bluuebunny/crossref_metadata_2025_split huggingface dataset:
Defect Tails in GE Implanted Si Probed by Slow Positrons and Ion Channeling
Authors: Knights A P , Nejim A , Barradas N P , Gwilliam R , Coleman P G , Malik F , Kherandish H , Romani S 
Published: April 2011

ABSTRACTPositron annihilation spectroscopy has been used to profile the distribution of defects following implantation of 120keV Ge+ into (100) Si in the dose range l x 1010 - lx104 cm−2 . The openvolume defect profiles can be adequately fitted assuming a simple rectangular block distribution extending to 350nm. Using anodic oxidation and etching, a procedure is described which allows details of the defect tails beyond the range of the implanted ion, usually inaccessible to positron -2 annihilation measurements, to be determined. For a time averaged dose-rate (Jr) of 0.02μA cm−2 and incident angle of 7°, open-volume defects are found to exist at concentrations exceeding 1016cm−3 at depths upto 600nm whereas the peak of the depth distribution of the implanted ions (Rp) is 76nm, measured using SIMS. When the time-average dose-rate is increased by a factor of 10, defects persist at concentrations in excess of 1017cm−3 beyond lμm and the Rp increases to 101nm. The open-volume defect profiles are compared to those deduced from Rutherford backscattering-channeling using the fitting routine DICADA.
Si/Ge/Si(001) Magnetron Sputter Heteroepitaxy: the Initial Stages of “Hut”- Cluster Overgrowth
Authors: Vögeli B. , Kummer M. , Känel H. Von 
Published: April 2011

AbstractWe show that the capping of Ge/Si(001) hut clusters with epitaxial Si cannot be easily realised. Even for growth temperatures as low as 300°C, Ge segregation during the Si deposition leads to a Si1-xGex alloy in both the wetting layer and the clusters which reduces the misfit of the system. In turn it is no longer beneficial to release the strain energy by forming small islands. On the contrary, there appears to be a metastable state for exhibiting a flat surface. Thus we find a 3D to 2D transition which at low Si coverages is probably thermally activated. At higher coverages, however, the transition becomes a barrier-less, resulting in the complete dissolution of the hut clusters. Annealing experiments prove that the resulting 2×8 reconstructed Si1-xGex surface is not in thermodynamic equilibrium. During the melting of a hut cluster a number of new facets are formed, mainly at the edges of the clusters and at the top, where the apex becomes substituted by a {001} facet. Our results emphasize that the melting of the Ge/Si(001) hut clusters is a serious obstacle to their application, e. g. in electroluminescence devices. It has to be solved, e. g. by the use of surfactants.
Role Of Surface Instability And Anisotropy On Strain Relaxation Of Sige On Si(110)
Authors: Deng X. , Krishnamurthy M. 
Published: April 2011

AbstractSiGe alloys (< 1.5 % mismatch) were grown on Si (110) substrates at 700°C by molecular beam epitaxy. The structure and surface morphology were studied as a function of SiGe coverage (1.5mn–9nm) using atomic force microscopy, transmission electron microscopy and RHEED. A very high density of nanoscale SiGe ledges (less than 1 nm high and 1 μm long) were observed to form on the step terraces created during buffer layer growth. An interesting phenomenon is that the step bunches generated by the buffer growth and SiGe ledges are aligned along the elastically hardest <111> direction on the Si (110) surface. With increasing alloy thickness, the nanoscale SiGe ledges become longer and straighter. The effects of the surface instability and elastic anisotropy on the elastic relaxation effects are discussed.
Comparative Growth Kinetics Of Sige In A Commercial Reduced Pressure Chemical Vapour Deposition Epi Reactor And Anomalies During Growth of Thin Si Layers on Sige
Authors: Caymax Matity , Loo Roger , Brijs Bert , Vandervorst Wilfried , Howard David J , Kimura Kenji , Nakajima Kaoru 
Published: April 2011

AbstractA short discussion about growth kinetics of Si and Si1-xGex, epitaxial layers in a reduced pressure CVD reactor using both dichlorosilane and silane is presented. Through careful observations of the growth of very thin Si layers on SiGe, an anomaly in the Si growth ratewas detected such that the thinner the Si layer, the higher the Si growth rate on SiGe. Due to the difficult nature of very thin film characterization, several analysis techniques were used. A possible explanation based on TEM observations is put forward.
Characterizations Of Zr/Si1-x-yGexCy After Rapid Thermal Annealing
Authors: Aubry-Fortuna V. , Barthula M. , Meyer F. , Eyal A. , Cytermann C. , Eizenberg M. , Chaix-Pluchery O. 
Published: April 2011

