bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tailored Si-Layers on Silicon Oxide Obtained by Thermal CVD
Authors: Beaucarne G. , Poortmans J. , Caymax M. , Nijs J. , Mertens R. 
Published: April 2011

AbstractIn this paper, a method to obtain by CVD Si layers on silicon oxide with the desired grain size is described, involving nucleation control through the growth parameters. Nucleation experiments are carried out with a hydrogen - dichlorosilane - HCl ambient at high temperature. The nucleus density is observed to drop to low values at a threshold HCl-flow. A qualitative explanation using concepts from atomistic nucleation theory is proposed. The effect of addition of diborane to the gas flow is investigated and appears to be small or non-existent . Finally, preliminary results of a thin-film crystalline silicon solar cell process applied on such layers are given to illustrate the potential of such layers.
Mbe Growth And Characterization Of Er/O And Er/F Doped Si Light Emitting Structures
Authors: Ni W.-X. , Du C.-X. , Joelsson K. B , Hansson G. V. , Pozina G. , Buyanova I. A. , Chen W. M. , Monemar B. 
Published: April 2011

AbstractBy using a low temperature growth process, Er doping in Si during MBE using Er2O3 or ErF3 as dopant sources has achieved a level of 5 × 1019 cm−3 without precipitation and generation of other extended defects. Luminescence properties of these Er-doped MBE Si structures have been extensively studied using both photon and hot electron impact excitation at a wide range of temperatures (2–300 K). It has been found that by incorporating C into Er/O doped layers, the room temperature EL emission with a FWHM value of 14 meV was ten times more intense than that with lower C doping. Post thermal annealing gave a strong effect on Er/F doped layers, leading to a 7-fold increase of the highest peak intensity while the peak line width reduced to 0.12 meV, which is very important for laser applications.
Resonant Excitation Spectroscopy of Light-Emitting Silicon Nanostructures
Authors: Kanemitsu Yoshihiko , Okamoto Shinji 
Published: April 2011

AbstractWe have studied optical properties and electronic structures of zero-dimensional (OD) Si nanocrystals and two-dimensional (2D) Si quantum wells by means of resonant excitation spectroscopy. Resonantly excited luminescence spectra of 0D Si nanocrystals are sensitive to the surface structure. The size dependence of the photoluminescence (PL) properties and resonantly excited PL spectra of SiO2-capped Si nanocrystals indicate that excitons are localized at the interface between the c-Si and SiO2 surface layer. The TO-phonon related structure in resonantly excited luminescence is clearly observed in H-passivated Si nanocrystals. Hpassivated Si nanocrystals show their crystalline nature, while the oxidized Si nanocrystals show their disordered nature. Luminescence properties of Si/SiO2 nanocrystals are similar to those of Si/SiO2 quantum wells. The electronic structures and luminescence properties of Si nanostructures are discussed.
Optical Activation of Erbium Doped Porous Silicon by Hydrogen Plasma Treatment
Authors: Dejima T. , Saito R. , Yugou S. , Isshiki H. , Kimura T. 
Published: April 2011

AbstractEr3+;-doped porous silicon (Er:PS) shows strong room temperature emissions at ˜ 1.54μm. However, its spectrum is usually much broader than that of Er-doped crystalline silicon (fullwidth at half maximum - FWHM - is ˜ 10 nm). It is probably because Er ions are located in amorphous phases. We report in this paper that strong and very sharp Er3+ 1.54μm emissions are obtained, when Er:PS samples are treated in a hydrogen plasma. Porous silicon layers are formed by anodic etching and then doped with Er3+ ions in an ErCl3/ethanol solution by an electrochemical method, and then treated in a hydrogen plasma at ˜ 1000°C from 0.5 min to 90 min for the optical activation. Several sharp peaks are observed at 20K, of which the strongest peak is located at 1.538 μm with an FWHM less than 1 nm. This value is comparable to that obtained from Er3+-doped crystalline silicon formed by means of molecular beam epitaxy (MBE) or ion implantation. Comparisons are made among hydrogen plasma, argon plasma, H2 flow and vacuum for the post-dope annealing atmosphere. Fourier-transform infrared (FT-IR) absorption and secondary ions mass spectrometry (SIMS) measurements are also carried out. We conclude that preferential etching of amorphous surface layers, and termination of dangling bonds of silicon nanocrystallites with hydrogen atoms and formation of Er-H complexes may be responsible for the strong and sharp Er3+-related luminescence.
Infrared Reflection Spectroscopy Of As-Anodized And Passivated 6H And 4H Porous Silicon Carbide
Authors: Spanier Jonathan E. , Herman Irving P. 
Published: April 2011

