bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheed Intensity Observation of AlAs and GaAs by in situ Etching Using Arsenic Tribromide
Authors: Kaneko T. , Säger T. , Eberl K. 
Published: April 2011

AbstractThe first in situ layer-by-layer etching of AlAs(100) surfaces has been observed by using RHEED intensity oscillations technique and is contrasted with the results obtained for the etching of GaAs(100). The experiments were conducted by introducing the etchant, arsenic tribromide, directly into a conventional MBE chamber without the use of any carrier gas. RHEED intensity oscillations during the etching of AlAs are observed between 350 and 760°C indicating a continuous increase in the etching rate with temperatures, with no supply rate limiting conditions being reached. Conversely, oscillations from GaAs reveal a reaction rate limited region at low temperatures (≤500°C) and a supply rate limited region at higher temperature(>500°C). The maximum selectivity in the etching rates between GaAs and AlAs is obtained at 450°C (40:1). The selectivity, and the ability to monitor the layer-by-layer process by RHEED intensity oscillations is foreseen to be of great importance for more controlled fabrications of AlAs and GaAs heterointerfaces.
Growth and Characterization of Pseudomorphic Gel-yCy and Si1-yCy Alloy Layers on Si Substrates
Authors: Brunner K. , Eberl K. , Winter W. 
Published: April 2011

AbstractPseudomorphic Gel-yCy and Sil-yCy alloy layers have been synthesized by solidsource molecular beam epitaxy on Si (001) substrates. High quality short-period Gel-y Cy/Si superlattice structures with a carbon content up to about 5 % are grown at low substrate temperature. The partial compensation of strain within Ge964C036 layers of 7 Å thickness improves the thermal stability against lattice relaxation, compared to pure Ge layers. Band-edge related photoluminescence is observed from pseudomorphic Sil-yCy/Si multiple quantum well structures at low temperature. The two predominant luminescence lines are attributed to no-phonon transitions and Si-Si TO phonon replicas of bound excitons confined within the Sil-yCy alloy quantum well layers. The tensile strain within the Sil-yCy layers shifts the twofold degenerate Δ(2) conduction band valley down in energy and is mainly responsible for the linear band gap reduction which is observed for increasing C content.
Damage, Strain and Quantum Confinement Issues in Dry Etched Semiconductor Nanostructures
Authors: Tang Y. S. , Torres C. M. Sotomayor 
Published: April 2011

AbstractSemiconductor quantum wires and dots have been fabricated in GaAs/AlGaAs, CdTe/CdMnTe and Si/SiGe multiple quantum wells using electron beam patterning and reactive ion etching and studied by photoreflectance, photoluminescence and Raman scattering. It was found that the smaller the lateral size of the nanostructure, the smaller the fabrication induced residual strain. In all cases, the dominant strain component is found to be parallel to the sample growth direction, i.e., along the etched sidewalls of the etched wires and dots. The lateral confining potential is found to be quasi-parabolic for polar semiconductor systems. Possible ways of using and controlling the damage and residual strain in nanostructures are discussed in the context of device applications of nanostructures.
Afm/Tem Investigation of Low Temperature Polycrystalline Silicon Grown by ECR-CVD
Authors: Hsiao H. L. , Wang K. C. , Cheng L. W. , Yang A. B. , Yew T. R. , Hwang H. L. 
Published: April 2011

AbstractThe polycrystalline silicon films were deposited by electron cyclotron resonance chemical vapor deposition (ECR-CVD) with hydrogen dilution at 250°C and without any thermal annealing. The surface morphology and the microstructure of the poly-Si films are investigated by atomic force microscopy (AFM), plan-view transmission electron microscopy (TEM), crosssectional TEM and high resolution TEM (HRTEM). The low temperature poly-Si films deposited by ECR-CVD show a special leaf-like grain shape (plan-view) and an upside-down cone shape (3-dimensional view). The grains in the poly-Si films have preferred orientation of <112> and the longer side of the leaf-like grain is direction and the shorter side is direction. Lattice bending and interruption are found in the films. The arrangement of the atoms on the grains are well ordered, while atoms in the interfacial regions are randomly distributed. A simple grain formation model based on growth rate differences between different planes and etching effect can explain the film growth mechanism and the formation of the special grain geometry.
Room Temperature Contactless Electromodulation Characterization of a Wafer-Sized InGaAs/GaAs/GaAlAs Grinsch Laser Structure
Authors: Krystek Wojciech , Leibovitch M. , Pollak Fred H. , Gumbs Godfrey , Konopelski T. 
Published: April 2011

