bluuebunny/crossref_metadata_2025_split huggingface dataset:
Iridium Silicides Formation on High Doses Ge+ Implanted Si Layers
Authors: Curello G. , Gwilliam R. , Harry M. , Wilson R. J. , Sealy B. J. , Rodriguez T. , Jimenez-Leube J. 
Published: April 2011

AbstractIn this work iridium silicidation of high dose Ge+ implanted Si layers has been studied. Compositional graded SiGe layers with a Ge peak concentration between 6 at.% and 12 at.% have been fabricated using 200 keV Ge+ ion implantation into (100) Si. A 20 nm thick Ir film was then deposited by e-beam evaporation with thermal reaction being performed to both regrow the implantation damage and form the silicide. The crystal quality of the SiGe layer and its interaction with the Ir film have been studied by cross-sectional Transmission Electron Microscopy (XTEM) and Rutherford Backscattering Spectrometry (RBS).Solid Phase Epitaxial Growth (SPEG) in the low dose case has produced a defect free SiGe layer with the formation of the IrSi phase. The annealing ambient was found to be critical for the silicidation. For the high dose case, as expected, strain relaxation related defects were observed to nucleate at a depth close to the projected range of the Ge+ implant and to extend up to the surface. A second rapid thermal annealing at higher temperatures, performed in forming gas, consumed most of the defective layer moving the silicide interface closer to the peak of the Ge distribution. A second low dose Ge+ implant following the metal deposition has been found to have a beneficial effect on the quality of the final interface. An amorphizing 500 keV Si+ implant followed by SPEG has finally been used to move the end of range defects far from the interface.
Fabrication of Epitaxial Silicides thin films by Combining Low-Energy Ion Beam Deposition and Silicon Molecular Beam Epitaxy
Authors: Shibatal H. , Makital Y. , Katsumata H. , Kimura S. , Kobayashil N. , Hasegawa M. , Hishita S. , Beye A. C. , Takahashi H. , Tanabe J. , Uekusa S. 
Published: April 2011

AbstractWe have developed successfully the combined ion beam and molecular beam epitaxy (CIBMBE) system with a newly designed Knudsen cell for Si effusion. The CIBMBE system was applied to the epitaxial growth of Sil., Cx alloy thin films on Si using low-energy ( 100 – 300 eV ) C+ ion beam. Preliminary results on the characterization of the deposited films suggest high potential and reliability of the new Knudsen cell for Si effusion, as well as high ability of the CIBMBE method to produce thermally non-equilibrium materials. In addition, they indicate that the value of x decreases with increasing IC, which suggests that the selective sputtering for deposited C atoms by incident C+ ion beams takes place during CIBMBE processing. Precipitates of β-SiC were also found to be formed in the deposited films, whose amount was observed to increase with increasing IC.
Structure and Electrical Properties of Cu/Ge Ohmic Contacts
Authors: Oktyabrsky S. , Aboelfotoh M. O. , Narayan J. 
Published: April 2011

AbstractChemistry, crystal structure, interfacial microstructure and electrical characteristics of novel Cu-Ge alloyed ohmic contacts to n-type GaAs with a very low specific contact resistivity ((4–6)×10−7 Ω·cm2 for n∼1×1017 cm−3) were investigated by various methods. The Cu-Ge alloys with a wide range of Ge concentration, from 15 to 40 at %, were prepared by depositing sequentially Cu and Ge layers (or vise versa) onto GaAs substrates at room temperature followed by annealing at 400°C. It is shown that Cu reacts only with Ge to form the ξ and ε1-Cu3Ge phases. The latter has an orthorhombic structure with average lattice parameters: a = 5.301 Å, bo = 4.204 Å, co = 4.555 Å, arising from the parent hexagonal ξ-phase by Cu-Ge ordering along ao. The interface with GaAs is atomically sharp and free from secondary phases. The ε1-Cu3Ge ordered phase which is chemically inert with respect to GaAs, is believed to be responsible for high thermal stability (up to 450°C), interface sharpness, high contact layer uniformity and low specific resistivity of 6 μΩ cm. Formation of the Cu-Ge phases creates a highly doped n+-GaAs surface layer which leads to the low contact resistivity.
First Stages of the Platinum Electroless Deposition on Silicon (100) from Hf Solutions.
Authors: Gorostiza P. , Servat J. , Morante J. R. , Sanz F. 
Published: April 2011