AbstractIn this work, we have investigated the reaction between Zr and SiGeC alloys after Rapid Thermal anneals performed at 800°C for 5 min. The interactions of the metal with the alloy have been investigated by X-Ray diffraction. Four crystal X-Ray diffraction was also performed to measure the residual strain in the epilayer. The final compound of the reaction is the C49- Zr(Si1-xGex)2 phase. The C49 film contains the same Ge concentration as in the as-deposited Si1-x-yGexCy layer. This suggests that no Ge-segregation occurs during annealing. Only a small strain relaxation is detected in the unreacted SiGe epilayer during the reaction. The addition of C in the epilayer prevents any strain relaxation. These results are in contrast with those observed in systems with Ti and Co, and show that the system Zr-Si-Ge is much more stable. Schottky barrier heights have been also measured: annealing leads to a slight decrease of the barrier without any degradation of the contact. The resistivity of the C49 film is about 80 μΩcm. These results indicate that Zr may be a good candidate for contacts on IV-IV alloys in term of thermal stability.
Evidence of InterDiffusion Effect In Stacked Polycrystalline Sige/Si Layers For Cmos Gate Application
Authors: Hernandez C. , Campidelli Y. , Sagnes I. , Henrisey E. , Martin F. , Bensahel D. 
Published: April 2011

AbstractPoly-SiGe stacked gates with Ge content ([Ge])varying between zero and 100% have been fabricated using an industriel single-wafer machine. These poly-SiGe layers were characterised and fully integrated in a 0.18 pm CMOS process. Interdiffusion of Si and Ge upon subsequent annealing of the structure has been observed and studied. This interdiffusion effect was found to be responsible for the discrepancy observed between theoretical and practical values of the Ge workfunction ɸms evaluated from our electrical measurements and from those of different authors. A technique for the limitation of this interdiffusion effect has then been developped and is described.
Monolithic Integration of III-V Microcavity Leds on Silicon Drivers using Conformal Epitaxy
Authors: Gérard B. , Marcadet X. , Etienne P. , Pribat D. , Friedrich D. , Eichholz J. , Bemt H. , Hanssen H. , Carlin J-F. , Ilegems M. 
Published: April 2011

AbstractConformal epitaxy is an epitaxial growth technique capable of yielding low dislocation density III-V films on Silicon. In this technique, the growth of the III-V material occurs parallel to the silicon substrate, from the edge of a previously deposited III-V seed, the vertical growth being stopped by an overhanging capping layer. As an example, conformal GaAs layers on Silicon, presenting dislocation densities below 105cm−2, have been obtained using selective vapor phase epitaxy. These layers have then been used as high quality GaAs on Si substrates for subsequent vertical MBE regrowth of active structures. In this paper, we report on the integration of surface-emitting microcavity LEDs with their silicon drivers using this conformal growth technique. The global technology concept and the design of the active structures are first presented. The compatibility of the conformal growth technique with CMOS technology is then checked: the impact of the integration process on the performances of the drivers is for example quantified. Characterisations of the high crystalline quality of the conformal layers and of the LEDs structures grown on it are then shown. The electro-optical characteristics of the LEDs on Si are finally compared to those of reference LEDs on GaAs substrates in order to prove the efficiency of the integration procedure.
FE-Modeling and Physical Testing of IGBTs for Press-Packaging
Authors: Pirondi A. , Nicoletito G. , Cova P. , Pasqualetti M. , Portesine M. , Zani P. E. , Camera A. 
Published: April 2011

AbstractThe reliability of press-packed IGBTs strongly depends on the solutions adopted in terms of heat dissipation and thermo-mechanical stress management so as to guarantee satisfactory electrical and thermal contact conditions throughout the service life. In this paper, two aspects concerning the design process of a single-chip press-pack IGBT are outlined: i) cyclic stresses and strains occurring in the package and in the chip are discussed on the basis of finite element (FE) simulations, ii) a testing rig developed for accelerated testing of single IGBT chips under controlled contact pressure conditions is presented.
Kinetic Modelling Of The Selective Epitaxy Of GaAs On Patterned Substrates By Hvpe. Application to the Conformal Growth Of Low Defect Density GaAs Layers On Silicon
Authors: Gil-Lafon E. , Napierala J. , Castelluci D. , Pimpinelli A. , Gérard B. , Pribat D. 
Published: April 2011