AbstractUsing contactless electroreflectance at 300K we have characterized the complete potential profile of a pseudomorphic 0.98 μm InGaAs/GaAs/GaAlAs graded index of refraction separate confinement heterostructure laser fabricated by molecular beam epitaxy. Signals were detected from all three relevant portions of the sample. Comparison of the observed transitions from the InGaAs single quantum well (SQW) section with an envelope function calculation (including the effects of strain) made it possible to evaluate the In composition and width of SQW. These values were in good agreement with the intended parameters. The energy of 11H, the fundamental conduction to heavy-hole level (which is closely related to the lasing frequency) can easily be determined to less than ± 1 nm at 300K. From the period of the observed Franz-Keldysh oscillations from the graded GaAlAs region it was possible to directly evaluate the built-in electric field in the structure.
Steplike Lineshape of Low Temperature Photoreflectance Spectra of InAlAs
Authors: Baltagi Y. , Bearzi E. , Bru-Chevallier C. , Benyattou T. , Guillot G. , Harmand J. C. 
Published: April 2011

AbstractWe have performed low temperature photoreflectance spectra on several MBE-InAlAs layers lattice matched to InP. Unusual lineshapes of PR spectra are observed at temperatures below 40K, characterized by a step at the InAlAs band gap energy. This step is shown to be related to a strong modification of the photo luminescence background of the photoreflectance spectra. This modification is attributed to an effect of carrier localization due to clustering effects in the InAlAs layers
Spectroellipsometry Studies of Znl-x.cdxSe: From Optical Functions to Heterostructure Characterization
Authors: Lee Joungchel , Hong Byungyou , Burnham J. S. , Collins R. W. , Flack F. , Samarth N. 
Published: April 2011

AbstractThe dielectric functions of 0.5–1.5 μm Znl-xCdxSe (0≤x≤0.34) epilayers on GaAs have been determined over the photon energy range 1.5≤E≤5.3 eV. These spectra have been parameterized using the Sellmeier approximation for energies less than the fundamental gap at E0 and using a sum of Lorentz oscillators above the gap region. As an example of the usefulness of the approach, expressions are provided that yield the index of refraction of Znl-xCdxSe (0≤x≤ 0.34) for 1.5 eV≤E<E0- As a second example, we have determined the composition and thickness of a Znl-xCdxSe quantum well between ZnSe barrier layers.
Monitoring Of The Intermediate Products In The Thermal Decomposition Of SiH4, Si2H6, SiF4 AND SiH2F2
Authors: Han Jae Hyun , Ryu Hyun-Kyu , Moon Sang Heup 
Published: April 2011

AbstractThermal decomposition of SiH4, Si2H6, SiF4 and SiH2F2 used as the reactants in the Si-CVD process was studied by monitoring the gaseous products with a quadrupole mass spectrometcr (QMS). The rates of SiH4 pyrolysis showed a large compensation effect at low pressures, which agreed with the theory of unimolecular reaction. Si2H6 decomposed at relatively low temperatures producing SiH4 as the intermediate products. The decomposition temperatures of the other compounds increased in the order of SiH4, SiH2F2 and SiF4. The pyrolysis rates of SiH2F2 and silanes, i.e., SiH4 or Si2H6, were enhanced synergically when they were mixed together. The results were explained by a reaction mechanism proposed based on analysis of the intermediates produced in the process.
Trace-Element Accelerator Mass Spectrometry: A New Technique for Low-Level Impurity Measurements in Semiconductors
Authors: Datar S. A. , Renfrow S. N. , Anthony J. M. , Mcdaniel F. D. 
Published: April 2011

AbstractSIMS is a well-established technique for the measurement of impurities in semiconductor materials. It is the technique of choice for the measurement of very low levels of impurities, especially depth profiles. Accelerator Mass Spectrometry (AMS) is also a well-established technique and is primarily used for measurements of abundance ratios of long-lived radionuclides, such as 14C and 36C1 to their respective stable isotopes. A combination of these techniques holds the potential for impurity determination in semiconductors at the ppt level. The new technique, Trace- Element Accelerator Mass Spectrometry (TEAMS), eliminates the problem of molecular interference which is the major constraint limiting the sensitivity of SIMS. Depth profiles for B, P and As implants in Si, obtained by TEAMS are presented below.
A Comparative Study of the Reflectance Difference Spectrum from Si(001) Using Reflectance Difference Spectroscopy /Low-Energy Electron Diffraction/Scanning Tunneling Microscopy
Authors: Lin Jia-Ling , Jaloviar S. G. , Mantese L. , Aspnes D. E. , McCaughan L. , Lagally M. G. 
Published: April 2011

