bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combine spectroscopic ellipsometry and grazing x-ray reflectance for fine characterization of complex epitaxial structures
Authors: Boher P. , Stehle J. L. 
Published: April 2011

AbstractMSpectroscopic Ellipsometry (SE) and Grazing X-ray Reflectance (GXR) techniques are applied on different III-V epitaxial structures in order to extract accurately their structural information. Thickness information are obtained directly from Fourier transformation of the GXR spectra and confirmed by simulation of the reflectance curve. Compositions are deduced from SE regression using GXR thickness as input values. Examples on monolayer and bilayer structures are first remembered. Then the potentiality of the method is demonstrated to more complex systems (multilayer mirrors and HEMT structures).
Ge-Related Interfacial Defects In SiGe Alloy Structures
Authors: Macfarlane Patricia J. , Zvanut M. E. , Carlos W. E. , Twigg M. E. , Thompson P. E. 
Published: April 2011

AbstractThis paper reports etching results supporting the identification of the SG1 center as a germanium dangling bond defect at the interface between an oxide and crystalline SiGe. The presence of this defect is significant because, like an analogous center in Si-based systems, it may alter the operation of any microelectronic or micro-optical device which incorporates an interface between SiGe and an overlying oxide. The samples examined are oxygen implanted SiGe layers in which the SG 1 center is believed to occur at the interface between oxide precipitates and SiGe. Because of the center's apparent relation to the oxide precipitates distributed through layers of the sample, a depth profile assists in confirming the interfacial nature of the defect. We obtain a depth profile by comparing electron paramagnetic resonance (EPR) spectra of samples etched to decreasing thickness. EPR spectra indicate that the SG1 center decreases with depth in a manner that when correlated to a cross sectional transmission electron micrograph confirms the association with Si0 2 and supports its location at the SiGe/SiO2 precipitate interface.
Process Diagnostics For Remote Plasma-Enhanced Chemicalvapor Deposition (Pecvd) Of Silicon Nitrides
Authors: Banerjee A. , Lucovsky G. 
Published: April 2011

AbstractHydrogenated silicon nitride films were deposited in a remote plasma reactor using a plasmaexcited NH3/He mixture, and with downstream injection of SiH4. An electrically biased grid placed between the plasma tube and the deposition region was used to control the extent of the plasma afterglow into the deposition region. In situ monitoring by mass spectrometry (MS) indicated that the Si content of the film was increased when charged species were transported from the plasma region to the deposition region of the chamber, and that the properties of the resulting films could be understood in terms of two different deposition pathways, driven respectively by neutral, and a combination of neutral and charged precursor species.
Simultaneous Spatially Resolved Multispectral Optical Emission Of Sputter Processes
Authors: Klein J. D. , Clauso S. L. 
Published: April 2011

AbstractAn optical spectroscopy system was configured to monitor several plasma positions at the same time. The system allows monitoring of several points within a single plasma. Magnetron sputtering of YBa2Cu3O7 (YBCO) in a reduction-oxidation (redox) environment provided a process in which both cation and gas species are vital in determining the quality of the product film. Spatial sampling of the sputter plasma defined a disparity in the manner in which Ba and Cu emissions respond to changes in chamber gas composition. Oxygen emissions were found to respond quickly to inlet gas composition while Cu emissions were notably sluggish.
Non-Classical Reaction Kinetics: Experiments
Authors: Kopelman Raoul , Lin Anna L. 
Published: April 2011

ABSTRACTIt has been well established by theory and simulations that the reaction rates of diffusion-limited reactions can be affected by the spatial dimension in which they occur. The types of reactions A + B → C, A + A → A, and A + C→, C have been shown, theoretically and/or by simulation, to exhibit non-classical reaction kinetics in low and fractal dimensions. We present here experimental results from several 1D and fractal systems.An A+B → C type reaction was experimentally investigated in a long, thin capillary tube in which the reactants, A and B, are initially segregated. This initial segregation of reactants means that the net diffusion is along the length of the capillary only, making the system effectively 1D and allowing some of the properties of the resulting reaction front to be studied. The reaction rate of excitonic fusion, A + A →A, as well as trapping, A + C→ C, reactions were observed via phosphorescence(P) and delayed fluorescence(F) of naphthalene within the channels of Vycor glass, in isotopically mixed naphthalene crystals and in the isolated chains of dilute polymer blends. In these experiments, the non-classical kinetics are measured in terms of the heterogeneity exponent, h, from the equation: Rate ∼ F =; kt-hpn,, which gives the time dependence of the rate coefficient. Classically h =; 0, while h =; 1/2 in 1D, as well as in the fractal dimensions discussed here, for A + A → A as well as A + C →C type reactions.
Dynamic Light Scattering in 5CB Confined in Disordered Porous Media
Authors: Aliev Fouad M. , Nadtotchi Vladimir V. 
Published: April 2011

