bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low Temperature Epitaxy Of Si/Si1-xGex/Si Multilayers By Low Pressure Rtcvd For Very Thin Soi Applications
Authors: McNeill D.W. , Gay D.L. , Lip X. , Armstrong B.M. , Gamble H.S. 
Published: April 2011

AbstractThe growth by rapid thermal chemical vapour deposition of Si/Si1-xGex/Si multilayer structures, suitable for thin bond and etch-back silicon-on-insulator fabrication has been investigated. Surface topography was studied by scanning probe microscopy, and layer contamination by secondary ion mass spectrometry. Smooth layers are only achieved at high growth temperatures (>700°C), and when surface oxide contamination is reduced by a combination of ex-situ HF vapour treatment and in-situ high temperature H2 bake. A surface peak-to-peak roughness of 15nm for a Si/Si1-xGex/Si multilayer structure has been achieved by reducing the growth time at 700°C or less. Further improvement is possible, especially if carbon contamination can be reduced.
Thermal Stability Of SiGe/Si Quantum Well Structures Grown By APCVD
Authors: Zhao Q. X. , Nur O. , Södervall U. , Patel C. J. , Willandera M. , Holtz P.O. , de Boer W.B. 
Published: April 2011

AbstractSingle and double Si1-xGexx/Si quantum well (QW) structures, which were grown by atmospheric pressure chemical vapor deposition (APCVD), are characterized by photoluminescence and secondary ion mass spectrometry. Systematic post-growth annealing treatments were carried out at temperatures between 600°C and 1100°C in pure N2 ambient. The interdiffusion between the Si layer and the Si1-xGex, well layers occurs at the annealing temperature around 900°C. The diffusion coefficient is deduced at different temperatures from SIMS measurements for single QW structures. The activation energy is about 3.9 eV in the temperature range between 950°C and 1100°C. The double QW structures show a similar value, but the accurate value is more difficult to obtain because it is more complicated to analyze the SIMS profile of the double QW structures. The intensity of the exciton recombination related to carriers confined in the double QW structures decreases with increasing annealing temperatures and becomes strongly suppressed at 750°C. When the annealing temperature is increased further, the intensity of the QW emission recovers. The results indicate that nonradiative centers were generated at annealing temperature of about 750°C
Low-Temperature Epitaxial Growth of IN-Situ HeavilY B-Doped Si1-xGex, Films Using Ultraclean LPCVD
Authors: Morrya A. , Sakuraba M. , Matsuura T. , Murota J. , Kawashima I. , Yabumoto N. 
Published: April 2011

AbstractIn-situ heavy doping of B into Si1-xGex epitaxial films on the Si(100) substrate have been investigated at 550°C in a SiH4(6.0Pa)-GeH4(0.1−6.0Pa)-B2H6(1.25 ×10−5−3.75 × 10−2Pa)-H2(17–24Pa) gas mixture by using an ultraclean hot-wall low-pressure CVD system. The deposition rate increased with increasing GeH4 partial pressure, and it decreased with increasing B2H6 partial pressure only at the higher GeH4 partial pressure. As the B2H6 partial pressure increased, the Ge fraction scarcely changed although the lattice constant of the film decreased. These characteristics can be explained by the suppression of both the SiH4 and GeH4 adsorption/reactions in a similar degree due to B2H6 adsorption on the Si-Ge and/or Ge-Ge bond sites. The B concentration in the film increased proportionally up to 1022cm3 with increasing B2H6 partial pressure.
The Formation of Abrupt N+ Doping Profiles Using Atomic Hydrogen and Sb During Si MBE
Authors: Thompson P.E. , Silvestre C. , Twigg M. , Jernigan G. , Simons D.S. 
Published: April 2011

AbstractPreviously, atomic hydrogen has been shown to be effective in reducing the segregation of Sb on Si(100) during solid source molecular beam epitaxy growth. In this work we have investigated the electrical activation of the Sb. Using Hall measurements, spreading resistance profilometry, and secondary ion mass spectrometry, we have demonstrated that the co-deposition of atomic hydrogen during Sb doping of Si at 500°C produced well-defined doping spikes. Comparing the sheet carrier concentration obtained by Hall measurements to the Sb atomic concentration obtained by SIMS, the overall activation of the Sb was greater than 50%.
Raman Spectroscopy of Epitaxial Si/Si1-xGe, xHeterostructures
Authors: Liu Ran , Zollner Stefan , Liaw Ming , O'meara David , Cave Nigel 
Published: April 2011