AbstractWe present a study of the infrared reflectance of porous silicon carbide (PSC) formed by the electrochemical dissolution of silicon carbide substrates of both 6H and 4H polytypes. The formation of porous silicon carbide from a 4H-SiC substrate is reported for the first time, as is the reflectance from n-PSC, both as-anodized and passivated. The passivation of PSC has been accomplished using a short thermal oxidation. Fourier transform infrared (FTIR) reflectance spectroscopy is employed ex situ after different stages of the thermal oxidation process. The characteristics of the reststrahlen band normally observed in bulk SiC are altered by anodization; further changes in the reflectance spectra occur following oxidation for different short periods of time. An effective medium theory model which includes air, SiC and SiO2 as component materials is shown to characterize the observed changes in the reflectance spectra after different stages of PSC oxidation.
Ion-Beam Synthesized Semiconducting β-FeSi2 Controlled By Annealing Procedures And Phase-Transitions
Authors: Maeda Y. , Fujita T. , Akita T. , Umezawa K. , Miyake K. 
Published: April 2011

AbstractThe ion beam synthesis (IBS) of β-FeSi2 was examined by Rutherford backscattering spectroscopy (RBS) and x-ray diffractometry (XRD), and the structural characterization was carried out by Raman spectroscopy and scanning electron microscopy (SEM). We found that the IBS of β- FeSi2 is controlled by two different processes depending on the annealing temperature (Ta) and Fe surface concentration (Cs); (I) precipitation of β-FeSi2 on the surface in Cs˜30 at% and Ta⩾700° C and (II) phase transition from γ -FeSi2 to β-FeSi2 in Cs<∼20 at%and Ta⩾600°C. The precipitation process(1) created large sized (-10 μm) polycrystalline grains of β-FeSi2. The good crystalline β-FeSi2 obtained above 800°C showed a clear reflectance maximum at 0.88 eV due to the optical transition at the direct band-gap of 0.84 eV observed in the characteristic plot ((ahv)2 vs. hv) of the optical absorption.
First-Principles Study Of Photoluminescence From Silicon/Silicon-Oxide Interfaces
Authors: Kageshima H. , Shiraishi K. 
Published: April 2011

AbstractExperimentally reported interfacial luminescence from silicon nano structures are studied by using a first-principles calculation of a Si(100) quantum slab covered with silicon oxide. When Si-OH bonds were introduced at the silicon/silicon-oxide interface, wave functions at the valence band top and near conduction band bottom localized vertically and laterally near the Si-OH bonds. Such strong localization is the result of the cooperation of the coupling of non-bonding 2p lone pair orbitals on interfacial 0 atoms and the strong dipole of OH. Furthermore, the localization is significant only in silicon nano structures. This localization of the wave functions can be the source for creating localized excitons, which can dramatically enhance the intensity of photoluminescence. Therefore, interfacial Si-OH bonds are a theoretically convincing possible source of reported interfacial luminescence.
Photoelastic Waveguides In Sige/Si Heterostructures And Bulk Si
Authors: Lea E. , Weiss B. L. , Rho H. , Jackson H. E. 
Published: April 2011

AbstractPhotoelastic waveguides in bulk Si and SiGe/Si heterostructures have been modelled and characterised. The calculated transverse strain profiles of photoelastic waveguide structures in SiGe/Si heterostructures and bulk silicon are in good agreement with those obtained by microRaman experiments. The waveguide characteristics are also found to be in good agreement with those obtained from the strain modelling and demonstrate that low loss waveguides can be fabricated using these structures
Quasi-Two-Dimensional Smectic States of DNA Molecules Intercalated between Lipid Membranes in Multi-Lamellar Phases
Authors: Golubović Leonardo , Moldovan Dorel , Golubović Mirjana 
Published: April 2011

AbstractWe study fluctuations of DNA-cationic lipid complexes in their lamellar membrane phases with DNA intercalated between lipid membranes. We theoretically elucidate this novel state of matter by characterizing it as the very first realization of adecoupled(unregistered) phase of strongly fluctuating 2-d smectic manifolds weakly interacting across membranes. Due to couplings between adjacent 2-d smectic Lx, × Lyplanes, the experimentally observed ordinary 2-d smectic behavior [Salditt et al., Phys. Rev. Lett. 79, 2582 (1997)] of DNA in-plane undulations, with, must cross over, at the longest scales, to a novel fluctuation behavior, with <u2> ˜ (logLy)2˜ (logLx.)2.
Self-Assembly of Tyrocidines in Nanotubular Structures
Authors: Thies M. , Paradies H. H. 
Published: April 2011

