bluuebunny/crossref_metadata_2025_split huggingface dataset:
Closed-Loop Thickness Control of Resonant-Tunneling Diode Mbe Growth Using Spectroscopic Ellipsometry
Authors: Celii F. G. , Kao Y.-C. , Moise T. S. , Woolsey M. , Harton T. B. , Haberman K. 
Published: April 2011

AbstractThe room temperature electrical characteristics of AlAs/InGaAs/InAs resonant-tunneling diode (RTD) devices are sensitive to sub-monolayer thickness changes, and present a challenging case for closed-loop control. We prepared stacked RTD structures by MBE in which the strained AlAs barrier thicknesses were controlled based on an in situ spectroscopic ellipsometry (SE) system. The short-term and long-term reproducibility of RTDs grown under SE-based control was compared with similar samples grown by “dead-reckoning” (timing-based shutter openings coupled with pre-growth flux calibrations). SE-based calibration can compensate for long-term flux drift, but closed-loop thickness control did not provide a significant improvement over deadreckoning in terms of short-term RTD reproducibility.
Spectroscopic Ellipsometry of Strained Si/Ge Superlattices Grown by Magnetron Sputter Epitaxy
Authors: Guizzetti G. , Patrini M. , Sutter P. , Känel H. Von 
Published: April 2011

AbstractSpectroscopic ellipsometry was used to characterize several short-period SimGen strained superlattices grown on Si(100) substrates or on graded SixGel-x alloy buffers (strainsymmetrization) by magnetron sputter epitaxy, a novel technique with potential application to industry-scale production of epitaxial Si/Ge heterostructures. Ellipsometric spectra were analyzed within a multilayer model, which included an oxide overlayer, in order to derive the effective dielectric fimctions of the SLs. spectra cannot be simulated by a sequence of Ge+Si slabs and compared to those of the compositionally equivalent alloys showed noticeable differences which can be ascribed to a combination of strain and confinement effects. The results agree with experimental findings and theoretical predictions on analogous SLs grown by MBE, thus confirming the reliability of the used technique to produce good quality SLs.
Optical Characterization of AlxGal-xsb/GaSb Epitaxial Layers
Authors: Lernia S. Di , Geddo M. , Guizzetti G. , Patrini M. , Bosacchi A. , Franchi S. , Magnaninia R. 
Published: April 2011

AbstractSpectroscopic ellipsometry from 1.4 to 5 eV was used to systematically characterize epitaxial heterostructures AlxGa1-xSb/GaSb for different x concentrations (x≤0.5). The structures were grown by MBE at temperatures and beam equivalent pressure ratios which optimize their lowtemperature photoluminescence properties. Complex dielectric functions of AlxGa1-xSb versus x were derived, for the first time, from the ellipsometric spectra after mathematically removing the oxide overlayer effects. The spectra were analyzed with their second energyderivatives in term of standard analytical lineshapes: in particular the El, E1+Δ1 and E2 critical point energies, broadening and amplitude parameters were derived as a function of x. On this basis we verified that the energy-shift model is appropriate to interpolate for any x≤0.5, thus allowing a nondestructive optical diagnostic of layer thickness and composition of epitaxial heterostructures based on A1xGa1-xSb.
High Performance Of Gettering In Hydrogen Annealed Wafer
Authors: Takeda Ryuji , Hayashi Kenro , Tokuoka Fumio 
Published: April 2011

AbstractThis paper reports on the study of the gettering of nickel contamination in hydrogen annealed CZ-silicon wafers by using method of wet chemical analysis. According to the wet chemical analysis, we believe that the hydrogen annealed wafer is of high quality in the region beneath the surface (DZ) and has a higher gettering ability for nickel compared with conventional CZ wafers. This observation is also in agreement with our MOS C-t measurements.
High Density Plasma Diagnostics For Predictive Model Development
Authors: Eddy C. R. , Douglass S. R. 
Published: April 2011

