bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ion Irradiation-Induced Amorphization in the MgO-Al2O3-SiO2 System: A Cascade Quenching Model
Authors: Wang S. X. , Wang L. M. , Ewing R. C. 
Published: April 2011

AbstractThe ion beam-induced crystalline-to-amorphous transition was studied for crystalline phases in the MgO-A12O3-SiO 2 system. Samples were irradiated with 1.5 MeV Xe+ at temperatures from 15 to 1023 K, and the dose required for amorphization was determined by in situ transmission electron microscopy. Based on a cascade quenching model, we propose that irradiation-induced amorphization is closely related to glass formation. The rate of crystallization from a melt is the controlling factor in determining the susceptibility to amorphization and glass formation. From the analysis of cascade quenching evolution, we have derived a simple relation between amorphization dose and temperature. A quantitative parameter, S0, that describes the susceptibility to amorphization is derived that considers the crystalline structure, field strength, and phase transition temperature.
Thermal Neutron Irradiation of LiNbO3 Crystals Doped with Hf and Hfmg
Authors: Marques J. G. , Kling A. , Soares J. C. , Silva M. F. Da , Diétguez E. , Agullö-Löpez F. 
Published: April 2011

AbstractThe effects of irradiation with thermal neutrons on LiNbO3 single crystals doped with Hf and Hf,Mg were studied with ion beam and hyperfme interaction techniques, using Hf as a probe. In crystals where Hf occupies both Li and Nb sites, the fraction in Nb sites is strongly reduced after irradiation. The initial situation is recovered after thermal annealing at 973 K, in air.
Formation of Alkali Metal Layers at the Surface of Electron-Irradiated Alkali Halides
Authors: Paparazzo E. , Zema N. , Moretto L. 
Published: April 2011

AbstractScanning Auger microscopy (SAM) and reflected electron energy loss microscopy (REELM) have been used to study the chemical modifications induced by 10-keV electron bombardment at the surface of the alkali halides: LiF, NaF, NaCl and KI. Auger spectra show that the alkali-to-halogen surface ratio increases with irradiation time, although they provide no conclusive evidence as to the chemical nature of the damage layer. Conversely, REELM analysis clearly reveals the formation of alkali metal through the occurrence of characteristic bulk plasmon peaks and surface plasmon peaks, which can also be used to image the lateral distribution of the damage layer to nearly submicron spatial resolution. Some unexpected signals are observed, deriving from combination of surface plasmon excitations with bulk plasmon excitations, and tentatively interpreted as arising from the inhomogeneous morphology of the alkali metal layer.
Electron and X-Ray Photon Radiation Effects on Surfaces of Lead Silicate Glasses
Authors: Wang Paul W. 
Published: April 2011

AbstractRadiation effects on insulators have been extensively studied in terms of radiation induced damage. However, little work has concentrated on in situ surface modification during irradiation and the evolution of surface relaxation after the termination of irradiation. In this work, 1.3 keV electrons and 1.2536 keV Mg Kα X-ray photons were applied to investigate radiation effects on surface structural changes during irradiation and relaxation. The microstructure and composition of lead silicate glass were investigated in situ in an ultra-high-vacuum (UHV) environment by X-ray Photoelectron Spectroscopy (XPS). Similar surface radiation effects were observed using both types of radiation which included permanent metallic lead separation from the glass network resulting from Pb-O bond breaking, bimodal distribution of the 0 is XPS signal due to bridging and non-bridging oxygens, gradual increase of total lead and silicon concentrations and gradual decrease of oxygen concentration during relaxation. Different radiation effects for electron beam and X-ray photons were also observed. For photon irradiation, silicon and lead continuously accumulated while the oxygen on the surface continuously decreased during irradiation and relaxation. In the case of electron irradiation, both silicon and lead were depleted from the surface during irradiation and accumulated during relaxation. Opposite concentration changes were observed for oxygen; it increased during irradiation and decreased during relaxation. The experimental results are discussed in terms of charge effects, secondary electron yield, field-enhanced diffusion, non-bridging oxygens and nucleation of metallic lead.
Radiation Effects Of Vacuum Ultraviolet Laser Photons on Silicon Dioxide
Authors: Kurosawa K. , Herman P. R. , Kurmaev E. Z. , Shamin S. N. , Galakhov V. E. , TakigawA Y. , Sasaki W. , Yokotani A. 
Published: April 2011