AbstractElectroless metal deposition based upon the addition of fluoride anions to the metal salt aqueous solution have been developed recently on the assumption that the cleanness of the substrate will be guaranteed and the deposit will be of high purity. In this work, platinum is deposited on silicon (100) from fluorinated solution at two different pH's. The influence of pH is analyzed using Tapping Mode Atomic Force Microscopy (TMAFM) to characterize the main morphological properties of the deposit. Combined TMAFM and Transmission Electron Microscopy (TEM) images are presented and X-ray Photoelectron Spectroscopy (XPS) allows us to identify the chemical nature of the silicon surface.
Preparation of WSi2 by RTA Annealing of CVD-W thin Films
Authors: Gesheva K. A. , Stoyanov G. I. , Gogova D. S. , Beshkov G. D. 
Published: April 2011

AbstractWsi2 films were prepared by rapid thermal annealing (RTA) in the temperature range of 800 -1400 °C for time durations of 15 sec -3 minutes. In some of the treatment experiments different gases were involved and a conclusion is made about the role of hydrogen favoring Wsi crystal phase growing at 800 °C. W films with thichnesses in the range 200 Å - 1000 Å were deposited on monocrystalline Si by pyrolitical decomposition of W(CO)6 in CVD reactor at atmospheric pressure and argon atmosphere. Reflection High Energy Electron Diffraction (RHEED) and Scanning Electron Microscopy (SEM) technics were used for structural characterization and FPP-100 device for resistance measurements. Results show that by solid state reaction applied at different RTA processes WSi2 phase could be formed.Resistivities as low as 2-3 mΩ.cm are obtained for 800 -1000 °C.
Steady-State Creep of Thick and Thin-Film Multilayers
Authors: Shen Y.-L. , Suresh S. 
Published: April 2011

AbstractThe steady-state creep response of multilayered polycrystalline materials subjected to cyclic variations in temperature is analyzed. The approach presented here is capable of predicting the evolution of curvature, the thermal stresses, and the dominant deformation mechanisms at any through-thickness location of each layer for prescribed layer geometries and thermo-mechanical properties of the constituent layers. The Al-Al2O3 model system is considered, where the dominant relaxation mechanism in Al is studied as the layer thickness is systematically varied. Creep due to grain boundary diffusion is found to become more significant in thin layers with a three-dimensional equiaxed grain structure. The effects of columnar grain structure in Al thin films on the thermal cycling response are also discussed.
Effect of the Grain Growth Process on the Characteristics for the Excimer Laser Crystallized Poly-Si Thin Film Transistors
Authors: Okumura Hiroshi , Tanabe Hiroshi , Okumura Fujio 
Published: April 2011

AbstractWe have found, for excimer laser crystallized poly-Si thin films, that there are two different grain growth processes that depend on the energy density. Columnar grains grow laterally at lower energy densities. The other grain growth process at higher energy densities is shown to be secondary grain growth caused by a less oriented structure with fine granular grains. A TFT with the maximum mobility is obtained at the border for the lower energy grain growth. Grain boundary and intragrain defects around grain boundary formed through the secondary grain growth reduce the mobility in spite of considerable grain enlargement.
Surface Morphology of P-Doped LPCVD Silicon Films
Authors: Plugaru Rodica , Vasile E. , Cosmin P. , Cosmin Silvia , Cobianu C. , Dascalu D. 
Published: April 2011

AbstractThe formation of silicon hillocks at the surface of amorphous and polycrystalline LPCVD silicon films, as a function of phosphorus doping was investigated by SEM, TEM replica and X-ray diffraction techniques. The phosphorus doping was performed in the concentration range from 9 × 1019cm-3 tol.5 × 1020cm-3. It was observed that the hillocks size increases with the dopant concentration for the as-doped and for annealed films. The experimental data were analysed in a model involving diffusion of silicon during the doping and recrystallization processes.
Effective Conductivity Modelling of Polycrystalline ZnO Thin Films
Authors: Robles M. , Tagüeña-Martínez J. , Río J. A. Del 
Published: April 2011