AbstractHigh density plasmas are being increasingly employed in both the deposition of low temperature, high quality passivant films and for highly anisotropic, nanometer-scale pattern transfer. The high degree of control necessary in these processes emphasizes the need for a more complete understanding of the basic physical and chemical mechanisms involved. To this end, a wide range of diagnostic techniques have been employed to characterize electron cyclotron resonance microwave plasmas applied to the etching of semiconductors in both chlorine- and methane-based chemistries. In particular, vacuum ultraviolet spectroscopy has been employed to identify important reactants and, where feasible, measure plasma constituent temperatures (e.g., neutral temperatures range from 0.1–0.3 eV in these plasmas). Langmuir probes, microwave interferometry and microwave electric field probes are used to monitor plasma parameters as a function of process conditions and provide understanding of microwave power deposition. Mass spectroscopy is utilized to characterize the plasma flux incident on the substrate, in terms of mass signature and charge state distribution. This flux is largely ionic with a considerable degree of dissociation, highly appropriate for directional etching. Results from each of these diagnostics are incorporated into an evolving predictive model for highly anisotropic, nanometer-scale etching of semiconductors.
Characterization Of ZnGe(AsxP1-x)2 Crystals By Electrolyte Electroreflectance Spectroscopy
Authors: Angelov Mirko , Goldhahn Rüdiger , Nennewitz Olaf , Schün Silke 
Published: April 2011

AbstractThe influence of the material composition on the optical properties of the quaternary compound semiconductor system ZnGe(AsxP1-x)2 was studied for the first time. The crystals have been synthesized by direct solidification from a stoichiometric melt. X-ray diffraction measurements revealed a chalcopyrite type lattice for the quaternary compound. Closer examination by energy dispersive X-ray microprobe analysis yielded the exact element concentrations for the As and P components. Then electrolyte electroreflectance (EER) spectroscopy was used to determine the energies of the fundamental optical transitions as a function of the composition x. The analysis shows an approximately linear increase of the direct band gap with decreasing As content.Furthermore, the influence of the composition on the splitting and ordering of the three highest valence bands was investigated by polarization dependent EER measurements. The spectra for two samples with x = 0.42 and 0.77 allowed the determination of the spin orbit parameter Aso and the crystal field parameter Δ;cf by using the quasicubic model. The values were found close to calculated ones, obtained by the same model under the assumption of a precise linear dependence of the band gap on the composition x.
Hydrogen Assisted Remote Plasma Enhanced Chemical Vapor Deposition of Amorphous Silicon Nitride Films
Authors: Santos-Filho P. , Koh K. , Stevens G. , Lucovsky G. 
Published: April 2011

AbstractWe show that in the RPECVD process the addition of a small upstream flow of H2 gas, combined with the He injected into the plasma region of the reactor, promotes chemical exchange between H and D when the material was deposited from deuterated Silane and ammonia and densifies the a- Si:N:H network. We have deposited hydrogenated stoichiometric nitrides with and without H2 injected into the plasma region. For small H2 flows, the deuterated samples show Fourier transform infrared (FTIR) N-D and N-H stretching and bending modes that interchange their populations, as the total bonded hydrogen content in the films remain constant. The hydrogen assisted grown films show, for small H2 flows, a constant amount of bonded-H, an optical index of refraction n=1.85, and reduced etch rate.
Precision of Non-invasive Temperature Measurement by Diffuse Reflectance Spectroscopy
Authors: Wang Zhongze , Kwan Siu L. , Pearsall T. P. , Booth James , Beard Barrett T. , Johnson Shane R. 
Published: April 2011

AbstractWe demonstrate the use of diffuse reflectance spectroscopy as a non-invasive probe for measurement of temperature in real time on Si and GaAs substrates during semiconductor processing. Our results show that the standard deviation of the non-invasive optical technique is less than 0.7 °C for GaAs over the temperature range 50 °C < T< 600 °C with 5-second updates. These results support the notion that non-invasive optical temperature measurement can be used in semiconductor processing with a precision exceeding that of a thermocouple.
An Extended Kalman Filter Based Method for Fast In-Situ Etch Rate Measurements
Authors: Vincent T. L. , Khargonekar P. P. , Terry F. L. 
Published: April 2011

AbstractThe goal of this paper is the presentation of a new algorithm for determining etch rate from single or multiple wavelength reflectometry data. This algorithm is based on techniques from recursive nonlinear estimation theory — Extended Kalman Filtering. A major advantage of our algorithm is extremely high speed. Consequently, it can be used in real-time feedback control applications. The speed advantage also makes it a suitable candidate for full wafer high speed etch rate measurement.
Anomalous Kinetics of the Trapping Reaction in One Dimension Under Steady State Conditions
Authors: Lin Anna L. , Kopelman Raoul 
Published: April 2011