ABSTRACTWe performed dynamic and static light scattering measurements in nematic LC (5CB) confined in silica porous glasses with average pore sizes of 1000 A˚ (volume fraction of pores 40%) and 100 A˚ (27%). The experiments show significant changes in physical properties of confined LC. Nematic-isotropic phase transition temperature TNIis depressed by 0.6°C in 1000 A˚ pores compared to that bulk value and this phase transition was not detected at all in 100 A˚ pores. We found that even about 20°C below bulk melting temperature the relaxational processes in confined LC were not frozen. Slow relaxation process which does not exist in the bulk LC and wide spectrum of relaxation times (10−8–)s appear in both 100 A˚ and 1000 A˚. In 100 A˚ pores slow relaxation exists even at T corresponding to the bulk isotropic phase. Our data can not be described using the standard form of dynamical scaling variable (t/r) but they obey activated dynamical scaling with the scaling variablex= lnt/lnr.
Relaxational Dynamics and Strength in Supercooled Liquids from Impulsive Stimulated Thermal Scattering
Authors: Yang Yongwu , Muller Laura J. , Nelson Keith A. 
Published: April 2011

ABSTRACTImpulsive stimulated thermal scattering (ISTS), a time-domain light scattering technique, provides a more than 6-decade time range from sub-ns to many ms. It permits characterization of the structural relaxation dynamics and determination of the relaxation strength or Debye-Waller factor in supercooled liquids, and thus allows testing of the mode coupling theory of the liquidglass transition. ISTS experiments were performed on glass formers salol, butylbenzene, and the molten salt [Ca(N03)]0.4[KNO3]0.6. The relaxational dynamics and the Debye-Waller factorfq=0 were obtained. A square-root anomaly was observed in fq=0 (T) at a crossover temperature Tc for all three materials, consistent with the prediction of mode coupling theory.
Simulation of Dynamics of Liquid-Glass Transition
Authors: Kogure Y. , Kunitomi K. , Nakamura Y. , Doyama M. 
Published: April 2011

ABSTRACTGlass transition of of copper is simulated by the molecular dynamics method. Embedded atom method potential is used. The glass state was produced by quenching the liquid sample, which was produced by melting a crystal. The split second peak in RDF was observed in the glass state.
Enthalpy Relaxation Near the Glass Transition of a Supercooled Liquid [Ca(NO 3) 2]0.4[KNO3]0.6
Authors: Moon I. K. , Jeong Yoon-Hee 
Published: April 2011

ABSTRACTWe have investigated the slow dynamics in the glass transition region of a supercooled liquid [Ca(NO3)2]0.4[KN3]0.6 by measuring the dynamic specific heat in the frequency range from 0.01 Hz to 5 kHz. The equilibrium dynamics of the system in this range is well described by the stretched exponential function, exp[-(t/τ)β], and the Vogel-Fulcher type relaxation time, τ = τ0exp[Δ/(T − T0)].
Variation of the Structural Unit in Tellurite Glasses
Authors: Suehara Shigeru , Yamamoto Kazuo , Hishita Shunichi , Aizawa Takashi , Inoue Satoru , Nukui Akihiko 
Published: April 2011

ABSTRACTWe show that the variation of the structural unit in tellurite glasses is due to the charge transfer from modifier atoms to TeO6 octahedra with use of first-principles molecular orbital calculations. Orbital overlap population analysis reveals that the transferred electrons to the Te- O antibonding orbital cause breaking Te-O bonds and lead to reducing the coordination number of the Te atom.
Localization of Electrons and Acoustical Phonons in Irregular or Fractal Crystallites
Authors: Sapoval B. , Russ S. 
Published: April 2011

