO2, the wustite was oxidized to magnetite and injected CO2 was reduced to CO at 700 °C (the reduction step of CO2 to CO). Following the reduction step, the chemical composition of the magnetite phase was restored to that existing prior to the activation step. The total amount of oxygen donated to carbon during the activation step was the same as that taken from the magnetite during the reduction step. In this system, the following net reaction can be realized at temperatures of 700 to 800 °C: C + CO2 → 2CO. The process will therefore serve for the utilization of coal and other carbonaceous compounds in much lower temperatures than are employed in the traditional water gas and producer gas reactions.
Highly CO2-Soluble Chelating Agents for Supercritical Extraction and Recovery of Heavy Metals
Authors: Yazdi A. , Beckman E. J. 
Published: April 2011

AbstractCarbon dioxide is an attractive organic solvent in today's chemical process environment in that it is non-flammable, inexpensive, and exhibits low toxicity. Further, materials solubilized in carbon dioxide are easily and completely recovered/concentrated from solution via a simple pressure quench. Despite these favorable properties, CO2 is non-polar, and as such is a very poor solvent for materials such as conventional metal chelating agents, thus blocking application of carbon dioxide in metal extraction/recovery. Consequently, we are exploring the molecular design of materials which are highly CO2-philic, that is, they exhibit solubilities in carbon dioxide which are significantly greater than alkanes with the same number of main-chain atoms. By functionalizing chelating moieties with CO2-philic oligomers, we have generated materials which both effectively extract metals from solid matrices and which dissolve in carbon dioxide in significant quantities.
A Synergistic Approach to Environmental Concerns in Large Scale MOCVD Processes
Authors: Thompson A. G. , Tompa G. S. , Zawadzki P. A. , Mckee M. , Beckham C. , Powers A. , Gurary A. , Moy K. , Schumaker N. E. 
Published: April 2011

AbstractProcesses used in the production of epitaxial III-V semiconducting materials employ a wide variety of materials that are environmentally hazardous. As production volumes increase, the need to manage these materials becomes a serious concern. As the leading supplier of production scale single and multi-wafer MOCVD systems, we have taken the approach of minimizing the generation of waste by designing our reactor for high reactant utilization efficiency, and then trapping the remainder so that the exhaust stream is clean. We have paid particular attention to both operational efficiency and operator safety. The traps may be simply removed and replaced, with cleaning being performed off line. The trapped materials are reduced to an inert state for subsequent commercial disposal; this is particularly important for phosphorus, which can be highly flammable if improperly handled. The reactor chamber deposits occur below the wafer level and typically are cleaned only after several hundred deposition cycles. These factors contribute to a quick cycle time and high uptime, both of which increase throughput. These issues become more important as the reactor size is increased and when multiple shifts are utilized. These points are exemplified by our operational experience with our new Enterprise series, which holds four 100mm wafers (or seventeen 50mm wafers) per run. We will discuss the progressive trapping of solid As and P compounds and those hydride gases which are not completely decomposed in the reaction chamber. The use of computer modeling to scale the process to larger dimensions and to optimize the deposition conditions will also be discussed.
Reprocessing of Sintered and Melt High Temperature Superconducting Materials
Authors: Vipulanandan C. , Martinz B. 
Published: April 2011

AbstractIncreasing use of High Temperature Superconducting Ceramics (HTSC) in various applications and the cost of the new superconducting powder dictated the need for evaluating the potential of reusing the old HTSC material (yittrium-barium-copper oxide (YBCO); YBa2Cu3O7-x) with minimum reprocessing. This study examined various methods to reprocess two years old sintered and melt bulk YBCO ceramics. YBCO components were ground and processed with and without adding various amount of silver powder, organic binders and new YBCO powder. The reprocessed YBCO powder was also characterized at every step of processing using X-ray diffraction (XRD) and Differential Thermal Analysis (DTA) to identify impurities.The old YBCO components were first crushed and then ground using automatic grinder and a jet-mill. The ground powder was then mixed with additives and/or binders and compacted uniaxially to 45 ksi. The range of sintereing temperatures from 905 °C to 980 °C were selected based on the past history of sintering/melting temperatures. The reground powder was found to have impurity phases due to its exposure to carbon dioxide and humidity in the atmosphere. Addition of Ag powder resulted in higher relative densities at lower sintering temperatures. The need for re-calcination of used powders was also considered to improve the performance of reprocessed powders. The sintering temperature was selected based on achieving 85% relative density. The results show that the reprocessed powders have to be sintered at higher temperatures than their previous history. The sintered and melt-textured YBCO made from reprocessed powder had similar or better superconducting properties compared to the new powder.
Effects of the Physical Structure of Alumina/Copper Oxide Solids On Their Reactivity for SO2 Removal From Flue Gases
Authors: Dall'aglio Laurent A. , Sotirchos Stratis V. 
Published: April 2011

AbstractCuO/Al2O3 sorbents based on three aluminas of different pore structure and surface area around 125 m2/g were prepared. Two of the aluminas exhibited bimodal pore size distribution, while the third had narrow unimodal distribution. The effect of copper loading on the physical characteristics of the aluminas (pore size distribution and surface area) was examined using mercury porosimetry and gas adsorption. The reactivity of the sorbents towards SO2 was investigated by carrying out thermogravimetric experiments using simulated flue gas.