AbstractFrom a comparative study using scanning tunneling microscopy, high-resolution lowenergy electron diffraction, and reflectance difference spectroscopy, we investigate the optical anisotropy on clean and H-covered Si(001) surfaces. We demonstrate a high sensitivity of reflectance difference spectroscopy to the surface tructural anisotropy and surface chemistry.
Photoluminescence and Raman Scattering from (CdSe)m,(ZnSe)n-ZnSe Multiple Quantum Wells Under Hydrostatic Pressure
Authors: Zhang J. Q. , Liu Z. X. , Wang Z. P. , Han H. X. , Li G. H. , Peng Z. L. , Yuan S. X. 
Published: April 2011

AbstractThe photoluminescence and Raman scattering of {|(CdSe)1 (ZnSe)3|14-(ZnSe)130} × 5 multiple quantum well structure have been investigated at 77 K and under hydrostatic pressure up to 7 GPa. Resonant excitations have been accomplished by turning the electronic levels under hydrostatic high pressure. Two kind of excitons and ZnSe-like LO phonon modes as well as their pressure behavior are presented.
Thermal Stability in Pd-Based Contacts to p-Type In0.53Ga0.47as Characterized by Rbs
Authors: Leech P. W. , Ressel P. , Reeves G. K. , Zhou W. , Kuphal E. 
Published: April 2011

AbstractThe resistivity and interfacial characteristics of Pd/Zn/Pd/Au and Pd/Zn/Au/LaBd6/Au contacts to p-In0.53Ga0.47As have been investigated. Annealing of the contacts at 375–425°C yielded a minimum in specific contact resistance, p,, of 2 × 10-7 Δ cm2 for the Pd/Zn/Pd/Au contacts and 1 Δ cm2 for the Pd/Zn/Au/LaB6/Au configuration. This is the lowest reported measurement of pc for an ohmic contact to p-In0.53Ga0.47As doped to ≤1 × 1019 cm−3. In the Pd/Zn/Au/LaB6/Au scheme, the minimum in pc was the same irrespective of whether the Zn was incorporated as a structural layer or as Zn ions implanted into the interfacial Pd prior to metallization. The effect of thickness of the Zn layer on pc has been determined for the Pd/Zn/Au/LaB6/Au scheme. RBS measurements have shown that during annealing, the LaB6 layer acted as a barrier to the indiffusion of Au and to the degradation of the In0.53Ga0.47As substrate.
Determining Thin Film Density by Energy-Dispersive X-Ray Reflectivity: Application to a Spin-On-Glass Dielectric
Authors: Wallace W. E. , Wu W. L. 
Published: April 2011

AbstractA novel method for determining thin film density by energy dispersive x-ray reflectivity is demonstrated for a polymer-derived spin-on-glass dielectric intended for microelectronics applications. The effects of sample misalignment limit the accuracy of x-ray reflectivity as typically practiced. These effects may be properly accounted for by measuring the critical angle for reflection at many different x-ray wavelengths simultaneously. From this measurement, thin film density can be ascertained with much improved accuracy. The results of the x-ray reflectivity measurement are compared to those derived from MeV ion scattering.
Optical Second Harmonic Generation Method For Silicon Material Monitoring And Characterization During Ion Implantation And Annealing Processes
Authors: Gu Y. , Chou Y. C. , Vu T. , Yen K. , Lin Y. S. , Li G. P. 
Published: April 2011

AbstractNon-linear optical second harmonic generation (SHG) from bulk silicon is very weak because of the inversion symmetry of the silicon lattice structure. However, when silicon material is subjected to the ion implantation and thermal annealing processes, the inversion symmetry will be broken. As a result, the optical second harmonic generation from the material will increase, and the characteristics of the second harmonic signal are related to the material conditions. In this study, we compare SHG results with Transmission Electron Microscope (TEM) observations for silicon material that has been treated with phosphorous ion implantation and rapid thermal annealing, and suggest that the SHG method may be used for the detection and monitoring of impurities and defects during ion implantation and thermal annealing processes.
Structural relaxations in a Simple Model Molten SaltM
Authors: Fuchs Matthias 
Published: April 2011