ABSTRACTThe behavior of electron and phonon excitations in systems with irregular boundaries is discussed on the specific example of prefractal shapes. We show that both electron states and acoustical phonons exhibit localization properties. This effect is stronger when the fractality of the shape is increased. In consequence the electron-phonon interaction in small crystallites should be strongly dependent on their shape or roughness. This localization could play a role in the thermal properties of glasses where internal partial crytallization has no reason to build pseudo-crytalline entities which should be smooth.
A Model for Ion-Sputtering: from Pattern Formation to Rough Surfaces
Authors: Cuerno R. , Makse H. A. , Tomassone S. , Harrington S. T. , Tanley H. E. 
Published: April 2011

ABSTRACTMany surfaces eroded by ion-sputtering have been observed to develop morphologies which are either periodic, or rough and non-periodic. We have introduced a discrete stochastic model that allows to interpret these experimental observations within a unified framework. A simple periodic pattern characterizes the initial stages of the surface evolution, whereas the later time regime is consistent with self-affine scaling. The continuum equation describing the surface height is a noisy version of the Kuramoto-Sivashinsky equation.
A Growth Model For Ramified Electrochemical Deposition
Authors: Marshall Guillermo , Mocskos Pablo , Olivella Martin 
Published: April 2011

ABSTRACTWe introduce a macroscopic model for the description of growth pattern formation in ramified electrochemical deposition. The theoretical model is formulated as a 2D time-dependent problem consisting in the Nernst-Planck equations for the concentration of the solute (cations and anions), coupled to a Poisson equation for the electrostatic potential and the Navier-Stokes equations for the solvent, with a moving boundary. A dimensional analysis is performed and a new set of dimensionless numbers governing the flow regime is derived. A 2D discrete version of these equations in a DBM scheme with a random moving boundary constitutes the computational model. We present numerical results which show that our growth model, with a proper variation of the set of dimensionless numbers, gives a reasonable picture of the interplay of the electroconvective, migration and diffusive motion of the ions near the growing tips.
Dehydration of Fractal Particles of Iron (III) and Aluminum Hydroxides
Authors: Vertegel A. A. , Kalinin S. V. , Oleynikov N. N. , Tretyakov Yu. D. 
Published: April 2011

ABSTRACTThe kinetic behavior of Fe(OH)3 and AI(OH)3 powders during thermal dehydration is investigated. It has been shown that the dehydration rate is governed by the value of fractal dimension of the sample without any respect to the nature of metal atom in hydroxide. The quantitative model for dehydration of fractal particles with particular value of fractal dimension is suggested. Theoretical predictions are in a good agreement with experimental data.
Influence of Spatial Correlations on Permeability and Connectivity of Sandstone
Authors: Makse Hernan A. , Havlin Shlomo , King Peter R. , Stanley H. Eugene 
Published: April 2011

ABSTRACTSedimentary rocks have complicated permeability patterns arising from the geological processes that formed them. Here we address the longstanding question of how such patterns are generated. We also analize data on two sandstone samples from different geological environments, and find that the permeability fluctuations display long-range power-law correlations characterized by an exponent H. For both samples, we find H ≈ 0.82 – 0.90. These permeability fluctuations significantly affect the flow of fluids through the rocks.
Microhydrodynamics with Dissipative Particle Dynamics
Authors: Español Pep , Zúñiga Ignacio 
Published: April 2011

ABSTRACTDissipative particle dynamics is essentially a coarse-grained molecular dynamic simulation technique that captures the essential physics with considerably less computer effort. We have given a sound theoretical foundation to the technique with respect to the equilibrium and hydrodynamic properties. In this paper we further explore the connection of the model parameters of DPD with the underlying microscopic dynamics for the case of a simple model of a solid. This provides some insight into the difficulties of interpretation of DPD simulations.
Critical Behavior in the Ultrasonic Properties of Suspensions
Authors: Esquivel-Sirvent R. , Green D. H. 
Published: April 2011