AbstractChemically deposited thin films have multiple applications, in particular for low cost solar cells production. However, due to their inhomogeneous structure, it is very difficult to predict their physical properties. In this work we present a mean field approximation to model the effective electrical conductivity of the polycrystalline ZnO chemical deposited thin films. Our model considers elliptical inclusions randomly distributed in a matrix. We compare with the experimental results of two different deposition methods: spray pyrolysis [1] and successive ion layer adsorption and reaction (SILAR) [2]. Supported by the structural information of these samples, we select the elliptical geometrical parameters. We obtain a good fit of the experimental measurements with our calculation.
Piezoresistance Gauge Factors in Heavily Boron-Doped Polysilicon from Infrared Piezoreflectance
Authors: Cali J. , Bustarret E. , Kleimann P. , Berre M. Le , Barbier D. 
Published: April 2011

AbstractHeavily boron-doped (4×1019 < [B] >1021 cm-3) polycrystalline silicon thin films on oxidized silicon cantilevers were studied by FTIR spectroscopy. The experimental reflectance spectra (400–7000 cm-l) were compared to those expected for a poly-Si/SiO2/c-Si/SiO2 multilayer where the doped layer is described by a simple Drude model. The resulting free carrier concentration and conductivity were checked against electrical measurements.The optical response of the polycrystalline layer in the medium infrared range (400–3000 cmn−1) was shown to be affected by a static uniaxial stress applied along the film plane by a four point bending mechanical device. The resulting microscopic piezoresistivity longitudinal gauge factors in the 15 - 25 range are in close agreement with those deduced from conventional electrical piezoresistivity measurements on sub-millimeter size patterns. The effective range of applicability of this contactless method and the potential application of such layers to temperature-independent miniature pressure sensors are discussed
Blanket and Local Crystallographic Texture Determination in Layered Al Metallization
Authors: Rodbell K. P. , Hurd J. L. , DeHaven P. W. 
Published: April 2011

AbstractThe effect of microstructure, including average grain size, grain size distribution, precipitate distribution and crystallographic texture, on the reliability of Al and Al-alloys is well documented. In this paper, the various x-ray methods available for measuring preferred orientation in blanket films are compared and contrasted in an effort to find the fastest, most accurate method to acquire crystallographic texture information. I(111)/I(200)ratios from Bragg-Brentano scans (θ/2θ), rocking curves, and complete pole figures (fiber plots) were compared for four Ti/AlCu films having greatly different crystallographic texture components. The results show that it matters how texture is measured in a thin film; only pole figures (fiber plots) are unambiguous. In addition, the local texture in a series of stress-voided 0.48 um wide Ti/AICuSi/TiN lines was measured using Backscattered Kikuchi Diffraction (BKD). Samples were chosen from two sets of identically prepared wafers (processed at different times) showing large differences in stress-voiding driven resistance versus time behavior. The more strongly textured (111 ) films had decreased stress-voiding lifetimes and tended to have smaller average grain sizes with slightly larger grain size distributions. This is in apparent contradiction with previous results in Al films, where improved stress-voiding and electromigration behavior were found in those films with the strongest (111 ) texture.
Direct Observation of the Effects of Cu Distribution on Electromigration Phenomena in Submicron Al Interconnects
Authors: Theiss Silva K. , Prybyla J. A. 
Published: April 2011

AbstractWe have performed time-resolved studies of the electromigration (EM) – induced formation, growth, migration, and spatial distribution of Al2Cu precipitates in submicron Al(0.5 wt. % Cu) runners. Of particular interest is the formation of the precipitates in relationship to the local microstructure of the runners, and the formation of voids and hillocks with respect to the location of the Al2Cu precipitates. Runners of widths 0.3, 0.5, 0.8, and 1.0 ýtm were tested at a current density of 2×106 A/cm2 and temperatures between 200 and 300°C. The evolution of the microstructure of the runners was evaluated using plan-view TEM, SEM, and EDX. The formation of voids and hillocks, and the growth of precipitates proceeds more rapidly as the width of the runners increases. However, a far greater number of precipitates nucleate in the 0.3 μm-wide line than in any of the others. As expected, voids are most likely to form near the cathode and hillocks near the anode. Large Al2Cu precipitates form near the anode long before failure occurs. Interestingly, the cathode-side bonding pad is not observed to serve as a good reservoir of Cu for the runners. Although the formation of voids near the cathode seems to be associated with the depletion of Cu in this region, hillocks and voids elsewhere are more likely to form at precipitates than in other parts of the line. Thus Al2Cu precipitates can act as sites for preferential EM-damage, reducing interconnect reliability.
ACRES: Adaptive Coordinate Real-Space Electronic Structure
Authors: Modine N. A. , Zumbach Gil , Kaxiras Efthimios 
Published: April 2011