ABSTRACTThe structural relaxations of a dense, binary mixture of charged hard spheres are studied using the Mode Coupling Theory (MCT). Qualitative differences to non-ionic systems are shown to result from the long-range Coulomb interaction and charge ordering in dense molten salts. The presented non-equilibrium results are determined by the equilibrium structure, which is input using the well studied Mean Spherical Approximation.
A Low Frequency Study of the Vibrational Modes in Alkalisilicate Glasses by Raman Spectroscopy
Authors: Sommer R. , Toulouse J. , Jain H. 
Published: April 2011

ABSTRACTWe have performed a study on low frequency modes in several alkali silicate glasses by Raman spectroscopy. The Boson peak region is analyzed with a single parameter ω0 which is believed to characerize the density of states of the system. Analysis of the dependence of ω0 on the nature and concentration of the alkali suggests that the position of the Boson peak is essentially governed by the ratio “force constant” over “mass” of localized oscillator modes. At lower frequency (below 30 cm−1), the “excess” intensity can be explained by considering secondorder processes of the same vibrational modes, superimposed on other (possibly relaxational) modes.
Fractal and Non-Fractal Surfaces in Ion Sputtering
Authors: Barabási A.-L. , Cuerno R. 
Published: April 2011

ABSTRACTRecently a number of experimental studies focusing on the scaling properties of surfaces eroded by ion bombardment provided apparently contradictory results. A number of experiments report the observation of self-affine fractal surfaces, while others provide evidence about the development of a non-fractal periodic ripple structure. To explain these discrepancies, here we derive a stochastic nonlinear equation that describes the evolution and scaling properties of surfaces eroded by ion bombardment. The coefficients appearing in the equation can be calculated explicitly in terms of the physical parameters characterizing the sputtering process. We find that transitions may take place between various scaling behaviors when experimental parameters, such as the angle of incidence of the incoming ions or their average penetration depth, are varied.
Nonequlibrium Statistical Mechanics of An Ensemble of Vesicles
Authors: Golubović Leonardo 
Published: April 2011

ABSTRACTWe investigate far-from-equilibrium dynamics of a polydisperse ensemble of vesicles ( such as liposomes). For that purpose, we construct of a Smoluchowsky-type transport equation incorporating vesicle diffusion and the processes of vesicle fusions and fissions. This approach is used to study the time evolution of an initially monodisperse vesicle ensemble and its important quantities such as the internal aqueous, encapsulated volume. We find three stages of the evolution: (i) an early stage during which EV remains nearly constant, followed by (ii) a stage with a rapid decay of the EV, and, finally (iii) a late stage in which the ensemble approaches the thermodynamic equilibrium. In the far-fromequilibrium stages (i) and (ii), the vesicle ensemble is a “two-fluid” system composed of a polydisperse fluid of small, nearly equilibrated vesicles, coexisting with a fluid of nearly monodisperse vesicles which size evolves due to evaporation-recondensation of the small vesicles. Our picture agrees with experimental data on the EV of lecithin liposomes.
Atomic Kinetics and Dynamical Phason Disorder in a Quasicrystal
Authors: Dzugutov M. 
Published: April 2011

ABSTRACTSlow relaxation dynamics in strongly coupled systems is known to be universally described by the stretched exponential Kohlrausch law. However, this phenomenon, observed in various condensed systems, still eludes a comprehensive microscopic interpretation. I discuss here the relaxation dynamics in an equilibrium dodecagonal quasicrystal which demonstrates a pronounced stretched exponential behaviour. The quasicrystal, simulated by Molecular Dynamics, reveals the presence of dynamical phason disorder, a generic form of relaxation dynamics associated with incommensurate, or phason degrees of freedom. This dynamics brings about a novel form of atomic diffusion, which is examined here by calculating the self part of intermediate scattering function Fs(Q, t). The latter displays a non-exponential decay which is found to be described by the Kohlrausch law with the stretching exponent β = 0.47. I discuss here a possible similarity between the dynamics of quasicrystals observed and that of supercooled liquids and glasses.
Structure of Silane Films and their Adhesion Properties
Authors: Araujo Y. Carolina , Toledo Pedro G. 
Published: April 2011