ABSTRACTVelocity and attenuation measurements of compressional waves at 3 and 5 MHz are presented for suspensions made of 1μm size particles of kaolinite or glass beads in water or light oil. At a critical concentration of 40%, the attenuation shows a sharp peak in attenuation as well as a sudden change in velocity. This behavior is observed in all suspensions and is independent of frequency or particle geometry. The observed behavior is consistent, with the excess attenuation induced by the fluid-shearing between particles. This behavior is the first experimental evidence for the existance of the freezing point, predicted by computer simulations.
Microstructure and Phase Characterization of the Surface of a-C:H Films by Means of Scanning Tunneling Microscopy and Spectroscopy
Authors: Rusman I. , Klibanov L. , Ben-Jacob E. , Croitoru N. 
Published: April 2011

ABSTRACTScanning Tunneling Microscopy and Spectroscopy (STM/STS) are used for obtaining nano-scale information on morphological and electronic properties of the surface of diamond-like amorphous hydrogenated carbon (a-C:H) filns. The films are prepared by rf plasma decomposition of methane CH4.A two phase model of a-C:H is suggested - sp3 bonded matrix in which sp2 clusters are embedded. A novel method of mapping graphite-like clusters over a-C:H surface is proposed. Tunneling I/V characteristics with a gap acquired on indium tin oxide (ITO) deposited on a-C:H indicate location of sp2 regions at the surface of a-C:H below an ITO overlayer
Complex Impedance Analysis of Silica Surface Film on Molybdenum Disilicide
Authors: Lin Wen-Yi , Gerhardt Rosario A. , Speyer Robert F. 
Published: April 2011

ABSTRACTThe exposure of molybdenum disilicide to combustion products at 1370° and 1600°C for 1 and 60 hours led to the formation of a silica surface film. The thickness of this protective layer, ranging from 4.4–18.2 μm, increased with temperature and exposure time. However, the dielectric constant (3.16) of the thin film was independent of ac field frequency, exposure time, and temperature, according to complex impedance analysis in the frequency range of 500 Hz to 1 MHz. MoSi2 specimens with a silica coating on one side resembled, in impedance spectroscopy terms, a resistor of low resistivity (MoSi2, 10−4 Ω·cm) in series with a parallel RC circuit of high resistivity (SiO2, 3.0×1010 Ω·cm). From this analysis, a calibration curve was generated for converting measured capacitance to silica film thickness. Relaxation time (on the order of 0.1 sec) and relaxation frequency (on the order of 1–10 Hz) were also derived, with the aid of semicircular regression of the complex impedance curves.
Numerical Impedance Analysis of Groove Electrodes In Aconducting Solution
Authors: Matsui H. , Kunugi A. 
Published: April 2011

ABSTRACTThe effect of electrode surface unevenness on electrode impedance was examined at rectangular groove electrodes by numerically solving the Laplace equation. CPE behavior appeared for the double-layer charging at considerably large groove electrodes in the absence of outer solution layer at high frequencies. This behavior originated from the current concentration to the upper portions of the groove. In the presence of an outer solution layer, the current concentration was greatly weakened by the series connection of solution resistance, resulting in the disappearance of CPE behavior. The real part of the impedance at high frequencies was not additive in the presence of exposed electrode surfaces outside the groove. The origin of no impedance additivity was discussed based on equipotential-amplitude data.
Quartz Crystal Microbalance for the Transient Study of Electrode Processes
Authors: Daujotis V. , Raudonis R , Kubilius V. , Gaidamauskas E. , Sližys R. 
Published: April 2011

ABSTRACTA technique for the measurement of quartz supported electrode oscillation frequency with special reference to transient electrochemical experiments was prepared. Due to changes in solution viscosity and density and in surface roughness during potential step experiments, the error in calculation of mass changes from frequency responses can reach 3–5 %. Initial deviation of electron numbers from unity by 30–60% during pulse electroreduction of dicyanoargentate shows that this process is not a simple faradaic reaction.
Characteristics of Ni/Nd-Doped Ceria Anode For Solid Oxide Fuel Cell
Authors: Nagamoto H. , Kumagai K. , Murayama H. 
Published: April 2011

ABSTRACTA fuel electrode consisting of particles of Ni and mixed conductor, Nd-doped ceria (NDC) has been developed. The electrode resistance decreased with decreasing the oxygen partial pressure lower than 10−11 atm, where the electronic conduction is predominant for NDC. This decrease in the resistance could be attributed to an increase in the triple phase boundary caused by an increase in electronic conductivity of NDC.
Experimental Limitations In Impedance Spectroscopy of Materials Systems
Authors: Hsieh G. , Edwards D. D. , Ford S. J. , Hwang J.-H. , Shane J. , Garboczi E. J. , Mason T. O. 
Published: April 2011

