bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Impurities On Mechanisms of Growth in Movpe GaAs
Authors: Nayak S. , Redwing J.M. , Huang J.W. , Lagally M.G. , Kuech T.F. 
Published: September 2012

AbstractAtomic force microscopy (AFM) has been used to investigate the atomic-scale mechanisms of growth of GaAs by metal organic vapor phase epitaxy (MOVPE). The influence of impurities such as silicon, oxygen and carbon on the small-scale periodic structure as well as on the large-scale features has been studied. The growth front of GaAs epitaxial films grown on vicinal GaAs (100) substrates exhibits periodic structure except for the Si doped GaAs grown on semi-insulating vicinal GaAs (100) substrates. The periodicity on the surface breaks down when oxygen, silicon or carbon concentration exceeds 1018cm−3. These impurities may preferentially attach at the step edges resulting in reduction of the mobility of the steps. At higher impurity concentrations, the motion of the growth front gets pinned on the surface resulting in a disruption of the step flow mode of growth. The wide terraces on Si doped GaAs grown on semi-insulating substrate is proposed as the kinetic limited step bunching during the step flow mode of growth.
The Diffusive Instability in Growth: DLA, Dendritic Growth, and Solidification
Authors: Sander Leonard M. 
Published: September 2012

AbstractWe give an overview of the influence of the diffusive instability in forming various growth morphologies. We review dendritic growth of crystals, and discuss the DLA model as an approach to the disordered, fractal case. We consider various systems which are reasonably well described by DLA including island shapes in surface growth.
Temperature Dependence of Surface Morphology of Silicon Grown on CaF2/Si by Electron Beam Assisted Mbe
Authors: Pettersson P.O. , Miles R.J. , Mcgill T.C. 
Published: September 2012

AbstractWe present the results of electron beam assisted molecular beam epitaxy (EB-MBE) on the growth mode of silicon on CaF2/Si(111). By irradiating the CaF2 surface with low energy electrons, the fluorine is desorbed, leaving an ordered array of F-centers behind. Using atomic force microscopy (AFM), we do not detect any surface damage on the CaF2 layer due to the low energy electron irradiation. The surface free energy of the CaF2 is raised due to the F-center array and the subsequent silicon layer is smoother. Using AFM and X-ray photoelectron spectroscopy (XPS), we find an optimal range of exposures for high temperature (650°C) growth of the silicon overlayer that minimizes surface roughness of the silicon overlayer and we present a simple model based on geometrical thermodynamics to explain this.We observed a similar optimal range of exposures that minimizes the surface roughness for medium (575°C) and low (500°C) growth temperatures of the silicon layer. We present an explanation for this growth mode based on kinetics.
Variations of Interfacial Roughness with Epilayer Thickness and Scaling Behavior in Si1−x,Gex, Grown on Si(100) Substrates
Authors: Ming Z. H. , Huang S. , Soo Y. L. , Kao Y. H. , Carns T. , Wang K. L. 
Published: September 2012

AbstractRoughness parameters of sample surface and buried interfaces in a series of thin layers of Si0.4 GeO.6 grown on Si(100) by molecular beam epitaxy (MBE) were measured by using the technique of grazing-incidence x-ray scattering (GIXS). The strain in the layer and the critical thickness of the film were determined from x-ray diffraction of the Si(004) peak. The roughness parameters can be described by a scaling-law with an exponent β = 0.71 for both the surface and interfacial roughness. Establishment of a scaling law thus allows a possibility of predicting the interfacial roughness as a function of the epilayer thickness.
Morphological Evolution with Layer Thickness in single crystal CeO2(110)/Si(100)
Authors: Inoue Tomoyasu , Yamamoto Yasuhiro , Satoh Masataka , Ohsuna Tetsu 
Published: September 2012

AbstractSurface morphology evolution of epitaxially grown CeO2(110) layers on Si(100) substrates is studied using atomic force microscopy (AFM) and reflection high energy electron diffraction (RHEED). The surface has a faceted structure; a stripe-appearance and triangular-shape in plan- and cross-sectional views, respectively. AFM measurements clarify that as the layer thickness increases, the cross-sectional shape changes from a gable roof shape toward trapezoidal, which is consistent with RHEED analyses. The width of the facet monotonically increases with the layer thickness, while its height saturates at ∼5 nm above 600 nm in thickness, which means that the surface approaches smooth morphology. Ion channeling analyses indicate that the thicker the layer, the better the crystalline quality at the surface.
Scaling Analysis of a- and poly-Si Surface Roughness by Atomic Force Microscopy
Authors: Yoshinobu T. , Iwamoto A. , Sudoh K. , Iwasaki H. 
Published: September 2012