AbstractThe argon excimer laser provides 9.8-eV photons that readily surmount the electronic bandgap energy of SiO2 (∼9.0 eV), directly generating excitons in a single-photon absorption process. We have shown by Si L2,3 (Si 3s→2p) X-ray emission spectroscopy, Si 2p X-ray photoelectron spectroscopy and Raman spectroscopy that this absorption process is responsible for silicon precipitation in the silica. The X-ray emission studies further show that the silicon precipitates are crystalline, forming in highest concentration in 120–230 nm layer beneath the laserirradiated surface. Silicon precipitation was not observed on samples irradiated with 146-nm krypton excimer radiation due to a smaller 8.5-eV photon energy that is below the silica bandgap.
Improvement of the Nucleation and Growth of Thin Film Phosphors for Electroluminescent Flat Panel Displays
Authors: Moss T.S. , Espinoza B.F. , Dye R.C. 
Published: April 2011

AbstractThe deposition of CaGa2S4:Ce has been accomplished using a commercial liquid delivery system on two substrate surfaces: ZnS and SrS. However, the film deposited on ZnS was not of satisfactory quality because of the formation of an amorphous layer and a high amount of residual porosity within the deposition. The use of a SrS layer on top of the ZnS improved the nucleation by reducing the interfacial energy between the substrate and deposition. It greatly reduced the porosity in the coating and reduced the formation of the amorphous layer. The crystallinity of the CaGa2S4 400 peak was also increased by a factor of ten when a layer of SrS was used. Further, the FWHM of the 400 peaks from the two depositions was not significantly different, indicating that the crystallite size and strain was approximately the same. The B40 was increased by a factor of two, from 1.84 cd/m2 for ZnS to 3.67 cd/m2 for SrS. This increase is an improvement in the performance of the films and is attributable to the increase in the crystallinity. To utilize these improvements, the ability to deposit both the SrS and CaGa2S4:Ce layers within the same reactor has been developed.
Nonlinear Optical Microscopy for Imaging Patterned Self-Assembled Monolayers
Authors: Smilowitz L. , Jia Q.X. , Yang X. , Li D.Q. , McBranch D. , Robinson J.M. 
Published: April 2011

AbstractWe have used the inherent surface sensitivity of second harmonic generation (SHG) to develop an instrument for nonlinear optical (NLO) microscopy of surfaces and interfaces. This optical technique is ideal for imaging nanometer thick self-assembled monolayers (SAM's) which have been patterned using photolithographic techniques. In this paper we demonstrate the application of SHG microscopy to patterned SAM's of the noncentrosymmetric molecule calixarene and discuss other potential applications for this new technique.
Scaling Properties of Submonolayer Growth Including Evaporation and Defects
Authors: Larralde H. , Jensen P. , Meunier M. , Pimpinelli A. 
Published: April 2011

AbstractWe present a model for thin film growth by particle deposition that takes into account the possible evaporation of the particles deposited on the surface as well as the effect of point defects. Our focus is on the early formation kinetics of two-dimensional islands on the surface, in particular in the scaling properties of the maximum number of islands formed on the surface. Most of our results are obtained through the analysis of rate equations describing the system. They are supported by simple scaling arguments and are confirmed by extensive computer simulations. We find significant differences with previous studies of this system which arise from different physical hypotheses concerning the mechanisms of island growth in the presence of evaporation.
The Effect of Si Additions on the Epitaxial Growth of Gel−x Cx Alloys on Si(100)
Authors: Yang Bi-Ke , Weil J. D. , Krishnamurthy M. 
Published: April 2011

AbstractWe report on the differences in the epitaxial growth mechanisms between Ge1−xCx (O<x<0.1) and Ge1−x−ySixCy (x=0.2, 0<y<0.05) alloys grown on Si(100) using low temperature( 200°C) molecular beam epitaxy. Thin films (50˜65nm) were characterized in situ by RHEED and ex situ by transmission electron microscopy and x-ray diffraction. With increasing C concentration, the microstructure of both Ge and GeSi alloys changes from 2D layer growth to 3D islanding. The d400 spacing of the relaxed alloys decreases marginally, with a maximum of 1at.% C being substitutionally incorporated. Ge-C films with higher C content have a high density of planar defects, typically twins and stacking faults. The addition of 20% Si does not appear to increase the amount of substitutional C in the films. Rather, the additions of 20% Si to Ge-C alloys somehow seems to enhance the tendency for the formation of planar defects.
Kinetic Model for Layer-By-Layer Homoepitaxial Growth
Authors: Trofimov V. I. , Mokerov V. G. , Shumyankov A. G. 
Published: April 2011

