bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anisotropic Lattice Relaxation and its Mechanism of ZnSe Epilayer Grown on (001) GaAs Substrate by Molecular Beam Epitaxy
Authors: Kim C.S. , Noh S.K. , Lee H.J. , Cho Y.K. , Kim Y.I. , Park H.S. , Kim T.I. 
Published: April 2011

ABSTRACTWe have investigated anisotropic lattice relaxation and its mechanism of ZnSe epitaxial layer grown on (001) GaAs substrate by MBE. Double-crystal X-ray rocking curves for (004), {115} and {404} reflections were measured as a function of the azimuthal rotation angle of the sample. We observed the sinusoidal oscillation of the FWHM of the epilayer peak for (004) reflections due to the asymmetric dislocation density along two orthogonal <110> directions, and the direction of the maximum FWHM corresponding to high dislocation density is along [110]. In addition, the strain along [110] is smaller than that along [1-10], indicating that the layer suffered anisotropic lattice relaxation. The direction of larger relaxation([l-10]) is not consistent with that of high dislocation density([110]). The results suggest that the asymmetry in dislocation density is not responsible for the anisotropic relaxation of the ZnSe epilayer.
Molecular Beam Epitaxial Growth Mode Transitions on Vicinal Surfaces
Authors: Trofimov V.I. , Medvedev B.K. , Mokerov V.G. , Shumyankov A.G. 
Published: April 2011

ABSTRACTKinetic model of MBE growth on vicinal surface is investigated. The model includes step propagation, nucleation and growth of islands on the terraces and Schwoebel barrier at descending step edges as -well. By numerical solution of kinetic rate equations for growth on stepped surface, adatom and island density profiles across a terrace are obtained. With using simple criterion for growth mode transition the "phase diagram" of growth modes in parametric space γ–β is constructed, γ∼J/D and β∼tan-2φ, where J is the atomic flux, D is the surface diffusion coefficient and φ is the substrate miscut angle. The transition curve in the γ–β plane separating step flow mode region from the mixed (step-flow+nucleation) growth mode region is well describded by a simple equation γ=A/β3 where constant A=10 and 100 with and without Schwoebel effect. The relations for critical terrace width (miscut angle) and transition temperature are derived and it is shown that these relations are in fairly well agreement with available experimental data on the MBE growth of GaAs.
Simulations of SI(100) Growth: Step Flow and Low Temperature Growth
Authors: Roland C. , Zhang Q.M. , Boguslawski P. , Bernholc J. , Gilmer G.H. 
Published: April 2011

ABSTRACTWe have investigated Si (100) homoepitaxy in variety of different temperature regimes. In the high temperature step flow regime, the growth properties of the different steps play an important role. The binding sites and diffusion barriers for a Si adatom moving over the buckled Si(100) surface and single-height steps were investigated with the ab initio Car-Parrinello scheme. The SA step edge was found to be a relatively poor sink for adatoms. By contrast, growth takes place much more rapidly at the SB step edges, so that one can understand the relatively fast growth observed at the ends of dimer rows. We have also investigated Si(100) homoepitaxy with classical molecular dynamics simulations at very low temperatures, where typically an amorphous deposit forms. By tuning the energy of the incoming atomic beams, one can lower the temperature of the amorphous to crystalline transition considerably and thereby enhance epitaxial growth.
Low Density Titanium Alloys by Non-Equilibrium Processing.
Authors: Wilkes D.M.J. , Goodwin P.S. , Ward-Close C.M. , Bagnall K. , Steeds J. 
Published: April 2011

AbstractHigh levels of Mg solid solution in Ti have been achieved by mechanical alloying in a clean atmosphere. The equilibrium solubility of magnesium in titanium is very low and processing of these alloys by conventional routes is not possible due to the high vapour pressure of Mg and alloys of Ti and Mg have only been previously achieved by vapour quenching.Contamination during milling was avoided by processing under a high purity argon atmosphere in sealed vials. Lattice parameter measurements and SEM observations suggested that complete solid solutions were achieved in alloys up to 24wt% Mg after 48h milling. For one alloy this was confirmed by high resolution TEM which showed extremely fine Ti grains in which Mg was homogeneously distributed with no clustering or precipitation.
Microhardness Enhancement in Fully Dense Fe-Based Nanophase Metallic Alloys
Authors: He L. , Ma E. 
Published: April 2011