AbstractThe scaling behavior of the surface roughness of a-and poly-Si deposited on Si was investigated by atomic force microscopy (AFM). The interface width W(L), defined as the rms roughness as a function of the linear size of the surface area, was calculated from various sizes of AFM images. W(L) increased as a power of L with the roughness exponent ∝ on shorter length scales, and saturated at a constant value of on a macroscopic scale. The value of roughness exponent a was 0.48 and 0.90 for a-and poly-Si, respectively, and σ was 1.5 and 13.6nm for 350nm-thick a-Si and 500nm-thick poly-Si, respectively. The AFM images were compared with the surfaces generated by simulation.
Singular Interfacial Hydrodynamics and the Dielectric Breakdown Model
Authors: Hentschel H.G.E. 
Published: September 2012

AbstractThe equations of motion for the interfacial dynamics in the dielectric breakdown model are derived. They form a set of coupled hydrodynamic equations for the interfacial curvature and growth probability in which the conserved densities are transported by a nonlocal velocity. From these equations the dynamical manner in which singularities in these conserved densities evolve can be studied both analytically and numerically. Shock-like behaviour associated with velocity attractor and repellor points on the evolving interface lead to bifurcations in the velocity field and finally to fractal structures in the curvature and growth probability in the absence of surface tension. In the presence of surface tension spatiotemporal chaos is observed.
Glass Transition Singularities and Slow Relaxation
Authors: Odagaki T. , Matsui J. , Hiwatari Y. 
Published: September 2012

AbstractGeneralized susceptibility for the binary soft-sphere mixtures is computed for the frequency range including both the a and β peaks in a supercooled fluid phase with a superlong-time molecular dynamics simulation. It is shown that the a peak has a non-Debye type frequency dependence and the β peak is essentially of a Debye-type. The slow dynamics is analyzed on the basis of the trapping diffusion model which takes account of two types of diffusive dynamics. With the use of the coherent medium approximation, the frequency dependence of dynamical quantities are shown to agree with the observation. The primary relaxation time is shown to exponentially diverge at a certain temperature below the glass transition point, in line with the Vogel-Fulcher equation. A unified view for the Vogel-Fulcher temperature, the glass transition temperature and the kinetic transition temperature is give on the basis of the trapping diffusion model.
Concentration Influence on Diffusion Limited Cluster Aggregation
Authors: Pencea ST.C. , Dumitrascu M. 
Published: September 2012

AbstractDiffusion-limited cluster aggregation has been simulated on a square two dimensional lattice. In order to simulate the brownian motion, we used both the algorithm proposed initially by Kolb et all. and a new algorithm intermediary between a simple random walk and the ballistic model.The simulation was performed for many values of the concentration, from 1 to 50%. By using a box-counting algorithm one has calculated the fractal dimensions of the obtained clusters. Its increasing vs. concentration has been pointed out. The results were compared with those of the classical diffusion-limited aggregation (DLA).
Elastic and Lattice Dynamical Properties of Metals Studied by N-Body Potential
Authors: Kogure Yoshiaki , Kouchi O. , Doyama M. 
Published: September 2012

AbstractHigher order elastic constants and phonon dispersion relation have been calculated by using the n-body potential based on the embedded atom method. Results of second- and third-order elastic constants for Cu, Ag, and Au crystal were compared with the experimental data and the Cauchy discrepancy was discussed. A result of phonon dispersion relation for Cu crystal was also shown.
Microstructural Changes of Welded Zn-AI Alloy
Authors: Zhu Yao Hua 
Published: September 2012