ABSTRACTUsing resistor-capacitor networks, sources of experimental artifacts in impedance spectroscopy were investigated, such sources include machine limitations, rig/cabling contributions at high frequencies, and artifacts due to high impedance reference electrodes and their geometrical placement. In the instance of electrode placement, computer simulations with a pixel-based model were in agreement with the experimental observations. Remedies for these artifacts such as rig shielding/grounding, geometrical adjustments, and null corrections are also discussed.
Evaluating the Microstructure of Conductor-Insulator Composites using Effective Media and Percolation Theories
Authors: McLachlan David S. 
Published: April 2011

ABSTRACTThe widely used Bruggeman symmetric and asymmetric media equations and the Clausius-Mossetti approximation are presented, and the idealized microstructures characterizing these media are examined.The percolation equations for the conductivity (σm) and complex dielectric constant (ɛm = ɛrm + iɛim) for ideal perfect conductor–conductor and conductor–perfect insulator continuum media (and lattices) are then introduced. The parameters characterizing the microstructure in the percolation equations are a critical volume fraction or percolation threshold (φc) and two exponents (t&s). The equations characterizing the crossover region, which occurs whenever the ratio of the conductivities of the two components is finite, or dielectric measurements are made, are also introduced. A general effective media equation, which has the same parameters as the percolation equations is noted, and its success in obtaining φc, when the ratio of the conductivities is finite, examined.The microstructures that allow φc to have values between a few percent and over 60%, as well as the occurrence of non–universal values of t, will also be discussed.
Dielectric Relaxation in Composite Systems
Authors: Mopsik Frederick I. 
Published: April 2011

ABSTRACTDielectric relaxation phenomena have contributions from both the internal reorientation modes of the molecules comprising a material as well as the details of how those modes couple together to form the material. This behavior can change quite sensitively with changes in the composition of material. For a composite material that has more than one phase, the presence of phase boundaries and even shape can play an additional and large role in the observed relaxation behavior. Analysis of the relaxation spectra can be used to study these effects. Examples are shown, primarily of polymeric materials, ranging from liquid solutions to phase separated mixtures to show how dielectric relaxation over a wide frequency range can be used to characterize and study composite materials.
Evaluation of 0-3 Ceramic/Ceramic Piezoelectric Composites by Dielectric Methods
Authors: Sayer M. , Mcintyre D. S. , Beckett J. , Barrow D. A. , Tandon R. 
Published: April 2011

ABSTRACTPiezoelectric composites prepared by firing ceramic lead zirconate titanate (PZT) powders within a PZT sol gel have a two phase structure in which both phases have high permittivity. Dielectric measurements reflect the presence of the two phases and of interfacial layers between the phases and at the electrodes. The system has been modelled as a) a composite dielectric and b) a multi-layer capacitor with some complex components. The frequency dependent response of composites, sol gel derived films and a bulk ceramic is compared.
Impedance Spectroscopy Of Biological Cells
Authors: Schmukler Robert E. 
Published: April 2011

ABSTRACTA six-electrode impedance chamber is used to perform wide-bandwidth (10 Hz − 3 MHz), sensitive impedance measurements to evaluate the electrical properties of living cells under normal physiologic conditions. The high sensitivity in these measurements, compared to cell suspension techniques, is accomplished by embedding the cells into the pores of a filter, creating a “pseudoepithelium” and markedly reducing the current shunt pathways around the cells. The shunt resistance for each cell is between 6 − 7 × 107 Ω. The cellular geometry and the portion of cell membrane under measurement are precisely controlled in this method. This technique produces a multi-parallel, whole-cell, patch-clamp like structure for 3.3 × 105 cells. The advantages of this technique, general insights, and improvements in impedance measurements will be discussed. Effects of bandwidth mismatch between high-input impedance amplifiers, reference point drift due to solution resistivity changes, and the use of porous electrodes will be covered. Lastly, the ability to electroporate the cell membrane contributes another unique way to study the impedance of living cells.