AbstractNano-grained Fe-29Al-2Cr intermetallic and Fe-Cu two-phase composites have been consolidated to full density from powders produced by high-energy ball milling, using a sinter forging procedure developed recently in our laboratory. Grain sizes remained within nanophase range (<100 nm) after consolidation. Microhardness tests of Fe-29Al-2Cr samples consolidated to different density levels indicate a significant strengthening effect due to nanoscale grain size and a monotonic microhardness increase with decreasing residual porosity. Fully dense Fe-Cu composites exhibit enhanced microhardness as compared with rule-of-mixtures predictions, which may be attributable to interface strengthening at fcc-bcc interphase boundaries.
Defect Generation During Epitaxial Growth of CoSi2 on Miniature Sized (100) Si Substrate and its Effect on Electrical Properties
Authors: Byun Jeong Soo , Seon Jeong Min , Park Jin Won , Hwang Hyunsang , Kim- Jae Jeong 
Published: April 2011

AbstractSelf-aligned silicide (salicide) formation of epitaxial CoSi2, using a Co/Ti bilayer, on linear oxide (SiO2) patterned (100)Si substrate has been investigated. Rapid thermal annealing (RTA) at 550°C resulted in the lateral encroachment of silicide in the Si under the edge of the oxide. After RTA at 900°C, even though an epitaxial CoSi2 layer was formed on the Si substrate, defects such as lateral encroachment and voids were generated under the edge of the oxide. It was found that such defects lead to device failure due to the deterioration of the gate oxide and the shallow junction.
Hall Effect Investigation of Doped and Undoped ßB-FESI2
Authors: Brehme S. , Ivanenko L. , Tomm Y. , Reinsperger G.-U. , Staulß P. , Lange H. 
Published: April 2011

AbstractPolycrystalline ß-FeSi2 layers prepared by codeposition of Si and Fe on cold and hot Si substrates and ß-FeSi2, crystals grown by chemical vapor transport were investigated. Resistivity and Hall effect measurements revealed the p-type conductivity of undoped material and the influence of some dopants of the iron group. The activation energy of a Cr-related acceptor was determined to about 85 meV. The mobility data were found to depend significantly on the purity of the preparation process.
Morphologies and Growth Modes of Fesi and β-Fesi2 Layers Prepared by Rapid Thermal Annealing
Authors: Amesz P. H. , Jørgensen L. V. , Libezny M. , Poortmans J. , Nijs J. , van Veen A. , Schut H. , de Hosson J. Th. M. 
Published: April 2011

AbstractThis paper reports on the formation of FeSi and β-FeSi2by rapid thermal anneal (RTA). Sputtered Fe layers with a thickness of 25 nm and 40 nm on (100) Si wafers were subjected to RTA-treatment at temperatures ranging between 500 and 700 °C. This leads to three different types of growth. Two types of lateral growth and a hillock like growth. All the growth modes were nucleation controlled. The lateral growth rates of β-FeSi2 were measured at temperatures ranging from 625 to 700 °C, this provided a value for the activation energy of this process of about 1.35 eV. Positron annihilation analysis and scanning electron microscopy were used to study the onset of the transformation.It is suggested that the lateral growth appears when the Fe layer is completely transformed to FeSi before FeSi2 nucleates and that the hillock-like growth emerges when FeSi2 nucleates before the complete transformation of the Fe layer to FeSi.The RTA formed P3-FeSi2 layers have a roughness of the order of the thickness of the layer and a high defect density as observed by cross-section transmission electron microscopy. In order to decrease the surface roughening a-Si and Si3N4 capping layers were deposited with plasma enhanced vapour deposition before RTA.
Diffusion Processes in Silicides: A Comparison Between Bulk and Thin Film Phase Formation.
Authors: Gas Patrick , D'Heurle Francois 
Published: April 2011

AbstractDiffusion processes in silicide thin films play a key role both during their formation by reactive diffusion or during their use. However our unique source of information was provided by indirect analysis: growth of thin films and dopant redistribution which are quite difficult to analyse in terms of diffusion mechanisms. Recent tracer experiments conducted in bulk silicides are presented. They allow a determination of both volume (v) and grain boundary (gb) diffusion coefficients. Contrary to what is observed in certain intermetallic compounds no fast volume diffusion mechanism was found. The main difference with the behaviour of pure metals is a slightly higher value of the ratio Qgb/Qv which makes gb diffusion an efficient process in a wider temperature range.A quantitative analysis of diffusion processes during silicide formation is then possible. As an example we propose a comparison between the kinetics of growth of thin films and bulk diffusion couples in the Co/Si and Ti/Si systems. Providing that attention is paid to: i) the laws of growth which are slightly different for a phase growing simultaneously with others (bulk) and one phase growing alone (thin films), and ii) the grain size of the growing phase which is strongly dependant on temperature and thicknesses excellent agreement is obtained between the two sets of measurements. Moreover the growth rates may be calculated quite accurately from the values of the volume and gb tracer diffusion coefficients. This stresses and quantifies the role of interfacial diffusion in thin films behaviour.
Ion Beam Processed Ir/SiGe Structures
Authors: Curello G. , Gwilllam R. , Harry M. , Sealy B. J. , Rodriguez T. , Clement M. 
Published: April 2011