AbstractThe selective growth of GaAs by HVPE was studied on (001), (110), (111)Ga and (111)As, GaAs patterned substrates by varying the I1I/V ratio. A kinetic modelling of the growth was developed, based upon the SEM observations of the growth morphologies as well as on experimental curve synthesis. The growth rate is written as a function of the diffusion fluxes of the adsorbed AsGa and AsGaCI molecules and takes into account the chlorine desorption by H2. 1.5 μm thick GaAs films were then fabricated on Si (001) by a confined epitaxial lateral overgrowth technique. These conformal films exhibit intense and uniform luminescence signals, showing that the dislocation densities of GaAs are lower than 105 cm−2. SEM analyses reveal that conformal growth fronts consist in (110) and (111)As A planes under the III/V ratios (superior to 1) which were tested.
Unique Defect-Induced Donor Structure at the Lattice Mismatched InAs/GaP Heterointerface
Authors: Gopal V. , Chen E.-H. , Kvam E. P. , Woodall J. M. 
Published: April 2011

AbstractWe have investigated the direct growth of narrow-gap InAs on wide-gap GaP by Molecular Beam Epitaxy. InAs and GaP have the largest mismatch among all the III-arsenides and the III-phosphides – 11%. A perfect epitaxial relationship is maintained between the InAs and the GaP despite the large lattice mismatch. Moreover, a reproducible defect structure with unique electronic properties is developed at the heterointerface. A point defect associated with the intersection of 90° misfit dislocations may act as an ordered, structural dopant. This dopant is fully ionized with a constant, high sheet carrier density of 1013 cm−2, independent of InAs layer thickness, and exhibits no freeze out even at 5 K. Device applications for such a system include temperature insensitive Hall sensors. We have also demonstrated high electron mobilities (over 10000 cm2/V-sec) in nominally undoped thick InAs layers grown on GaP. The explanation of this effect is presented to emphasize the exciting possibilities of band gap engineering in this system.
Annihilation Radii for Dislocations Intercepting a Free Surface with Application to Heteroepitaxial Thin Film Growth
Authors: Chang M. , Mathis S.K. , Beltz G.E. , Landis C.M. 
Published: April 2011

AbstractOne critical issue in heteroepitaxial, lattice mismatched growth is the inevitable appearance of threading dislocations which reside in the relaxing film and degrade its semiconducting properties. It has been shown in previous work that threading dislocations interact with each other through a series of annihilation and fusion reactions to decrease their density as the film thickness increases and follow a 1/h decay, where h is the film thickness. A characteristic reaction radius is associated with these interactions. In previous simulations, the reaction radius was taken to be a constant value estimated using a simple approximation based on infinite, parallel dislocation lines. Here, a continuum-based elasticity approach is taken to more accurately quantify the reaction radius by comparing the Peach-Koehler force of one dislocation acting on another at a free surface with the lattice resistance to dislocation motion. The presence of the free surface gives rise to a moderate reduction of the interaction force. Results are compared with preliminary experimental data for GaAs films grown on InP.
On Dislocation Reactions and Hardening Mechanisms in 3D Dislocation Dynamics
Authors: Zbiib H.M. , Rhee M. , Hirth J.P. , Rubia T. D. DE LA 
Published: April 2011

AbstractA 3D dislocation dynamics (DD) model for plastic deformation, which connects the macroscopic mechanical properties to the basic physical laws that govern dislocation mobility and related interaction mechanisms, has been under development. In this model there is a set of critical reactions that, basically, determine the overall results of the simulations. These reactions are annihilation, formation of jogs, junctions, dipoles, and cross-slip. In this paper we discuss these reactions and the manner in which they influence the predicted stress-strain behavior in bcc metals. In particular, the formation (zipping) and strength of dipoles and junctions, and effect of jogs, using the dislocation dynamics model are examined. The strengths (unzipping) of these reactions for various configurations are determined by direct evaluation of the elastic interaction forces.
Computational Modeling of Multiple Domain Pattern Formation
Authors: Huang Tao , Tsuji Tomohiro , Rey Alejandro D. , Kamal Musa R. 
Published: April 2011