AbstractExtruded eutectoid Zn-Al alloy was welded by a melt of the same eutectoid alloy. Two different microstructures were observed in the joint part and the bulk of the welded alloy. Typical dendritic structure of as cast Zn-Al alloy was observed in the joint part of the welded alloy. The bulk ofthe welded Zn-Al alloy appeared as fine grain structure. Two different metastable phases η'T decomposed from η's of chilled as cast state and η'E of extruded state were found to be unstable during early stage of ageing. A four phase transformation occurred after the decompositions of these two metastable phases of η'T. Microstructures of both joint part and bulk of the welded alloy were investigated parallely during ageing processes.
Non Universal Scaling Law Exponents in the AC Dielectric Response of Polymer-Carbon Black Composites
Authors: Hakizabera P. , Deltour R. , Brouers F. 
Published: September 2012

AbstractWe report experimental and theoretical results concerning the ac properties of polymer-carbon black (CB) composites. For these materials, the theory of percolation has to be generalised to account for the complex structure of the CB and the observation that tunnelling plays an important role close to the percolation threshold. We have extended a model of Balberg [1] relating the non-universality of the exponent t to the CB morphology, to interpret the non universality of the dynamic scaling exponents t/(s+t) and s/(s+t) in the critical ac regime observed in these composites
Properties of Conducting Polymer Interconnects
Authors: Curtis Corrine L. , Credo Grace M. , Ritchie Jason E. , Sailor Michael J. 
Published: September 2012

AbstractThe possibility of using conducting polymer dendrites as electrical connections has been explored. AC electropolymerization of dendritic conducting polymers can be used to connect two different platinum wires. The polymerization conditions were varied in order to improve morphology, strength, conductivity, and to shorten the time needed to make connections. The variables involved in this study include electrolyte and monomer concentrations and the type of conducting polymer used (3-methylthiophene and aniline). Another area of study has been the exploitation of the inherent doping and undoping properties associated with conducting polymers to store information in the connections in the form of a resistance value. To this end, the connections were doped to known conductivity values and the persistence of conductivity was monitored over time.
Hot Corrosion Mechanism of Silicon Nitride Based Ceramics Exposed to Coal Slag Containing Potassium Sulfate
Authors: Yu Z.B. , Li W.H. , Li N.F. 
Published: September 2012

AbstractThe corrosion of three kinds of silicon nitride based ceramics by static liquid potassium sulfate-coal slag immersion was investigated at high temperatures. The reaction kinetics between silicon nitride based ceramics and coal-slag-potassium sulfate was investigated, different kinetic curves were obtained at different temperatures, it was l-(l-a)1/3=kt at 1350°C and a=kt2at 1400°C. Phase composition, microstructure of the materials before and after corrosion were studied by XRD, SEM/EDAX, and EPMA etc, which lead to the following detailed corrosion mechanism: (1) oxidation of silicon nitride based ceramics by potassium salt and oxygen in air simultaneously and formation of silicon dioxide. (2) melting of as-formed silica by potassium sulfate or K-contained silicate and resulting in a silicate melt Me-K20-xSiO2, and (3) formation of a protective silica layer below the silicate melt.
Interaction Laws and the Detachment Effect in Granular Media
Authors: Luding S. , ClÉment E. , Blumen A. , Rajchenbach J. , Duran J. 
Published: September 2012

AbstractWe study granular materials using both event driven (ED) and molecular dynamics (MD) methods. In the MD simulations we implement linear as well as nonlinear forces and also hysteretic interactions. For multiple collisions the two methods show differences: MD calculations lead to weak, whereas ED methods result in rather strong dissipation, as determined through an effective restitution coefficient.
Experiments in Model Granular Media: A Study of Gravity Flows
Authors: Rajchenbach J. , Clement E. , Duran J. 
Published: September 2012

AbstractWe study the flow under gravity of a granular model system submitted to shear in a rotating cylinder. The system is confined in a vertical 2D geometry which allows visualisation of the bulk and direct measurements of the velocity and density fields. We establish the existence of scaling properties displayed by velocity and density profiles for a large range ofdifferent flow rates.
Spatial and Temporal Probes of Deformation and Fracture at Interfaces
Authors: Dickinson J. T. , Langford S. C. , Scudiero Louis 
Published: September 2012