AbstractThe new kinetic model for homoepitaxial growth on a singular surface is presented. The model combines a familiar rate equations approach and a concept of a feeding zone that allows to connect the growth processes in neighbouring monolayers. The model involves the irreversible 2D nucleation, growth and coalescence of the islands in each growing monolayer and consists of an infinite set of coupled rate equations for the adatom and island densities and coverage in successive monolayers. With using this model the temporal evolution of the surface morphology (rms roughness and RHEED intensity) is studied. It is shown that the growth mode is fully determined by a single dimensionless parameter μ = D/J where D and J are the normalized surface diffusion coefficient and deposition flux, respectively. There exist five regions of m corresponding different growth regimes varying from smooth 2D layer-by-layer growth at sufficiently high values of μ (>108) to very rough Poisson-like random deposition growth at μ<10−4. The extension of the model to the case of heteroepitaxy is also discussed.
Vacancy Diffusion Kinetics on Si(111) and (001) Surfaces Studied by Scanning Reflection Electron Microscopy
Authors: Watanabe Heiji , Ichikawa Masakazu 
Published: April 2011

AbstractThe kinetics of vacancy diffusion on Si(111) and (001) surfaces are studied by using scanning reflection electron microscopy (SREM). Two types of layer-by-layer etching (reversal of step-flow growth and two-dimensional vacancy island nucleation) are observed during lowenergy Ar ion irradiation (500 eV) at elevated substrate temperatures. This means that vacancies created by low-energy ion impact diffuse on the surfaces, and are annihilated at the step edges. Although isotropic vacancy diffusion is observed on Si(111), anisotropic vacancy diffusion along the dimer rows and preferential vacancy annihilation at the SB steps are observed on Si(001). This anisotropic vacancy diffusion results in single-domain formation. The diffusion length of vacancies is estimated from the width of the denuded zones, which are formed on both sides of the atomic steps by thermal heating after the introduction of vacancies at room temperature. The activation energy of 3.0±0.2 eV obtained for Si(111) corresponds to the potential barrier both for surface adatom diffusion and for lateral binding energy to release adatoms from the step edges. For Si(001) surfaces, the activation energy obtained for vacancy diffusion along the dimer rows is 2.3±0.2 eV. The vacancy diffusion model mediated by dimer vacancy complexes, rather than by single-dimer vacancies, best accounts for our experimental results.
Shallow Donor Formation In Hydrogen-Implanted Silicon
Authors: Tokuda Yutaka , Iwata Hiroyuki , Ito Akira 
Published: April 2011

AbstractFormation of shallow donors has been studied in 100-keV hydrogen-implanted n-type silicon with a dose of 1×1015 cm−2. Annealing experiments are made in the temperature range 100 to 800°C. Gold Schottky contacts are fabricated on these samples to obtain carrier concentration profiles. The hydrogen profiles are measured by secondary ion mass spectroscopy. In the annealing temperature range 350 to 450°C, an increase of the carrier concentration is observed near the surface region with almost flat depth profiles. The well- known hydrogen-related donors (1st shallow donors) disappear around 400°C, while shallow donors (2nd shallow donors)observed here decrease above 500 °C. Hydrogen profiles show almost no change in the 2nd donor formation temperatures, although hydrogen starts to outdiffuse at 250°C. This indicates that the 2nd shallow donors are related to hydrogen atoms and to implantation-induced damage. The implantation-induced defects trap diffusing hydrogen atoms, which leads to the formation of the 2nd shallow donors.
Vibrational Spectroscopy Of Gold Hydrogen Complexes In Silicon
Authors: Evans M. J. , Gornstein M. G. , Stavola Michael 
Published: April 2011