AbstractWe propose a physical model of multiple domain nucleation and growth in order to perform the cross-scale simulation on envelope profiles of the domain and the internal structure. The model utilizes two coupled field: a nonconserved envelope vector field of the local macroscopic growth domains and a vector field of the local mesoscopic lamellae directors. The envelope evolution equation includes an envelope profile function, the domain growth and impingement kinetics, the relaxation of the envelope by a surface tension, a lowest-order nonlinear term, a noise term, and a surface diffusion term. The splay, twist and bend deformation and the interaction between lamellae and noise field are considered in the free energy density equation of the lamellar director field. Results of large-scale computer simulation are reported which are compared with experiments.
Coupled Simulations of Mechanical Deformation and Microstructural Evolution Using Polycrystal Plasticity and Monte Carlo Potts Models
Authors: Battaile C.C. , Buchheit T.E. , Holm E.A. , Wellman G.W. , Neilsen M.K. 
Published: April 2011

AbstractThe microstructural evolution of heavily deformed polycrystalline Cu is simulated by coupling a constitutive model for polycrystal plasticity with the Monte Carlo Potts model for grain growth. The effects of deformation on boundary topology and grain growth kinetics are presented. Heavy deformation leads to dramatic strain-induced boundary migration and subsequent grain fragmentation. Grain growth is accelerated in heavily deformed microstructures. The implications of these results for the thermomechanical fatigue failure of eutectic solder joints are discussed.
First-Principles Study of SI(lll) Homoepitaxy
Authors: Cho Kyeongjae , Kaxiras Efthimios 
Published: April 2011

AbstractEpitaxial growth on the Si(111) surface is studied using first-principles total-energy pseudopotential calculations. The energetics of added Si atoms essentially determines epitaxial growth modes under different growth conditions (surface temperature, Si flux rate, and surface step density). We have determined the surface adatom diffusion barriers and cluster formation energies; we use these microscopic energy parameters to address the possibilities for macroscopic morphological evolution of the surface under different conditions.
AB Initio Calculations of Point Defects in Silicon
Authors: Xie Jianjun , Chen S.P. 
Published: April 2011

AbstractWe use the ab initio plane wave pseudopotential method and the density functional theory (DFT) to study the arsenic(As)-vacancy interactions in silicon. The detailed lattice distortions surrounding the As-vacancy defect and the energetics of As-vacancy reaction around the six-fold ring are investigated. We find that the As displaces its neighboring silicon atoms outward while the vacancy attracts its neighboring atoms inward. The binding energy and the formation energy of an As-vacancy pair are 1.21 eV and 2.37 eV, respectively. Once the vacancy and As binds together, the highest migration barrier for the whole complex is 1.19 eV, which is in good agreement with the experimental measurement of 1.07 eV. The calculated activation energy for the vacancy mediated diffusion of the neutral As in silicon is 3.56 eV. The nature of the binding between As and vacancy is explained from the lattice distortions introduced by the As-vacancy complex.
Accelerating Atomistic Simulations of Defect Dynamics: Hyperdynamics, Parallel Replica Dynamics, and Temperature-Accelerated Dynamics
Authors: Voter Arthur F. , Sørensen Mads R. 
Published: April 2011

AbstractObtaining a good atomistic description of diffusion dynamics in materials remains a daunting task due to the time-scale limitations of the molecular dynamics method. We discuss new methods, derived from transition state theory, for accelerating molecular dynamics simulations of these infrequent-event processes. Two of these methods (hyperdynamics and parallel replica dynamics) have been presented previously, and are briefly reviewed here. The third, temperature-accelerated dynamics (TAD), is presented in detail. In TAD, the system temperature is raised to stimulate more rapid escape out of each potential basin, but attempted transitions are filtered to allow only those that would have occurred at the normal temperature. The characteristics of the methods are compared.
Nonlinear Response of Solids and Molecules in Intense Infrared Radiation
Authors: Pantelides Sokrates T. , Winkler Roland , Ferconil Maurizio , Alvarez J. J. Vicente 
Published: April 2011