AbstractA real space approach to electronic structure calculations has several important advantages. A regular real-space mesh produces a sparse, local, and highly structured Hamiltonian, which enables effective use of iterative numerical methods and parallel computer architectures. However, a regular real space mesh has equal resolution everywhere, while actual physical systems are inhomogeneous. To remedy this inherent inefficiency without losing the advantages of a regular mesh, we carry out computations on a regular mesh in curvilinear space. There are several choices involved in the implementation of the method. These include the choice of the coordinate transform, the form of the discretized Laplacian, the regularization of the ionic potential for all-electron calculations, and the method of calculating the forces. Of particular interest is the use of error analysis to optimize the grid for a given physical system. The adaptive grid is versatile enough to describe accurately a very wide class of systems, including ones with highly inhomogeneous electronic distributions. We report all-electron calculations for atoms and molecules with is and 2p valence electrons, and pseudopotential calculations for molecules and solids.
The Massively Parallel O[N] LSMS-Method: Alloy Energies and Non-Collinear Magnetism
Authors: Stocks G. M. , Wang Yang , Nicholson D. M. C. , Shelton W. A. , Temmerman W. M. , Szotek Z. , Harmon B. N. , Antropov V. P. 
Published: April 2011

AbstractWe present an overview of the locally self-consistent multiple scattering (LSMS) method. The method is based on real space multiple scattering theory, is naturally highly parallel, and has been implemented on Intel Paragon parallel platforms within the Center for Computational Sciences at Oak Ridge National Laboratory. O(N)-scaling is demonstrated for unit cells as large as 1000-atoms. We discuss in detail how the real space convergence properties of the method can be controlled by taking advantage of the stationary properties of a finite temperature Harris-Foulkes free energy functional. We show how the LSMS method can be combined with spin-dynamics to treat non-collinear magnetic states of materials. We show some preliminary results for the ground state magnetic structure of FCC Fe0.6 5Ni 0.35 alloys that indicate the possible existence of non-collinear arranges of magnetic moments in this system.
Ab Initio and Model Calculations on Different Phases of Zirconia
Authors: Schönberger Uwe , Wilson Mark , Finnis Michael W. 
Published: April 2011

AbstractIn order to get a better understanding of the energetics of ZrO2 (zirconia) ab initio calculations with the full potential linear muffin tin orbital method ( fp LMTO) have been performed on the tetragonal structure over a range of c/a and sublattice displacement. A new semi-empirical shell model is developed which makes use of Hartree-Fock calculations and includes compressible anions and quadrupolar distortions. The empirical model predicts energies for tetragonal distortion in agreement with the fp LMTO calculations. Furthermore, it enables us to understand why the seven-fold coordinated monoclinic phase is the low temperature equilibrium structure.
Distribution of Rings and Intermediate Range Correlations in Silica Glass Under Pressure-A Molecular Dynamics Study
Authors: Rino José Pedro , Gutiérrez Gonzalo , Ebbsjö Ingvar , Kalia Rajiv K. , Vashishta Priya 
Published: April 2011

AbstractUsing the molecular dynamics (MD) method, we have studied the effect of pressure on the distribution of rings and their relationship to intermediate range correlations manifested as the first sharp diffraction peak (FSDP) for Si02 glass. A systematic analysis of the modifications observed in the FSDP for densities ranging from 2.0 to 3.2 g/cm3 and temperatures from 0 to 1500 K is reported. The decrease in the height of the FSDP with increasing density is found to be proportional to the decrease in the number of 6-fold rings. For the density and temperature ranges studied in SiO2 glass, the full width at half maximum (FWHM) of the FSDP remains unchanged.
Atomistic Monte Carlo Simulations of Surface Segregation in (FexMn1-x)O and (NixCo1-x)O
Authors: Battaile C. , NajafBdi R. , Srolovitz D. J 
Published: April 2011