AbstractHollow tubular structures of tyrocidines, a cyclic decapeptide with two amino acids residues in the D-configuration and eight in the L-configuration, were formed in acid aqueous solutions in the presence of ethanol (20°C). Discrete nanotubes can be produced under controlled conditions, e.g. the amount of water added, or in the presence of protons from ethanol-water solutions (45/55 %v/v). These cyclic oligopeptides crystallize into tubular structures hundreds of nanometer long with an internal diameter of 9.0 Å and outer diameter of 35 Å. Support for the proposed tubular structure is provided by electronmicroscopy, SAXS and Fourier-transform infrared spectroscopy. These structures are open-ended, having a uniform shape and constant internal diameter.
Phase-Selective Synthesis of Calcium Carbonate Polymorphs
Authors: Doxsee Kenneth M. , Saulsbery Robin L. 
Published: April 2011

AbstractThrough the use of solubilizing agents, simple salt metathesis reactions may be translated from aqueous solution to the milieu of organic solvents. When applied to the crystallization of calcium carbonate through the reaction of calcium chloride with sodium bicarbonate in “complexation-mediated” crystallization leads to the selective formation of a metastable phase, vaterite, rather than to calcite, the phase obtained from aqueous solution. Impacts on the formation of the third anhydrous phase of calcium carbonate, aragonite, are also noted. These studies suggest an additional mechanism whereby Nature may control the morphology and phase of the calcium carbonate biominerals.
Spatio-Temporal Evolution Model for Competitive Ligand Binding
Authors: Condat C.A. , Delsanto P. P. , Iordache D. , Perego G. , Ruffino E. 
Published: April 2011

AbstractLigand binding is an essential step in many biological and biochemical processes, notably protein activation. In many cases, the binding rates are determined by competition: blockers competing with ligands or decoys competing with receptors. Often, the diffusivities of the various species also play a key role. The usual modelling of these processes, however, either involves well-mixed systems, for which spatial variations are neglected, or steady-state situations for which all time evolution has ceased. The model presented here can instead account for the spatial variations that originate as a consequence of inhomogeneous initial conditions and localized binding sites. It describes their evolution in time due to a combination of mechanisms of diffusion, competition and reaction. The model, which is formulated in terms of a coupled system of equations for the probability densities of the various populations, is easy to adapt to different specific conditions and is particularly well suited for numerical calculations, e.g., on a parallel computer. Since it yields concrete predictions, it can be readily used to predict the concentrations and distributions of the various species that are needed to obtain prescribed responses.
Potential Dependent Endothelial Cell Adhesion, Growth and Cytoskeletal Rearrangements
Authors: Zhou Tiean , Braunhut Susan J. , Medeiros Diane , Marx Kenneth A. 
Published: April 2011

AbstractNormal endothelial cells (ECs), lining the blood vessels, are influenced by their interaction with the underlying potentially piezoelectric extracellular matrix (ECM). That this interaction may affect the EC metabolic state and functions in vivo prompted us to study the subsequent response of cultured ECs on indium-tin oxide (ITO) glass electrodes subjected to 1 hr of constant DC surface potential ranging from -0.3 to +0.6 V (vs. Ag/AgCl). We measured, relative to controls, cellular viability, growth rate and changes in actin microfilament organization in ECs over a subsequent 6 days in culture. The growth rate of ECs was stimulated by negative potential and inhibited by positive potential. Differences could be detected as early as three days post-potential. We also observed a potential dependent cellular shape change and actin microfilament rearrangement at positive potentials within four days of treatment. ECs changed in average cell surface area and assumed a polygonal cell shape in response to treatment. Using NBD-phalloidin stain for actin and fluorescence microscopy, microfilaments were observed to re-distribute to the periphery of the cell at positive potential, indicative of cellular stress.
Model for Dynamic Shear Modulus of Semiflexible Polymer Solutions
Authors: Gittes F. , Schnurr B. , Schmidt C. F. , Olmsted P. D. , Mackintosh F. C. 
Published: April 2011