AbstractSeveral vibrational bands have been observed in the region 1750–1900 cm−1 for n-type silicon into which gold and hydrogen had been introduced by high temperature diffusion. This paper focuses primarily on a defect which gives rise to bands at 1813.3 and 1827.1 cm−1. This center contains a single hydrogen atom and has two charge states in the gap with trigonal symmetry. We propose a tentative model in which this complex contains a substitutional Au atom and a single hydrogen atom at one of two possible antibonding sites, bonded either to Au or to Si. A defect observed previously in Si samples doped with Pt and H which gives rise to hydrogen stretching bands at 1880.7 and 1897.2 cm−1 has similar properties to the Au-H complex discussed here, suggesting that these defects have the same structure. Other hydrogenstretching modes observed in Si samples that contain Au and H are also discussed.
Dislocation Interactions And Their Impact On Electrical Properties Of GeSi-Based Heterostructures
Authors: Ringel S. A. , Grillot P. N. 
Published: April 2011

AbstractSubstantial improvements in the quality of relaxed, heteroepitaxial GeSi layers have occurred in the past few years due to both the development of compositionally-graded buffer layers and to an improved understanding of strain-relaxation in lattice-mismatched epitaxy, which have led to low dislocation densities within these layers. As a result, high performance GeSi devices have been achieved which has fueled yet greater device design flexibility through the use of relaxed GeSi layers over a wider range of alloy compositions and lattice constants. A complete understanding of the properties of all defects that result from strain-relaxation is essential to realize high performance and reliable devices, especially as the lattice-mismatch strain becomes more severe. While the structural properties of dislocations in relaxed GeSi layers have been studied in detail, the electronic properties of these defects and their consequences on the overall electrical properties of relaxed GeSi layers are not well understood. In this paper, we show that for high quality (low dislocation density) relaxed layers, clusters of intrinsic point defects formed by dislocation interaction, rather than the dislocations themselves, now dominate the deep level spectrum. We further show that these defects reduce the electronic material quality for films grown by UHVCVD at low temperatures (650 °C) in comparison to films grown at temperatures > 800 °C even though all films have similarly low threading dislocation densities. Using DLTS, spreading resistance, EBIC and Hall effect measurements, these defects are shown to introduce a low concentration of hole traps from Ev, + 0.05 to Ev + 0.30 eV that compensate and type convert nominally undoped GeSi layers grown at 650 °C to p-type. Annealing studies indicate that these defects anneal out at ∼ 750 – 800 °C(2w, hich is accompanied by conductivity type reversal to ntype, elimination of compensation and increased diffusion length. These observations, in addition to the precise position of each energy level, closely correlate with earlier results on plasticallydeformed bulk Si, suggesting that these defect complexes are of intrinsic origin. We conclude that strain-relaxation in graded heterostructures causes considerable dislocation interaction which introduces point defect complexes associated with dislocations that, in addition to threading dislocation density, must now be considered as an important factor for achieving high electronic quality, relaxed GeSi layers.
Growth Induced Alignment Of The First Neighbor Shell Of CAs In AlxGa1−xAs
Authors: Zheng J. -F. , Stavola Michael , Abernathy C. R. , Pearton S. J. 
Published: April 2011

AbstractWe have discovered a growth-induced alignment of the Al and Ga first neighbors of CAs, acceptors in AlxGa1−xAs grown by metalorganic molecular beam epitaxy. This growth induced alignment has been detected from the polarization dependence of the C atom's vibrational absorption bands that the alignment gives rise to. The alignment of the first neighbor shell of CAs also gives rise to aligned CAs-H complexes when the C is passivated by H. This leads to polarized H-stretching absorption bands which have also been observed. The growth-induced alignment provides information which helps us to assign the complicated CAsvib rational spectrum observed in the AlxGa1−xAs alloys.
Characterization Of APB's In GaP
Authors: Cohen Dov , Carter C. Barry 
Published: April 2011

AbstractAntiphase boundaries in GaP crystals epitactically grown on Si (001) have been characterized using transmission electron microscopy. Convergent-beam electron diffraction was used to identify the antiphase-related grains. The antiphase boundaries were observed to adopt facets parallel to specific crystallographic orientations. Furthermore, stacking-fault-like contrast was observed along the interface suggesting that the domains may be offset from one another by a rigid-body lattice translation.
Low Temperature Photoluminescence Properties Of In-Situ Zn Doped InP Layers Grown By Lp-Mocvd
Authors: Moon Y. B. , Si S. K. , Yoon E. , Kim S. J. 
Published: April 2011