ABSTRACTSilane films, their structure and stability, are of great interest in processes such as flow in porous media, mineral flotation, chromatography and corrosion. Here, the structure of octadecyl thriclorosilane (OTS) films on glass surfaces is studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM), their adhesion properties by contact angle measurements and adhesion tests. Complete glass surface coverage by the silane is attained after an immersion time tc characteristic of the OTS compound. The time evolution of the OTS films regarding surface coverage is monitored by SEM with a BSE detector, by measuring the OTS film thicknesses from XPS data, by AFM and by contact angle measurement. At tc the structure of the films changes from micromolecular to macromolecular. Below tc the glass coverage has a fractal geometry and various degrees of hydrophobicity are possible. At t > tc the surface coverage is complete and the contact angle achieved a well defined constant value.
Morphological changes of Branched Ge Clusters caused by Diffusion Fields and Surface Roughness of Au Underlayer
Authors: Sugawara A. , Kikukawa T. , Haga Y. , Nittono O. 
Published: April 2011

ABSTRACTThe formation of polycrystalline Ge clusters, during annealing of amorphous Ge/polycrystalline Au bilayers, has been studied by in-situ transmission and scanning electron microscopy. The experimentally observed generation of branching patterns, and the evolution mechanism of branches, are discussed on the basis of finite diffusion length aggregation simulations.
A Simple Model for Anomalous Relaxation in Porous Media
Authors: Araujo Mariela , Gonzalez Orlando 
Published: April 2011

ABSTRACTWe present a simple model to explain anomalous relaxation in random porous media. The model, based on the properties of random walks on a disordered structure, is able to describe essential features of the relaxation process in terms of a one body picture, in which the many body effects are approximated by geometrical restrictions on the particles diffusion. Disorder is considered as a random variable (quenched and annealed) taken from a power-law distribution |μ|ξμ−1. Quantities relevant to relaxation phenomena, such as the characteristic function and the particle density are calculated. Different regimes are observed as a function of the disorder parameter μ. For μ > 1 the relaxation is of exponential or Debye type, and turns into a stretched exponential as μ decreases. We compare numerical predictions (based on Monte Carlo simulations) with experimental data from porous rocks obtained by Nuclear Magnetic Resonance, and numerical data from other disordered systems.
Interaction Of Dilute Colloidal Particles In A Mixed Solvent
Authors: Maher James V. , Kurnaz M. Levent 
Published: April 2011

IntroductionColloidal particles in mixed solvents can show reversible aggregation in the one-phase regime of the mixture near the mixture's phase separation temperature [1–5]. This aggregation condition has been shown to be related to the affinity of the colloidal surfaces for one of the solvent components. In particular, for a 2,6 lutidine plus water (LW) mixture with colloidally dispersed polystyrene latex spheres (PLS) in a temperature range near the critical temperature, Tc, in the mixture's two-phase region, the particles will partition into one of the solvent phases, with the meniscus between the liquid phases clear to the eye and showing no sign of population by colloidal particles. Which phase of the solvent attracts the particles depends on the surface charge density of the particles, with high surface charge density particles preferring the water-rich phase and low charge density particles preferring the lutidine rich phase. As temperature is advanced deeper into the two-phase region (all effects discussed here are equilibrium effects), there is a temperature, Tw, at which particles appear on the meniscus (most particles remain in the preferred phase, whose population depletion is too small to measure). Tw changes with the surface charge density of the particles [4], but not with radius or with number density of the particles in the sample. The aggregation observed in the one-phase region [5] is then restricted to the side of the solvent's coexistence curve poor in the component which is rich in the partitioning-favored phase.
Immittance Data-Handling/Analyzing Criteria For Heterogeneous Systems
Authors: Alim Mohammad A. 
Published: April 2011

ABSTRACTThe factors determining electrical characteristics using immittance data of heterogeneous systems are not identical to those established with devices based on single-crystal/single-junction (SCSJ) technology. The ”state of normalization” using ”physical geometrical factors” of the asmeasured immittance quantities does not provide a SCSJ-like straightforward interpretation of simultaneously operative phenomena. The normalization procedure can the vitiate identity of each phenomenon occurring within the series-parallel microstructural network of electrical paths. The advantage of using the as-measured immittance data in delineating simultaneously operative phenomena is emphasized. An approach to data-handling/analyzing is proposed considering the limitations and conditions of utilizing the as-measured immittance data. The ”state of normalization” using ”physical geometrical factors” can only be executed for a specific type of phenomenon when isolated from the total electrical behavior.