AbstractRaman scattering studies were carried out on epi Si/Si1-xGex (x = 0.1 to 0.3) heterostructures consisting of a thin Si cap layer (100 - 400 A˚), a grade-down Si1-xGex layer, a constant Si1-xGex, buffer layer and a grade-up graded Si1-xGex layer on (100) oriented Si substrates. Different Ge composition, Si1-xGex layer thicknesses and thermal treatment were used to achieve different relaxation in the Si1-xGex layers. It has been revealed that, to a very good approximation, the absolute strains in the cap Si and constant Si1-xGex layers follow a simple sum-rule that is imposed by the lattice mismatch between unstrained Si and completely relaxed Si1-x Gex. This sum rule can be used to determine the Ge composition and stresses in both cap Si and constant Si1-xGex layers. Excellent agreement was found between the theoretical curve obtained with LO phonon strain coefficient b=−930cm−1 and the experimental total strain for all samples, regardless of the degree of the relaxation of the grade-up Si1-xGex layer.
Impact of The ge Content on The Radiation Hardness of Hetero-Junction Diodes in Sige Strained Layers
Authors: Ohyama H. , Simoen E. , Claeys C. , Takami Y. , Hayama K. , Hakata T. , Tokuyama J. , Kobayashi K. , Sunaga H. , Poortmans J. , Caymax M. 
Published: April 2011

AbstractThe degradation of the electrical performance of strained Si1-xGex epitaxial diodes by 220-MeV carbon particles is reported and compared with the effect of 20-MeV alpha rays and 20-MeV protons. The macroscopic damage is studied in a broad fluence range and for different Ge contents, ranging from 8 to 16 %. It is shown that the radiation damage of carbon irradiated diodes is about one order of magnitude larger than that for alpha ray irradiation, which can be explained by considering the difference of the nonionizing energy loss (NIEL). It is observed that the reverse current at a fixed bias increases with increasing fluence, while the rate of increase decreases with increasing fluence and/or Ge content. The fact that a close to square root dependence exists between the boron deactivation in the diode depletion region, derived from capacitance-voltage measurements and the reverse current increase suggests that the device degradation is dominated by radiation induced deep levels associated with interstitial boron complexes.
Growth of Ain on Si(111) by Plasma-Assisted Molecular Beam Epitaxy: Application to Surface Acoustic Wave Devices
Authors: Schenk H. P. D. , Kipshidze G. D. , Weihnacht M. , Weihnach M. , Kaiser U. , Schulze J. , Richter Wo. 
Published: April 2011

AbstractEpitaxial wurtzite aluminum nitride (AIN) films have been grown on (111) oriented silicon substrates by plasma-assisted solid source molecular beam epitaxy (MBE). The growth has been performed in the two-dimensional (2D) growth mode. Occuring surface reconstructions have been monitored by reflection of high-energy electron diffraction (RHEED). The films have been characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM). 2D grown films exhibit atomically smooth surfaces, are singlecrystalline and void of oriented domains. High-resolution (HR) TEM micrographs of the heterointerface show the presence of an interfacial atomic arrangement where (5:4) unit cells coincide along the AIN[2110]/Si[110] direction.Surface acoustic wave (SAW) properties of MBE-grown AIN(0001)/Si(ll1) have been studied for the first time. The AIN film exhibits very good piezoelectricity. The SAW time response indicates low scattering of the waves during their propagation. An electromechanical coupling coefficient (EMC) of 0.07% has been measured for the present interdigital transducer (IDT) geometry.
Si/SiGe and III-V Integrated Circuit Technology for Next Generation High-Speed Systems: Comparisons and Tradeoffs
Authors: Larson Lawrence E. 
Published: April 2011

AbstractThis paper will summarize the technology tradeoffs that are involved in the implementation of high-speed integrated circuit technology for communications applications. The advantages of Si/SiGe and III-V technology with respect to CMOS and Si bipolar technologies are discussed.
Improved process window using low-carbon Gexsil-x-yCyEpitaxial layers
Authors: Mocuta A. , Greve D.W. , Strong R.M. 
Published: April 2011