AbstractAn atomistic Monte Carlo (MC) method has been used to predict equilibrium segregation of isovalent cations to (001) surfaces in (Fex.Mn-x)O and (NixCol-x)O. The surface is found to be enriched with solvent in both systems. Long-range electrostatic interactions and atomic motions that occur on small time scales make the MC approach very computationally demanding. The Free Energy Minimization (FEM) method is a more efficient alternative for performing such segregation simulations, but involves several approximations. Comparison of the surface segregation profiles determined using the MC and FEM simulation methods show that the two are essentially indistinguishable. The FEM results can be obtained about 1,000 times faster than the MC predictions. Therefore, the FEM method is a practical and accurate alternative to the more cumbersome MC approach.
Tight-Binding Initialization for Generating High-Quality Initial Wave Functions: Application to Defects and Impurities in GaN
Authors: Neugebauer Jörg , Walle Chris G. Van De 
Published: April 2011

AbstractWe describe a new method that allows an efficient construction of high-quality initial wavefunctions which are required as input for iterative total-energy methods. The key element of the method is the reduction of the parameter space (number of wavefunctions) by about two orders of magnitude by projecting the plane-wave basis onto an atomic basis. We show that the wave functions constructed within this basis set are very close to the exact plane-wave wavefunctions, resulting in a rapid total-energy convergence.
Native Point Defect Densities and Dark Line Defects in ZnSe
Authors: Berding M. A. , Sher A. , Schilfgaarde M. Van 
Published: April 2011

AbstractNative point defect densities (including vacancies, antisites and interstitials) in ZnSe are calculated using a quasichemical formalism, including both vibrational and electronic contributions to the defect free energy. The electronic contribution to the defect formation free energy is calculated using the self-consistent first-principles full-potential linearized muffin-tin orbital (FP-LMTO) method and the local-density approximation (LDA). Gradient corrections are included so that absolute reference to zinc atoms in the vapor phase can be made. We find that the Frenkel defect formation energy is ∼0.3 eV lower at a stacking fault than in the bulk lattice. Nonradiative-recombination-induced Frenkel defect generation at stacking faults is proposed as a mechanism responsible for the limited device lifetimes.
First-Principles Calculations of the Elastic Properties of the Nickel-Based L12 Intermetallics
Authors: Iotova D. , Kioussis N. , Lim S. P. , Sun S. , Wu R. 
Published: April 2011

AbstractThe elastic constants of the L12-type ordered nickel-based intermetallics Ni3X (X = Mn, Al, Ga, Si, Ge), have been calculated by means of ab initio total-energy electronic structurecalculations based on the full-potential linear-muffin-tin-orbital (FLMTO) method. Theorigins in the electronic structure of the variation of the elastic constants, bulk and shearmoduli are investigated across the series, and the effects of the anisotropy of bonding chargedensity on the shear anisotropy factor and the degree of ductility is discussed.
Molecular Dynamics Simulations of a Siloxane-Based Liquid Crystal Using an Improved Fast Multipole Algorithm Implementation
Authors: McKenney Alan , Pachter Ruth , Patnaik Soumya , Adams Wade 
Published: April 2011

AbstractIn our continuing efforts towards designing materials with controlled optical properties, largescale molecular dynamics simulations of a molecular cluster of a liquid crystalline cyclic siloxane are still limited by the size of the molecular system. Such simulations enable evaluation of the orientation order parameter of the system, as well as modelling the behavior of the material in bulk. This study summarizes improvements in the implementation of the fast multipole algorithm for computing electrostatic interactions which is included in the molecular dynamics program PMD[7, 8], such as the elimination of computations for empty cells and the use of optimal interaction lists. Moreover, an improved implementation of a 3-D Fast Multipole Method (FMM3D) based on the algorithm previously proposed[1, 2] is described in detail. The structure of the module, details of the expansions, parallelization, and its integration with the molecular dynamics simulation code are explained in detail. Finally, the utility of this approach in the study of liquid crystalline materials is briefly illustrated.
First-Principles Determination Of The Effects Of Boron And Sulfur On The Ideal Cleavage Fracture In Ni3Al
Authors: Sun Sheng N. , Kioussis Nicholas , Ciftan Mikael , Gonis A. 
Published: April 2011

AbstractThe effects of boron and sulfur impurities on the ideal cleavage fracture properties of Ni3Al under tensile stress are investigated for the first time using the full-potential linearmuffin- tin-orbital (FLMTO) total-energy method, with a repeated slab arrangement of atoms simulating an isolated cleavage plane. Results for the stress-strain relationship, ideal cleavage energies, ideal yield stress and strains with and without impurities are presented, and the electronic mechanism underlying the contrasting effects of boron and sulfur impurities on the ideal cleavage of Ni3Al is elucidated.