AbstractIn situ Zn-doped InP layers are grown by low pressure metalorganic chemical vapor deposition at 620°C. Hole concentration increases with dopant flow rate, but reaches a saturated hole concentration of approximately 1.5 × 1018/cm3. Differently from the Zn-diffused InP case, photoluminescence (PL) of the in situ Zn doped InP shows band edge peak, e/D-A peak and distant D-A peak up to the hole concentration of 7.6 × 1017/cm3. These results can be explained by less generation of interstitial Zn atoms during in situ doping. PL characteristics of the in situ Zn-doped InP at the saturated hole concentration is extensively studied to explain its compensation mechanism. Two new deep bands, presumably responsible for the hole saturation behavior, are observed for the first time.
Defect States In p-ZnSe:N Grown By MOVPE
Authors: Fujita Shizuo , Ogata Ken-Ichi , Kawaguchi Daisuke , Peng Zhi Gang , Fujita Shigeo 
Published: April 2011

AbstractConcentration and origin of defect states in p-type nitrogen-doped ZnSe (p-ZnSe:N) grown by metalorganic vapor-phase epitaxy (MOVPE) are discussed by means of timeresolved photoluminescence and deep level transient spectroscopy. Thermal annealing, which is a useful tool for realizing p-type conductivity, results in deep defect states which seem to be associated with Zn vacancies and with nitrogen acceptors. By lowering the annealing temperature, the trap concentrations can be successfully reduced without seriously sacrificing the acceptor activation efficiency, although further reduction of Zn vacancies is pointed out as a remaining requirement for the improvement of quality of MOVPE-grown p-type layers.
Identification Of The Native Vacancy Defects In ZnSxSe1−x And MgyZn1−y SxSe1−x by Positron Annihilation
Authors: Saarinen K. , Laine T. , Skog K. , Oila J. , Hautojärvi P. , Rakennus K. , Uusimaa P. , Salokatve A. , Pessa M. 
Published: April 2011

AbstractWe show how positron annihilation can distinguish vacancies in the different sublattices of a compound semiconductor by performing experiments in ZnSxSe1−x and Mgy Zn1−ySxSe1−x layers. We identify the Se vacancies (Vse) in N-doped and the Zn vacancies (Vzn) in Cl-doped material by the shape of the core electron momentum distribution. The charge of the defect involving VSe is neutral or negative in the p-type alloys, suggesting that the Se vacancy is complexed with an acceptor. The concentration of the VSe complexes is high (≥ 1018 cm−3 ), indicating that their role is important in the electrical compensation of p-type ZnSxSe1−x and MgyZn1−y SxSe1−x.
Electrical Characterization Of Nitrogen Acceptors In p-ZnSe/p-GaAs Grown By Molecular Beam Epitaxy
Authors: Seghier D. , Gislason H.P. 
Published: April 2011

AbstractUsing current-voltage measurements, deep-level transient spectroscopy and admittance spectroscopy we investigated nitrogen doped ZnSe grown on p-GaAs substrates by molecular beam epitaxy. Three major hole traps were observed with energy levels at 0. 11, 0.46, and 0.56 eV from the valence band. We attribute the level at 0.11 eV to a nitrogen acceptor. No other direct observations of this important acceptor level in p-ZnSe have been reported in the literature so far. The two remaining levels may originate from the nitrogen doping process. In addition, reverse current-voltage characteristics of the ZnSe/GaAs heterojunction show a hysteresis at low temperature and a soft saturation. At a constant reverse bias the current increases slowly until it reaches a steady state value. This behavior is attributed to a slow voltage-induced barrier lowering due to the presence of mismatch interface states. Therefore, these analyses are of a major interest for applications of ZnSe/GaAs based devices and illustrates the necessity of improving the growth conditions of such structures.
Hrtem Characterization of 6H-15R Polytype Boundaries in Silicon Carbide Grown by Physical Vapor Transport
Authors: Sanchez E. K. , Graef M. De , Qian W. , Skowronski M. 
Published: April 2011

AbstractThe interface between 6H and 15R polytypes of silicon carbide, grown by Physical Vapor Transport, was studied by high-resolution transmission electron microscopy. The sample was investigated in cross-section cut perpendicular to the [11.0] irection. The atomic stacking sequence at the interface of the polytypes was determined. Polytype boundaries with orientations parallel and perpendicular to the 6H c-axis were investigated. Stacking faults associated with low angle grain boundaries in both 6H and 15R regions were observed and the 15R regions systematically showed a higher fault density than the 6H regions.