AbstractProcessing of silicon-based heterojunction devices is severely constrained by the relaxation of strained epitaxial layers. Generally the equilbrium critical thickness cannot be exceeded if high-temperature process steps such as oxidation and diffusion are performed. In this paper, we report on the beneficial effects of small amounts of carbon ( 0.2%) added to germanium-silicon epitaxial layers. We will show that such low concentrations result in a substantial decrease of boron diffusivity and strain relaxation. We will also report on the fabrication of GexSil-x-yCy heterostructure MOS capacitors with a channel thickness of 300 A° and a maximum germanium fraction of 50% A thermal oxidation at 800 ‘C was performed resulting in good C(VG) characteristics along with improved hole confinement.
Heteroepitaxy of GaAs on CaF2/Si(111) By Surface Free Energy Modulation Method
Authors: Kawasaki K. , Tsutsui K. 
Published: April 2011

AbstractAn epitaxial GaAs layer was grown on a CaF2 (111) by means of surface free energy modulation of CaF2 by one-monolayer-height island formation. An additional low-temperature growth at a final stage of growth of the CaF2 layer on Si(111) produced high density islands whose height was one monolayer of CaF2. This surface structure contributed to enhance wettability of overgrown GaAs. Two-step growth sequence was also examined in order to grow GaAs layer on the modified CaF2/Si(111) with good crystallinity. The electron mobility of 2,000cm2/Vs in a Si doped GaAs layer (6×1017 cm−3) was obtained by the combination of the surface energy modulation method and the two-step growth method.
Computer Simulation of Defect Production and Behaviour in Displacement Cascades in Metals
Authors: Bacon D.J. , Gao F. , Barashev A.V. , Osetsky Yu.N. 
Published: April 2011

AbstractRecent research using molecular dynamics to simulate radiation damage due to displacement cascades in metals is reviewed. It includes results dealing with the effect on defect formation of primary knock-on atom energy and irradiation temperature. Clear dependencies and trends have emerged in these areas. In terms of the development of models to describe the evolution of radiation damage microstructure, the important parameters are not only the total number of Frenkel defects but also the distribution of their population in clusters and the form and mobility of these clusters. Results on these aspects are reviewed and it is shown that computer simulation is providing detailed information that paves the way for successful development of models of the evolution of damage beyond the stage of the cascade process.
Computation of Microsegregation and Microstructure in Solidification with Fluid Convection
Authors: Juric D. 
Published: April 2011

AbstractThe effects of fluid flow on the dendritic solidification morphology of pure materials is studied using a computational methodology based on a two-dimensional front tracking/finite difference method. A general single-field formulation is presented for the full coupling of phase change, fluid flow, and heat transport in both the solid and liquid phases. This formulation accounts for interfacial rejection/absorption of latent heat, interfacial anisotropies, discontinuities in material properties between the liquid and solid phases, shrinkage/expansion upon solidification and motion and deformation of the solid. Numerical results are presented for the dendritic solidification of pure succinonitrile in a shear flow. Comparison with solidification into a quiescent liquid indicates that fluid convection increases the overall rate of solidification while the growth rate of the leading dendrite tip is unchanged.
Atomistic Simulation of Mobile Defect Clusters in Metals
Authors: Osetsky Yu.N. , Bacon D.J. , Serra A. 
Published: April 2011

AbstractThe structure, stability and thermally-activated motion of interstitial and vacancy clusters in Fe and Cu have been studied using atomic scale computer simulation. All studied interstitial clusters and perfect interstitial loops (PILs) in Fe are mobile whereas their mobility in Cu can be suppressed at large sizes (bigger than 49-61 self-interstitials depending on the temperature) due to dissociation. A comparative study of relaxed configurations has shown that the structure of small perfect dislocation loops of vacancy and self-interstitial nature is very similar. Molecular dynamics simulation has demonstrated that small perfect vacancy loops (PVLs) in Fe consisting of more than 37 vacancies are stable over a wide temperature range and produce atomic displacements by a thermally-activated movement in the direction of the Burgers vector. The mechanism is qualitatively similar to that of SIA clusters studied earlier. Motion of vacancy loops in Cu does not occur because they transform into sessile configurations similar to stacking fault tetrahedra. These results point to the possibly important contribution of vacancy loop mobility to the difference in radiation damage between bcc and fcc metals, and between fcc metals with different stacking fault energy.
Molecular Dynamics Simulations of Crystal Growth from Melted silicon: Defect Formation Processes
Authors: Ishimaru Manabu , Motooka Teruaki 
Published: April 2011