ABSTRACTWe study the A + B→B trapping reaction under steady state conditions for the case in which both A particles and traps(B) are mobile. Using Monte Carlo simulations, we follow the kinetic rate law in one dimension. Anomalies arise due to self-organization of the A particles, which results in a slower steady state reaction rate than is predicted classically. We find a partial order of reaction with respect to trap density of X = 2, and an overall order for the reaction of Z = 3.2. These results are in agreement with other works which predict an exponential rather than an algebraic decay law with respect to the A particle density.
Dynamics of Structural Recovery and Mechanical Response of Polymeric Liquids Near to the Glass Transition
Authors: Colucci D. M. , Schultheisz C. R. , Mckenna G. B. 
Published: April 2011

ABSTRACTResults from the NIST torsional dilatometer have indicated that after a temperature step from equilibrium, the volume (structure) and mechanical response (physical aging) can evolve at different rates, depending on the temperature history. The torsional dilatometer results have been modeled in two ways. First, it was assumed that the volume and mechanical response are governed by different clocks, with the principle of time-aging time superposition employed to evaluate an aging time shift factor atc from the torsional response, which was then compared to a structural shift factor aδ calculated from the evolution of the volume. These results were also investigated using a thermoviscoelastic model based on rational thermodynamics and configurational entropy; this model does not include an explicit assumption of separate time scales, but different time scales for the structure and mechanical properties appear to arise naturally from the formulation. The results from the thermoviscoelastic model show good qualitative agreement with the torsional dilatometer results, although more material data is needed to make an exact comparison.
Electrokinetic Phenomena in Porous Media
Authors: Pengra David B. , Wong Po-Zen 
Published: April 2011

ABSTRACTElectrokinetic phenomena, such as electroosmosis (fluid-flow induced by applied electric fields) and streaming potential (the complementary process) are known to exist in brine-saturated porous media, but are very difficult to measure. With modern instrumentation and an ac method, we can now determine these transport coefficients accurately, and use them to characterize the permeability k1, the effective throat radius Re, and the electric potential at the slip-plane, or ζ-potential. Our study shows that permeability can be determined by two different means: by combining the dc values of the streaming potential, electroosmotic pressure and conductivity; or from the frequency response of ac electroosmosis alone. The high sensitivity of the method allows us to measure k over the 0.1–10,000 millidarcy range with less than lOkPa applied pressure. This article reviews some of the basics of electrokinetics and describes our methods. We also discuss effects of brine salinity and possible effects due to the fractal nature of the pore surface.
ATR-FTIR Spectral Investigation of SO2-treated Soda-Lime-Silicate Float Glass
Authors: Senturk U. , Lee D. H. , Condrate R. A. , Varner J. R. 
Published: April 2011

ABSTRACTThe near-surface infrared spectral changes that occurred on a commercial soda-lime-silicate glass, which was heat treated in SO2/H2O/air atmospheres, were measured, in the region 1200 to 600 cm−1, using attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. Sets of spectra were taken at different angles of incidence of the infrared beam corresponding to successive penetration depths on the surface, hence, giving a surface spectral profile. It was found that the Si-O-Si vibrational band, observed in the region ∼1100 cm−1, is the most affected; with increasing depth the band becomes weaker, depending on the treatment temperature and water content in the treatment atmosphere. The two different sides (the side in contact with the tin bath (tin side) and the opposite side (air side)) were determined to have a different character as a result of the dealkalization treatments.
Electrical Conduction in Relation to Local and Intermediate Range Structure of Rubidium Germanate Glasses
Authors: Jain H. , Kamitsos E. I. , Huang W. C. , Yiannopoulos Y. D. 
Published: April 2011

ABSTRACTThe dependence of dc electrical conductivity of a series of rubidium germanate glasses on rubidium oxide concentration is correlated with the structural information obtained from extended x-ray absorption fine structure analysis, density, x-ray photoelectron, Raman and far infrared absorption spectroscopy. Previously macroscopic molar or excess volume showed the most obvious correlation with the activation energy of conductivity. The present results demonstrate additional importance of the intermediate range structure.
Dynamic Aspects of Frenkel Defect Formation in Silver Chloride and Silver Bromide
Authors: Wilmer D. , Funke K. , Lauxtermann T. , Bennington S. M. 
Published: April 2011