AbstractDuring the peel of a ductile material from a rigid substrate, a number of instabilities can arise in the shape and motion of the peel front. For instance, void formation, viscous fingering, and fibril formation and bifurcation can modulate the local rate of detachment between the two materials. These fluctuations affect the rate of energy dissipation and depend directly on the micromechanics of the detachment zone. Exploiting the consequences of contact charging between dissimilar materials, we have developed sensitive methods for detecting fluctuations during interfacial failure. We have also developed a sensitive probe of ductile deformation in reactive metals and use these measurements to probe energy dissipation during interfacial failure. We present examples of chaotic behavior and discuss the relation between these results with our current understanding of energy dissipation during interfacial crack growth.
Electronic Structure and Gate Capacitance-Voltage Characteristics of MBE Silicon δ-FETs
Authors: Manzoli J. E. , Hipólito O. 
Published: September 2012

AbstractNew implementations in MBE growth techniques allow high accuracy in δ-doping profiles in Silicon crystals. In this work we present a self-consistent numerical calculations of the electronic structure of δ-FETs, field effect transistors where electric transport channel is a quasi-two-dimensional plan of Antimonide doping in a Silicon crystal. We made the calculations to the heavy and light electrons at 77 and 300K varying the gate voltage in devices with one to three coupled deltas. We obtain the effective potential, the sub-bands and respective electronic densities, basic calculations to point at optimization of the device. We made considerations on theirs DC - capacitances and free electron density spreadings to achieve the gate-voltage best performance.
Kinetics of Intrinsic and Dopant-Enhanced Solid Phase Epitaxy in Buried Amorphous Si Layers
Authors: McCallum J. C. 
Published: September 2012

AbstractThe kinetics of intrinsic and dopant-enhanced solid phase epitaxy (SPE) have been measured in buried amorphous Si (a-Si) layers produced by ion implantation. Buried a-Si layers formed by self-ion implantation provide a suitable environment for studies of the intrinsic growth kinetics of amorphous Si, free from the rate-retarding effects of H. For the first time, dopant-enhanced SPE rates have been measured under these H-free conditions. Buried a- Si layers containing uniform As concentration profiles ranging from 1–16.1 × 1019 As.cm-3 were produced by multiple-energy ion implantation and time resolved reflectivi[ty was used to measure SPE rates over the temperature range 480–660°C. In contrast to earlier studies, the dopant-enhanced SPE rate is found to depend linearly on the As concentration over the entire concentration range measured. The SPE rate can be expressed in the form, v/vi(T) = 1 + N/[No exp(−Λ E/kT)], where vi(T) is the intrinsic SPE rate, N is the dopant concentration and No = 1.2 × 1021 cm-3, ΔE = 0.21 eV.
Heat and Mass Transport Induced by Collision Cascades
Authors: Carol A. , Alurralde M. , Saliba R. , Carol M. 
Published: September 2012

AbstractIrradiation of materials with energetic particles produces changes in the microstructure that affect mechanical properties. In previous work we studied the thermal aspects of the quenching of collision cascades that involve nanoscale phase transitions between the solid and the liquid states of the target. In this work we present a rigorous treatment of these phenomena, including a detailed description of the Stefan problem in three dimensions and diffusion in thermal gradients. This approach is oriented to give a quantitative description of the influence of the primary knockon spectrum on the microstructure short after the quenching of the heat spike.
Effects of Vacancy-Type Defects on Electrical-Activation of P+ Implanted into Silicon
Authors: Watanabe M. , Kitano T. , Asada S. , Uedono A. , Moriya T. , Kawano T. , Tanigawa S. , Suzuki S. , Ohdaira T. , Mikado T. 
Published: September 2012

AbstractThe effects of vacancy-type defects induced by ion implantation on the electricalactivation of implanted phosphorus by rapid thermal annealing (RTA) are investigated using the positron annihilation technique, secondary ion mass spectroscopy (SIMS) and the spreading resistance (SR) method. P+ ions are implanted into bare Si wafers and into Si through SiO2 films at 700 keV with doses of the order of 1×1013 cm-2. After implantation, rapid thermal annealing (RTA) is performed at temperatures between 600 and 1100 °C for 20 sec. The result shows that vacancy-type defects compensate the electrical-activation of P implanted into Si and also recoiled- oxygen is affected on the electrical-activation of P. The species of main defects for compensating the electrical-activation is identified as a divacancy (V2) from the lifetime of positrons. Effects of recoiled oxygen on the electricalactivation are attributed to the formation of vacancy-oxygen complexes just below the SiO2/Si interface and a resultant decrease in the diffusion length of vacancy-type defects.
Raman Spectroscopy of Ion-Implanted Silicon
Authors: Tuschel David D. , Lavine James P. 
Published: September 2012