AbstractThe thermal reaction of Ir/SiGe structures following ion implantation induced Ir grain boundary mixing has been studied. The morphology of the final interface has been investigated by Cross-sectional Transmission Electron Microscopy (XTEM) and Rutherford Backscattering Spectrometry (RBS) has been used to detect the redistribution of constituent atoms in the reacted layers. A 20 nm iridium film was deposited in vacuum by electron beam evaporation onto p-Si1-xGex (x = 0.25, 0.33) fully relaxed MBE grown layers. Implantation conditions used were effective in amorphizing the interface-close region of the Ir film and the SiGe substrate. After regrowth, XTEM results show that the interface quality is improved with respect to the material that had not been implanted. RBS results on the other hand show Ge incorporation in the reacted layer to occur in contrast to the non implated case where the Ge piles up at the silicide/SiGe interface. The effect of a second anneal step at higher temperatures (in the range 800°C – 900°C) is also investigated.
Silicide Metallization of Aluminum Nitride Substrates for High-Temperature Microelectronics
Authors: Savrun E. , Sarikaya M. , Luan A. , Pearsall T. 
Published: April 2011

AbstractA novel metallization for aluminum nitride substrates to package silicon carbide integrated circuits for use at temperatures up to 600°C was investigated. Chemical equilibrium calculations were used to determine the chemical compatibility of several refractory and transition metal disilicides with AIN. Tungsten disilicide, niobium disilicide, and titanium disilicide were selected for thin film deposition studies. WSi2, NbSi2, and TiSi2 thin films were deposited by RF sputtering on AIN substrates and heat treated at 900°C, 1000°C, and 1200°C in an argon atmosphere. Sheet resistivities were measured and interface stabilities and structures were characterized by scanning and transmission electron microscopy imaging, electron diffraction, and energy dispersive x-ray microanalysis spectroscopy. The results show that metal silicides appear to be promising as metallization for aluminum nitride for use at temperatures above 600°C.
Temperature Dependence and Annealing Behaviour of Hf Implanted (100)Si: HfSi 2 Synthesis
Authors: Silva M. R. Da , Melo A. A. , Soares J. C. , Silva M. F. Da , Moons R. , Langouche G. , Vantomme A. , Conde O. , Lu Y.-C. , Kung H. 
Published: April 2011

AbstractWe investigated the formation of a buried HfSi2 layer by high fluence ion implantation of isotopically mass separated 179–180 Hf+ on heated silicon (100) substrates. It is shown that for the substrate temperature of 600°C a buried HfSi 2 layer is formed. By subsequent annealing at 1000 °C a continuous 12 nm HfSi2 layer on the Si surface is formed followed by 130 nm big almost spherodized HfSi2 ellipsoid and 80 nm small HfSi2 and Si grains. The annealing of samples implanted at lower temperatures show that HfSi2 is also formed but with reduced yield. A summary of the relevant data is presented.
High Resolution Electron Microscopy of Sputter-Deposited Zirconia-Alumina Nanolaminates
Authors: Schofield M. A. , Whig R. , Aita C. R. , Gajdardziska-Josifovska M. 
Published: April 2011

AbstractHigh resolution electron microscopy is employed to study the crystallography and morphology of zirconia nanocrystallites in zirconia-alumina nanolaminates and zirconia films. Unity volume fraction of tetragonal zirconia formed when the zirconia layer thickness was less than 6.2 nm, a theoretically predicted critical size for tetragonal-to-monoclinic zirconia (t -> m-ZrO2) transformation. In thicker layers, monoclinic zirconia formed, accompanied by renucleation and void formation which caused roughness to the zirconia nanolayers. The average position of the voids in the layers was 6.3 nm from the growth interface, coinciding with the critical dimension for t -> m-ZrO2 transformation.
Polysilicon Waveguides for Silicon Photonics
Authors: Agarwal Anuradha M. , Black Marcie R. , Foresi James S. , Liao Ling , Liu Yaping , Kimerling L. C. 
Published: April 2011