AbstractMolecular dynamics calculations have been performed to simulate crystal growth from melted silicon (Si) and defect formation processes based on the ordinary Langevin equation employing the Tersoff interatomic potential. The findings of this investigation are as follows: (i) The [110] bonds at the solid-liquid interface induce the eclipsed configurations or hexagonal Si structures which stabilize microfacets composed of the {111} planes. (ii) Defect formation during crystal growth processes is due to misorientations at the {111} interfaces which result in an “elementary” grown-in defect structure including five- and seven-member rings. (iii) The “elementary” grown-in defect migrates in c-Si by bond-switching motions during further crystal pulling or annealing.
Modeling of Failure in Metallic Thin Films Induced by Stress and Electromigration: A Multiscale Computational Analysis
Authors: Gungor M. R. , Gray L. J. , Zhou S. J. , Maroudas D. 
Published: April 2011

AbstractA common failure mechanism in metallic thin-film interconnects is void propagation driven by electric fields and thermomechanical stresses. In this paper, a multiscale computational analysis is presented for predictive modeling of transgranular void dynamics. The modeling approach is hierarchical and involves atomistic simulations for property database development, molecular-dynamics simulations for understanding of void-tip mechanisms, and self-consistent mesoscopic simulations based on boundary-element methods and techniques for moving boundary propagation. An extremely rich void dynamical behavior is predicted, which includes faceting, facet selection, propagation of slits from the void surface, as well as formation of fine-scale crack-like features on the void surface, in agreement with recent experimental data.
Vacancy Migration Barrier Energetics and Pathways in Silica
Authors: Corrales L. R. , Ginhoven R.M. Van , Song J. , Jónsson H. 
Published: April 2011

AbstractA study of vacancy defect migration pathways and energetics in a-quartz is carried out using an empirical simulation methodology that is coupled with the nudged elastic band method. Results from this study indicate that the migration pathway for migration is between adjacent sites. We anticipate the results will guide modifications to empirical potentials for use in the study of point defect formation of more complex systems.
Primary and Secondary Grain Boundary Dislocations in Symmetric Tilt Grain Boundaries of Finite Length
Authors: Lakshmanan Annamalai , King Alexander H. 
Published: April 2011

AbstractSecondary grain boundary dislocations in large-angle grain boundaries (also called dsc-dislocations) can be described as local variations in the density of the primary (or lattice) dislocations that make up the boundary. We present a simple meso-scale simulation in which the interactions of primary dislocations with each other and with the crystal lattice produce secondary dislocations with smaller Burgers vectors and larger spacing. We use the model to explore the interactions of the primary and secondary defects with a free surface terminating the grain boundary, and demonstrate cases in which the primary dislocations dominate the interactions, forcing the secondary dislocations to increase their energy. Other cases are found, for which all of the dislocations can respond in such a way that their energy decreases. The creation of interfacial disclinations is also demonstrated.
Digital Material: A Framework for Multiscale Modeling of Defects in Solids
Authors: Myers C. R. , Arwade S.R. , Iesulauro E. , Wawrzynek P.A. , Grigoriu M. , Ingraffea A.R. , Dawson P.R. , Miller M.P. , Sethna J.P. 
Published: April 2011

AbstractWe are designing and developing a novel software environment - the Digital Material -to support materials modeling across many length and time scales, in order to develop improved descriptions of material structure and evolution. Software support is required for high-performance numerical kernels, lightweight infrastructures for prototyping, steering and analysis, information transfer across scales, coupling of disparate simulation modules, and collaboration between a multidisciplinary collection of researchers.
Modeling of Inelastic Deformation of f.c.c, Single- and Polycrystalline Materials with Low Stacking Fault Energies
Authors: Staroselsky A. , Anand L. 
Published: April 2011