ABSTRACTComplete ionic conductivity spectra have been taken of solid silver chloride and silver bromide at various temperatures. The spectra contain two new dynamic features: i) a thermally activated Debye-type relaxation which is explained by the frequent hopping of silver ions from their regular lattice sites to adjacent interstial sites and back again, and ii) conductivity maxima at about 500 GHz which are attributed to high-amplitude individual vibrational motions, mostly of the silver ions. – We also report results of a neutron scattering study on silver bromide. These contain thermally activated quasielastic contributions caused by the localized cation back-and-forth hopping and also give evidence of fast correlated movements of neighboring ions.
Study of Chemical Compatibility and Interfacial Resistance Between Oxide Cathode Materials and A LaGao3 –Based Electrolyte for Solid Oxide Fuel Cells
Authors: Wang Weitung , Hellstrom Eric. E. 
Published: April 2011

ABSTRACTThe chemical compatibility of (La0.6Sr0.4)MnO3 (LSM), (La0.6Sr0.4)CoO3 (LSC), (La0.6Sr0.4)(Co0.2Fe0.8)O3 (LSCF), and (La1.7Sr0.3)CuO4 (LSU) as cathode materials with the oxygen conductor (La0.9Sr0.l)(Ga0.8Mg0.2)O3-δ (LSGM) was studied. The interfacial resistance between the cathode materials and LSGM was measured using AC impedance spectroscopy. The same studies were done with yttria-stabilized zirconia (YSZ) electrolyte. The results showed that no new compounds formed between LSGM and the cathode materials LSM, LSC, and LSCF up to at least 1200°C; however, a solid solution formed between the materials. With YSZ, only LSM did not form new compounds, and no solid solutions formed. The interfacial resistance was much lower between all the cathode materials and LSGM than YSZ. The lowest interfacial resistances were for LSC/LSGM and LSCF/LSGM, which are suggested for medium temperature solid oxide fuel cells.
Segmental Relaxation in Crosslinked Rubber
Authors: Roland C. M. , Bero C. A. , Ngai K. L. , Antonietti M. 
Published: April 2011

ABSTRACTStudies of the local segmental relaxation in rubbery networks reveal a variety of behaviors. In experiments on networks with labeled junctions, whereby the motion of the crosslink site is specifically monitored, the segmental relaxation function broadens, accompanied by a larger activation energy, in a manner well-described by the coupling model of relaxation. The more usual experiment simply measures bulk relaxation, without discriminating among different relaxing entities. For networks, crosslinking introduces a distribution of relaxation behaviors, related to the proximity of a moiety to the junctions. The resulting inhomogeneously broadened relaxation function is difficult to analyze; nevertheless, a heightened sensitivity to temperature (larger activation energy) is exhibited, from which inferences can be made regarding the shape of the relaxation function. Finally, the segmental relaxation of highly crosslinked microgels is ostensibly homogeneous. Interestingly, however, the inverse correlation between the stretch exponent, β, and the activation energy, observed quantitatively in conventional networks, is violated by the microgels.
Effective Transverse Electrical Permittivities of Plain Weave, Twill Weave and Satin Fabric Composites
Authors: Chou T.-W. , Ning Q-G. 
Published: April 2011

ABSTRACTThis paper reports the analytical prediction of effective transverse electrical permittivities of plain weave, twill weave, 4-harness irregular satin, as well as 5-harness and 8-harness satin fabric composites with lossy constituents. Analytical solutions of the effective properties are presented. Numerical examples are given to illustrate the effects of fiber volume fraction and fabric architecture on the composite effective transverse dielectric behavior. Key words: electrical permittivity, plain weave, twill weave, satin weave, fabric composite, analytical solution.
Rigorous Link Between the Electrical and Mechanical Properties of Composite Materials
Authors: Torquato S. , Gibiansky L. V. 
Published: April 2011