AbstractWe discuss a dynamical model for the frequency-dependent shear modulus of an entangled solution of semifexible polymers, based on longitudinal fluctuations in filaments between entanglement points or crosslinks. The goal is to explain non-Rouse, power-law scaling of the bulk shear modulus that is found via microscopic rheology of highly entangled F-actin solutions. This generalizes a previous model for the static modulus. Hydrodynamic effects, and the validity of a local drag approximation below the scale of the mesh size, are discussed. We test aspects of our model via a molecular dynamics simulation, and also present for comparison experimental results from microrheology on F-actin.
Quantum Electrodynamics Calculation of Long - Range Interaction of Biopolymers in Intracellular Dispersion Medium
Authors: Pinchuk A. O. , Vysotskii V. I. 
Published: April 2011

AbstractThe general Lifshitz theory of van der Waals interaction was used to formulate and compute energies between the nucleotides situated on the opposite ends of a broken DNA helix. Our calculation show that infrared and ultraviolet resonances in the dielectric functions of DNA and the intracellular liquid account for less then 10 percent of the forces of interaction, at a range of 5-15 angstroms, between nucleotides. Thus the fundamental contribution to the interaction is presented by the group of resonances with frequencies of X - ray range. It was shown that during the interaction between thymine - guanine, adenine - guanine and cytosine - guanine there exists a potential barrier which prevents DNA selfrepairing after a mutanous, over a distance of about 7 - 20 angstroms, at the room temperature and with reference to the viscosity factor for pure water. All the remaining pairs of nucleotides have no such barrier. In addition the barrier vanishes and DNA undergoes complete selfrepairing with the decreace in viscosity of intracellular medium.
High Resolution Two-Dimensional Detection of Ncd Motility with Optical Tweezers
Authors: Allersma M. W. , Gittes F. , deCastro M. J. , Stewart R. J. , Schmidt C. F. 
Published: April 2011

AbstractThe ATP-dependent motility of the kinesin-related non claret disjunctional (ncd) mechanoenzyme was observed in anin vitrobead motility assay using optical tweezers in combination with a new two-dimensional displacement detection method. The detection technique is based on observing the far-field interference pattern formed in the back focal plane (BFP) of the microscope condenser by the illuminating laser focus and the light scattered from the trapped dielectric bead. The ability to observe the two-dimensional motion, with high temporal and spatial resolution, and in a manner largely independent of position in the microscope field-of-view, is the particular advantage of this detection method. In the assay, a fusion protein (GST-N195) of truncated ncd and glutathione-Stransferase was adsorbed to silica beads and the axial and lateral motions of the beads along the microtubule surface were observed. The average axial velocity of the ncd coated beads was 230 ± 30 nm/s (± std. dev.). Spectral analysis of bead motion showed an increase in viscous drag near the surface. Furthermore, we also found that any elastic constraints of the moving motors are much smaller than the constraints due to binding in the presence of the non-hydrolyzable nucleotide adenylylimido-diphosphate (AMP-PNP).
Optimal Design of Stagnation-Flow MOVPE Reactors with Axisymmetric Multi-Aperture Inlets
Authors: Gupta V. , Theodoropoulos C. , Peck J. D. , Mountziaris T. J. 
Published: April 2011

ABSTRACTAn approach for optimal design of vertical stagnation flow Metalorganic Vapor Phase Epitaxy (MOVPE) reactors that minimizes parasitic pre-reactions between the film precursors is presented. The use of axisymmetric multi-aperture inlets (e.g. tube-in-tube or concentric-ring inlets) enables the separation of incompatible precursors, while preserving the axial symmetry of the reactor. A careful selection of the inlet velocity of each stream and the distance between the inlet and the susceptor (reactor height) can lead to complete mixing just above the substrate, while keeping the contact time between the precursors in the gas phase low enough to suppress pre-reactions. This idea has been used by our group for growing high quality ZnSe films on GaAs substrates from (CH3)2Zn:N(C2H5)3 and H2Se diluted in H2 in a stagnation flow MOVPE reactor with an axisymmetric split inlet. A transport model describing the MOVPE of ZnSe, for conditions at which the growth rate is limited by the precursors' arrival rate at the surface, has been developed. A parametric study was performed aiming at identifying operating conditions in industrial-scale reactors that maximize film thickness uniformity while minimizing precursor contact time. Operation atGr/Re2<100 eliminated flow recirculations in the region above the substrate. Such recirculations may lead to formation of particulates by trapping reactants. Optimal conditions correspond to equal velocities of the inlet streams, satisfying the above criterion, and to the minimum possible reactor height leading to uniform film thickness across the substrate.
Towards the Optimization of AMT Barrel Reactors for Silicon Epitaxy
Authors: Masi M. , Radaelli G. , Roda N. , Raimondi P. , Carra S. , Vaccari G. , Crippa D. 
Published: April 2011