AbstractA new rate-independent constitutive model for plastic deformation of crystalline materials deforming by slip and twinning has been formulated, and implemented in a finite-element program. We have simulated three different structural levels by choosing representative volume elements (RVEs) as (i) a small part of a single crystal for the analysis of the heterogeneity of plastic deformation in single crystals, (ii) a whole single crystal for polycrystal simulations, and (iii) a group of crystals for a Taylor-type model of polycrystals. We show that the predictions for the texture and stress-strain response from the model are in reasonably good agreement with experiments in plane-strain compression for a different single crystal and polycrystalline f.c.c, materials.
AB Initio Study of Changes in the Magnetism of Iron During the BCC-HCP Phase Transformation
Authors: Šob M. , Friák M. , Wang L.G. , Vitek V. 
Published: April 2011

AbstractThe pressure-induced bcc-hcp transformation in iron is studied ab initio by following a constant-volume one-parameter transformation path. The calculations are performed in the generalized gradient approximation (GGA). It is shown that the analysis of both spin-polarized and non-spin-polarized states is essential in order to correctly obtain the energetics of the phase transformation. Our calculations make it possible to locate, with high precision, the transition configuration at which the bcc ferromagnetic structure transforms into the hcp nonmagnetic structure.
Dynamics of Dissociated Dislocations in SI: A Micro-Meso Simulation Methodology
Authors: Cai W. , Bulatov V.V. , Justo J.F. , Yip S. , Argon A.S. 
Published: April 2011

AbstractThe theory of dislocation motion in materials with high Peierls stress relates dislocation mobility to the underlying kink mechanisms. While one has been able to describe certain qualitative features of dislocation behavior, important details of the atomic core mechanisms are lacking. We present a hybrid micro-meso approach to modeling the mobility of a single dislocation in Si in which the energetics of defect cores and kink mechanisms are treated by atomistic simulation, while dislocation motion under applied stress and at finite temperature is described through kinetic Monte Carlo. Three important aspects pertaining to treating the details of local structure and dynamics of kinks are incorporated in our approach: (1) Realistic complexity of (multiple) kink mechanisms in the dislocation core. (2) Full Peach-Koehler formalism for treatment of curved dislocation. (3) Detailed investigation of interaction between partials. This simulation methodology is used to calculate micron-scale dislocation mobility, with no adjustable parameters; specifically we obtain temperature and stress dependent velocity results that can be compared with experimental measurements.
Three-Dimensional Numerical Simulation of Interacting Dislocations in a Strained Epitaxial Surface Layer
Authors: Kuktat R. V. , Freundt L. B. 
Published: April 2011

AbstractIn the context of elastic dislocation theory, the glide of arbitrarily shaped dislocations near a free surface is simulated numerically. The simulation is made possible by utilizing a compact line-integral representation of the elastic field produced by a piecewise planar dislocation loop near a free surface. The interaction between a threading dislocation and a misfit dislocation in its path is simulated and the blocking effect is shown to be much more significant than found in simulations which neglect free surface effects.
Molecular Dynamics Simulation of Neutron Damage in β-SIC
Authors: Perlado J.M. , Malerba L. , Rubia T. Diaz De La 
Published: April 2011

AbstractMolecular Dynamics (MD) simulations of neutron damage in β-SiC have been performed using a modified version of the Tersoff potential. The Threshold Displacement Energy (TDE) for Si and C atoms at 300 K has been determined along directions [001], [110], [111] and [ 1 1 1 ]. The existence of recombination barriers, which allow the formation of metastable, temperature-sensitive defects even below the threshold, has been observed. Displacement cascades produced by both C- and Si-recoils of energies spanning from 0.5 keV up to, respectively, 5 keV and 8 keV have also been simulated at 300 K and 1300 K. Their analysis, together with the analysis of damage accumulation (∼3.4×10-3 DPA) at 1300 K, reveals that the two sub-lattices exhibit opposite responses to irradiation: whereas only a little damage is produced on the “ductile” Si sub-lattice, many point-defects accumulate on the much more “fragile” C sub-lattice. A preliminary study of the nature and clustering tendency of these defects is performed. The possibility of disorder-induced amorphization is considered and the preliminary result is that no amorphization takes place at the dose and temperature simulated.