AbstractInfrared radiation, which couples with vibrations in molecules and solids, has long been considered as a promising way to selectively control chemical reactions, materials processing, and biomedical applications. The expectation is that particular frequencies couple to specific atomic motions, in contrast to heat which imparts energy indiscriminately. The promise has yet to be fulfilled, but recent successes and the development of new lasers have rekindled interest. We report calculations of the dynamics of solids and molecules under intense infrared radiation. In solids, using a model calculation, we find that narrowly-defined “windows of opportunity” exist for resonant enhancement of impurity diffusion at moderate intensities. In molecules, using a generalization of Car-Parrinello dynamics, we find that, for very intense fields, energy absorption at normal modes is not very efficient and that selective bond-breaking may occur at nonresonant frequencies by “concerted kicks”. Finally, time-dependent density functional theory is used to show that the effect of very intense infrared radiation on atoms and molecules is to produce very high harmonics as found experimentally.
Imposing Field Boundary Conditions in MD Simulation of Fluids: Optimal Particle Controller and Buffer Zone Feedback
Authors: Li Ju , Liao Dongyi , Yip Sidney 
Published: April 2011

AbstractWe formulate a method for imposing continuous field boundary conditions on an MD simulation with little or no disturbance to its dynamics. Our approach combines the previously developed thermodynamic field estimator, which extracts macroscopic fields from particle data, with a novel procedure, optimal in the sense of least disturbance, for imposing prescribed continuum field boundary conditions on the atomistic system. By means of feedback control and assuming molecular chaos in fluids, that disturbance can further be eliminated entirely, thus providing an exact solution for general steady-state fluid problems, where the desired fields at the real boundary is achieved by adjusting actions in a region separated from the real boundary by a buffer zone.
Electronic Structure Boundary Value Problems Without All of the Atoms
Authors: Johnson H. T. , Phillips R. , Freund L. B. 
Published: April 2011

AbstractA mixed atomistic/continuum technique, in the spirit of the quasicontinuum method, is formulated and used to solve boundary value problems in strained semiconductor structures in which the mechanical fields and the local electronic structure are fully coupled. The technique is implemented by means of a standard structural mechanics finite element package. Within each element in the mesh, tight binding calculations are made for mechanical properties based on the local electronic structure. The finite element program calculates equilibrium mechanical fields based on this atom-istic constitutive information; the underlying electronic properties can then be extracted at the element level. The technique is demonstrated by examining several simple plane strain boundary value problems for coherently strained silicon.
Pressure Waves in Microscopic Simulations of Laser Ablation Leonid
Authors: Zhigilei V. , Garrison Barbara J. 
Published: April 2011

AbstractLaser ablation of organic solids is a complex collective phenomenon that includes processes occurring at different length and time scales. A mesoscopic breathing sphere model developed recently for molecular dynamics simulation of laser ablation and damage of organic solids has significantly expanded the length-scale (up to hundreds of nanometers) and the time-scale (up to nanoseconds) of the simulations. The laser induced buildup of a high pressure within the absorbing volume and generation of the pressure waves propagating from the absorption region poses an additional challenge for molecular-level simulation. A new dynamic boundary condition is developed to minimize the effects of the reflection of the wave from the boundary of the computational cell. The boundary condition accounts for the laser induced pressure wave propagation as well as the direct laser energy deposition in the boundary region.
Atomic Scale Simulation of Cross Slip and Screw Dislocation Dipole Annihilation
Authors: Rasmussen Torben 
Published: April 2011

AbstractAtomistic simulations are used to study cross slip of a single screw dislocation as well as screw dislocation dipole annihilation in Cu. A configuration space path techniquex is applied to determine, without presumptions about the saddle point, the minimum energy path of transition for cross slip. The cross slip process is that proposed by Friedel and Escaig, and the energy of the in-plane constriction initiating cross slip is determined. A minimum stable dipole height much smaller than previously inferred from experimental studies is found. Relaxed screw dislocation dipoles adopt a skew configuration due to the anisotropy of Cu. The path technique is applied to investigate annihilation of stable screw dislocation dipoles, and the energy barrier for annihilation as a function of dipole height is determined for both homogeneous and heterogeneous cross slip leading to the annihilation. The results might be used as quantitative input into meso-/macro-scopical modelling approaches which rely on parameters deduced from either simulation or experiment.