ABSTRACTCross-property relations that link rigorously the effective electrical conductivity (or dielectric constant) and the effective elastic moduli of two-phase, isotropic composite materials are discussed. The cross-property relations can be optimal in some cases, i.e., they are realized by particular microstructures. The relations are applied to specific two-phase composites as well as to cracked media.
Dielectric Sensors Used in Environmental and Construction Engineering
Authors: Hilhorst M. A. , van Breugel K. , Pluimgraaff D. J. M. h. , Kroesea W. Stenfert 
Published: April 2011

ABSTRACTDielectric properties of materials can give insight into the microstructure or concentrations of their constituents and can be determined by measuring the complex impedance of a capacitor formed by a set of electrodes with the material as the dielectric. Measuring frequencies between 1 MHz and 1 GHz appeared to be most informative for soil and concrete. A new dielectric sensor containing an integrated circuit that includes all analog and digital circuitry is described briefly. This sensor is used to demonstrate the potential of dielectric sensor technology for applied materials research in the field in two recently developed applications. One application concerns the determination of the state of hardening of young concrete. The relationship shown is between changes in the dielectric properties and changes in the structure for curing concrete. The other application is a dielectric probe for contaminated site investigation. It appeared to be possible to locate chemically polluted soil layers, such as with chlorinated solvents or oil, using small changes in their dielectric properties.
Formation Features and Electrochemical Behavior of Porous Electropolymeric Films
Authors: Kolzunova L. G. , Kovarskii N. Ya 
Published: April 2011

ABSTRACTSome features of electroinitiated potentiostatic formation of polymeric films on the cathode in aqueous acrylamide/formaldehyde/zinc chloride and the electrochemical behavior of polymer modified electrode Pt/film have been studied through their voltammetry and impedance characteristics. The mechanism and kinetics of electrochemical depolarizers have been examined on Pt and Pt/film cathodes. The diffusion character of depolarizers and facilitated Red/Ox reactions on the modified Pt electrode were established.
Analysis of Immittance Spectroscopy Data: Model Comparisons, Universality?, and Estimation of Distributions of Activation Energies
Authors: Macdonald J. Ross 
Published: April 2011

ABSTRACTImmittance spectroscopy [IS] involves the measurement of the small-signal frequency response of dielectrics, semiconductors, electrolytes, biological cells, and polycrystalline, amorphous, and single-crystal electrically conducting materials. Analysis of such data to provide insight into the detailed, microscopic, physicochemical processes present in the full electrode and bulk material system is a crucial part of IS. Background information on IS and a discussion of its strengths and weaknesses are presented. The use of weighted, complex, nonlinear-least-squares for direct data fitting and for the solution of the ill-posed inversion problem of estimating continuous distributions of activation energies for important response models and for experimental data is illustrated. Replacements for the widely used, but incorrect, complexelectric- modulus data-analysis relations proposed long ago by C. T. Moynihan and associates for disordered ionic conductors, are presented and discussed. Recent proposals for various kinds of universal response behavior are examined and found to be unjustified. The present analysis methods are illustrated by applying them to 24°C data on a lithium aluminosilicate glass and to data over a wide temperature range on single-crystal CaTiO3:30%Al3+
Characteristics of Preliminary Waste Forms for Icpp Low Activity Waste (Law) Fractions after Radionuclide Separations
Authors: Vinjamuri Krishna 
Published: April 2011

AbstractCurrently, at the Idaho Chemical Processing Plant (ICPP) there are about 6800 m3 of liquid sodium-bearing and liquid high-level wastes (HLW), and 3800 m3 of solid calcined HLW. One of the waste processing options under consideration includes separation of the HLW into high activity and low activity (LAW) wastes, followed by immobilization. Preliminary glasses were synthesized for the sodium-bearing, alumina-bearing, and the zirconia-bearing LAW fractions after radionuclide separations. The glasses were formed by crucible melting of a mixture of reagent chemicals representative of the LAW waste streams and frit additives at 1200 °C for 5 hours, followed by overnight annealing at 550 °C and furnace cooling of the melt. These glasses were characterized for density, elastic property, viscosity, chemical durability, structural parameters, and glass phase separation. The results are compared with that of the Hanford's standard glass ARM-i, Savannah River's benchmark glass EA, and the ICPP's grout waste form prepared using the simulated non-radioactive sodium-bearing waste fraction.