AbstractPhotonic integrated circuits in silicon require waveguiding through a material compatible with silicon VLSI technology. Polysilicon (polySi), with a high index of refraction compared to SiO2 and air, is an ideal candidate for use in silicon optical interconnect technology. Inspite of its advantages, the biggest hurdle to this technology is that losses of 350dB/cm have been measured in as-deposited polySi waveguide structures, as against ldB/cm losses measured in waveguides fabricated in crystalline silicon. We report methods for reducing scattering and absorption, which are the main sources of losses in this system. To reduce surface scattering losses we fabricate waveguides in smooth recrystallized amorphous silicon and Chemo-Mechanically Polished (CMP) polySi, both of which reduce losses by about 40dB/cm to 15dB/cm. Atomic Force Microscopy (AFM) and spectrophotometry studies are used to monitor surface roughness which has been reduced from an RMS roughness value of 19–20nm down to about 4–6nm. Bulk absorption/scattering losses can depend on size, structure, and quality of grains and grain boundaries which we investigate by means of Transmission Electron Microscopy (TEM). Although the lowest temperature deposition has twice as large a grain size as the highest temperature deposition, the losses appear to not be greatly dependent on grain size in the 0.1pm to 0.4pm range. Additionally, absorption/scattering at dangling bonds is investigated before and after a low temperature Electron-Cyclotron Resonance (ECR) hydrogenation step. After hydrogenation, we obtain the lowest reported polySi loss values at λ = 1.54μm of about 15dB/cm.
Fabrication of Polycrystalline Silicon on Glass from Fluorinated Precursors with the Aid of Atomic Hydrogen
Authors: Akasaka T. , He D. , Shimizu I. 
Published: April 2011

AbstractHigh quality polycrystalline silicon was made on glass from fluorinated precursors by two step growth, i.e., (1) formation of seed crystals on glass by layer-by-layer(LL) technique and (2) grain-growth on the seeds. In LL technique, deposition of ultra-thin films and treatment with atomic hydrogen was repeated alternately. Columnar grains with 200 nm dia were grown epitaxy-like on the seeds by optimizing the deposition parameters under in situ observation with spectroscopic ellipsometry.
Engineering Desired Grain Orientation and Boundaries Separating Adjacent Grains in Polycrystalline Thin Films
Authors: Rauf I. A. , Sayer M. 
Published: April 2011

AbstractA simple process, involving a controlled temperature gradient on the surface of the substrate during the deposition of a thin film is described. This technique is similar to zone-refining but produces chains of impurity free grains. Simultaneously, dopants and other defects are confined to the grain boundaries separating two such chains. For a small temperature gradient only preferred orientation is obtained within a chain. For medium values of temperature gradient the grain boundaries within a chain are engineered to be either on a low energy coincidence site lattice (CSL) or a twin depending on the magnitude of gradient. For high magnitudes of temperature gradient, the chain is predicted to be a single crystal strip.
Size Effects in BaTiO3 Thin Films
Authors: Lu X. M. , Zhu J. S. , Li P. , Jiang W. , Liu X. , Wang Y. N. 
Published: April 2011

AbstractThe size effects were studied by the measurement of optical transmittance, Raman spectra and mechanical dissipation in BaTiO3 films. The variation of energy gap, Raman peaks, Curie temperature with film thickness and grain size was observed and the possible origin was analyzed.
Annealing Characteristics of Al-Light-Rare-Earth Alloy Thin Films for Microelectronic Conductor Lines
Authors: Takayama Shinji , Tsutsui Naganori 
Published: April 2011

AbstractThe addition of La and Pr to Al thin films markedly decreases the grain size of the Al matrix and largely suppresses growth of thermal defects of hillocks and whiskers at high temperatures (350°C – 450°C). A large number of fine metallic compounds of Al11RE3 and/or Al3RE (RE = La and Pr) were segregated in an Al matrix, mostly at grain boundaries, after annealing at 350°C. The resistivities of the films after annealing at the above temperatures show very low values of less than 6 μωcm, without the salient formation of hillocks or whiskers on the film surfaces.
Variational Monte Carlo on a Parallel Architecture: An Application to Graphite
Authors: Menchi M. , Bosin A. , Fahy S. 
Published: April 2011

AbstractWe present the parallelization strategy adopted to perform Variational Quantum Monte Carlo calculations on solids on distributed-memory architectures and the issues involved in the development of the parallel programs. Results obtained by the calculation of total electronic energy of graphite using nonlocal pseudopotentials in conjunction with the Variational Monte Carlo approach will be shown.
Dynamics and Morphology of Cracks in Silicon Nitride Films: A Molecular Dynamics Study on Parallel Computers
Authors: Nakano Aiichiro , Kalia Rajiv K. , Vashishta Priya 
Published: April 2011