AbstractRaman spectroscopy is used to characterize silicon implanted with boron at a dose of 1014/cm2 or less and thermally annealed. The Raman scattering strengths and band shapes of the first-order optical mode at 520 cm-1 and of the second-order phonon modes are investigated to determine which modes are sensitive to the boron implant. The asimplanted samples show diminishing Raman scattering strength as the boron dose increases when the incident laser beam is 60° with respect to the sample normal. Thermal annealing restores some of the Raman scattering strength. Three excitation wavelengths are used and the shortest, 457.9 nm, yields the greatest spectral differences from unimplanted silicon. The backscattering geometry shows a variety of changes in the Raman spectrum upon boron implantation. These involve band shifts of the first-order optical mode, bandwidth variations of the first-order optical mode, and the intensity of the second-order mode at 620 cm-1.
Transient Enhanced Diffusion of Boron in Silicon: the Interstitial Flux
Authors: Simpson T. W. , Goldberg R. D. , Mitchell I. V. , Baribeau J.-M. 
Published: September 2012

AbstractDelta-doped boron marker layers in silicon have been used to test further the relationship between B transient enhanced diffusion (TED) and the flux of silicon interstitials released during the annealing stage following self implantation. We present new data which address a number of questions raised by the present models. We show that in our experiments bulk trapping of interstitials is significant only for low implant fluences (∼1012 cm −2). The origin of the observed diffusion-like profiles for the interstitial flux is instead found to lie in local trapping within the δ-doped layers themselves. Boron trapped in immobile clusters may be associated with Si interstitials in approximately a 1:1 ratio; nevertheless this trapping contribution alone may not entirely account for the observed gradient. We suggest that some part of the observed TED response with depth is attributable to local trapping of silicon interstitials within the boron doped layers.
Ion Beam Induced Epitaxial Regrowth and Interfacial Amorphization of Compound Semiconductors
Authors: Glaser E. , Fehlhaber T. , Schulz R. , Bachmann T. , Gaiduk P. 
Published: September 2012

AbstractA review of MeV-ion beam induced crystallization (IBIEC) and interfacial amorphization (IBIIA) in III-V compounds (GaAs, InAs, GaP, InP) is given. The kinetics of IBIEC and IBIIA is studied as a function of the temperature, the density of the displacements v, and the ion dose rate j. Reversal temperatures TR for IBIEC ↔ IBIIA transitions are determined for the different materials showing characteristic dependences on v and j. The IBIEC rate is shown to be controlled by point defect diffusion towards the a/c-interface and additionally modified by the interface structure. The suppression of microtwin and stacking fault formation during IBIEC is explained by the fact that the ion beam modifies the orientation dependence of the crystallization kinetics avoiding the disintegration and (111)-faceting of the (100)-interface. For all the compound materials investigated the IBIEC process is stopped above critical temperatures and doses. The capture of diffasing defects by crystallites growing in the amorphous layers is considered to be responsible for the stopping of the IBIEC interface. Ways are demonstrated to avoid stopping, to achieve complete epitaxial regrowth also of thick layers, and to minimize the generation of stable damage in the crystallized layers. The limited temperature ranges for undisturbed IBIEC and IBIIA in III/V-compounds are explained by low nucleation barriers and high growth rates both of crystallites and of amorphous zones.
Characterization of Laterally Selected Si Doped Layer Formed in GaAs Using a Low-Energy FIB-MBE Combined System
Authors: Nakayama H. , Yanagisawa J. , Wakaya F. , Yuba Y. , Takaoka S. , Murase K. , Gamo K. 
Published: September 2012

Abstract200 eV and 30 keV Si2+ FIB were implanted in an MBE-grown GaAs layer in a dose range of 1012 and 1013 cm-2. Successive overlayer regrowth of the GaAs cap layer and postannealing at 800 °C for 3 – 30 s was performed to form buried thin δ-doped like layers. From the measurement of the sheet carrier density and the mobility, it was observed that doped layers had a carrier density ranging from 5×1011 to 1×1013 cm-2 and mobilities which were almost the same order in magnitude as that of an MBE-grown δ-doped sample.