ABSTRACTIn this work, the epitaxial silicon deposition by SiHCl3-hydrogen mixtures in a AMT 7700 barrel reactor was analyzed through a detailed model where a three dimensional flow dynamic was solved by reduction to a two dimensional geometry under cylindrical coordinates. The model was used to investigate the role of the reactor geometry and of the process parameters on the axial deposition uniformity. A comparison with industrial experimental data was also performed.
The Roles of “3d/2d” and “3d/3d” Topography Simulators in Virtual Wafer Fabs
Authors: Cale T. S. , Merchant T. P. , Borucki L. J. 
Published: April 2011

ABSTRACTAfter discussing topography simulation, we summarize two approaches used to move surfaces in topography simulators used in virtual semiconductor wafer fabs; “front tracking” and “level set”. Front tracking is presented for two dimensional (2d) surfaces, and a number of examples are shown to demonstrate the approach. The level set approach is presented for three dimensional (3d) surfaces, and examples are shown. Though either approach could be used in both 2d and 3d topography simulators, this is by and large the current usage. Transport and reaction submodels needed for physically based process simulations will continue to be developed using experiments performed on structures that are inherently 2d, combined with three dimensional 3d transport simulations; i.e., “3d/2d” simulations. Three dimensional device structures will be generated using “3d/3d” topography simulations, using robust codes. Plasma enhanced deposition of silicon dioxide from TEOS is used as an example of how 3d/2d and 3d/3d simulations are used.
Atomistic Modeling of the Ion Implantation Step Within a 2D Process Simulator
Authors: Schmidt Bruno , Posselt Matthias , Strecker Norbert , Feudel Thomas 
Published: April 2011

ABSTRACT2D calculations of as-implanted dopant profiles are performed using a new module of the process simulator DIOS which is based on the binary collision code Crystal-TRIM. Examples derived from MOS and trench technology are considered. Good lateral and depth resolution is achieved within an acceptable computing time by combining a trajectory splitting algorithm with a method for the lateral duplication of ion trajectories.
Theoretical Modeling and Improved Thermoelectric Properties in (111) and (001) Oriented PbTe/Pb1-xEuxTe MQWs
Authors: Koga T. , Cronin S. B. , Harman T. C. , Sun X. , Dresselhaus M. S. 
Published: April 2011

ABSTRACTTheoretical modeling ofZTof (111) and (001) oriented PbTe/Pb1-xEuxTe multiple-quantum-wells (MQWs) is carried out assuming parabolic energy bands and the constant relaxation time approximation. The model calculation for the (111) oriented MQWs is compared with the recently obtained experimental results for the Seebeck coefficient and the Hall carrier concentration. The thermoelectric properties for (001) oriented PbTe MQWs are expected to have even better thermoelectric properties than the (111) oriented PbTe MQWs.
3D Atomistic Simulations of Submicron Device Fabrication
Authors: Buneat Marius M. , Dunham Scott T. 
Published: April 2011

ABSTRACTWe use the Lattice Monte Carlo method to simulate the coupled motion of vacancies, interstitials and dopants during the annealing of a 50nm channel length NMOS structure. The initial defect locations are taken from Monte Carlo ion implantation simulations. The resulting defects diffuse, recombine, pair and cluster, with rates of these atomic processes calculated based on the local environment. Dopant redistribution occurs via both displacement by vacancies as well as the formation and diffusion of mobile boron and arsenic interstitials. We use these simulations to demonstrate the potential of atomistic simulations for deep submicron devices and to explore the influence of atomistic processes on macroscopic behavior.
First-Principles Study of Point-Defect Production in Si and SiC
Authors: Windl W. , Lenosky T. J. , Kress J. D. , Voter A. F. 
Published: April 2011

ABSTRACTWe have calculated the displacement-threshold energy Ed for point-defect production in Si and SiC using empirical potentials, tight-binding, and first-principles methods. We show that—depending on the knock-on direction—64-atom simulation cells can be sufficient to allow a nearly finite-size-effect-free calculation, thus making the use of first-principles methods possible. We use molecular dynamics (MD) techniques and propose the use of a sudden approximation which agrees reasonably well with the MD results for selected directions and which allows estimates of Ed without employing an MD simulation and the use of computationally more demanding first-principles methods. We compare our results for Ed with the available experimental values. Furthermore, we have examined the temperature dependence of Ed for C in SiC and found it to be negligible.