AbstractMultiresolution molecular dynamics approach on parallel computers has been used to investigate fracture in ceramic materials. In microporous silica, critical behavior at fracture is analyzed in terms of pore percolation and kinetic roughening of fracture surfaces. Crack propagation in amorphous silicon nitride films is investigated, and a correlation between the speed of crack propagation and the morphology of fracture surfaces is observed. In crystalline silicon nitride films, temperature-assisted void formation in front of a crack tip slows down crack propagation.
Environment Sensitive Embedding Energies of Impurities, and Grain Boundary Stability in Tantalum
Authors: Krasko Genrich L. 
Published: April 2011

AbstractMetalloid impurities have a very low solubility in Tantalum, and therefore prefer to segregate at the grain boundaries (GBs). In order to analyze the energetics of the impurities on the Tantalum GB, the LMTO calculations were performed on a simple 8-atom supercell emulating a typical (capped trigonal prism) GB environment. The so-called “environment-sensitive embedding energies” were calculated for Hydrogen, Boron, Carbon, Nitrogen, Oxygen, Phosphorus, and Sulphur, as a function of the electron charge density due to the host atoms at the impurity site. The calculations showed that, at the electron density typical of a GB, Carbon has the lowest energy (followed by Nitrogen and Boron) and thus would compete with the other impurities for the site on the GB, tending to displace them from the GB. The above energies were then used in a modified Finnis-Sinclair embedded atom approach for calculating the cohesive energies and the equilibrium interplanar distances in the vicinity of a (111) Σ3tilt GB plane, both for the clean GB and that with an impurity. These distances were found to oscillate, returning to the value corresponding to the equilibrium spacing between (111) planes in bulk BCC Tantalum by the 10th-12th plane off the GB. Carbon, Nitrogen and Boron somewhat dampen the deformation wave (making the oscillations less than in the clean GB), while Oxygen, Phosphorus and Sulphur result in an increase of the oscillations. The cohesive energies follow the same trend, the GB with Carbon being the most stable. Thus, Carbon, Nitrogen and Boron may be thought of as being cohesion enhancers, while Oxygen, Phosphorus and Sulphur result in decohesion effects.
Melting of Aromatic Compounds: Molecular Dynamics Simulations
Authors: Kung P. W.-C. , Books J. T. , Freeman C. M. , Levine S. M. , Vessali B. , Newsam J. M. , Klein M. L. 
Published: April 2011

AbstractWe have used constant pressure molecular dynamics calculations to explore the behavior at various temperatures of two molecular crystals: benzene and a brominated phenyl compound. We observed a melting transition by heating the crystals from a low temperature. In the case of benzene, we performed one heating run of about 1 ns and obtained agreement with the experimental melting point to within some 8%. We have also simulated the melting of a more complex molecular crystal that contains bromine and phenyl groups. We performed four heating runs, with different rates of heating. For total simulation times of about 100, 220, 770, and 1 I50ps, the heating runs predicted melting temperatures that differed from the experimental melting temperature by 53%, 33%, 25%, and 9% respectively.
Growth Mechanism of Si Dimer Rows on Si(001)
Authors: Yamasaki T. , Uda T. , Terakura K. 
Published: April 2011

AbstractInitial processes of Si dimer row growth on Si(001) surface is studied by the first principles molecular dynamics method. We optimize several different ad-Si clusters composed of one to four atoms on the surface and estimate activation energies for some important growth processes. At lower temperatures, a metastable ad-Si dimer in the trough between substrate dimer rows attracts monomers and tends to grow into a short diluted-dimer row in the perpendicular direction to the substrate dimer rows. In high temperatures as ad-Si dimers can diffuse, a direct dimer condensation process is possible to elongate the dense-dimer rows also in the perpendicular direction.
DFT Study of the Monocyclic and Bicyclic Ring Geometries of C20
Authors: Wang Zhiqiang , Day Paul , Pachter Ruth 
Published: April 2011

AbstractThe monocyclic and bicyclic ring geometries of C20 are optimized using both the local density functional approximation (LDA) and gradient-corrected density functional theory (BLYP). The energy of the bicyclic ring is found to be higher than that of the monocyclic ring in both LDA and BLYP calculations. The BLYP results confirm the previous single point calculation based on Hartree-Fock geometries[1], which is in favor of the monocyclic ring geometry, while the LDA results still favor the cage geometry. LDA frequencies of both ring geometries are also presented.