bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural Characterisation of Iron-Copper Multilayers Using Transmission Electron Microscopy
Authors: Lloyd S. J. , Somekh R. E. , Dunin-Borkowski R.E. , Stobbs W. M. 
Published: September 2012

AbstractCoherent iron-copper multilayers of a wavelength of 2.5nm that were measured to be nonmagnetic were structurally characterised using high resolution and Fresnel techniques. A measurement of the tetragonal distortion from layer to layer and as a whole would allow an assessment of the degree to which the material exhibits any anomaly in its elastic behaviour. The modelling of the distortions requires however the measurement of the abruptness of the interfaces and this requires the quantification of the Fresnel contrast. The degree to which the measurements can be obtained to the required accuracies is considered.
Aging and Glassy Dynamics in Complex Systems: Some Theoretical Ideas
Authors: Bouchaud Jean-Philippe 
Published: September 2012

AbstractWe discuss some recent experimental results on the non-stationary dynamics of spin-glasses, which serves as an excellent laboratory for other complex systems. Inspired from Parisi's mean-field solution, we propose that the dynamics of these systems can be though of as a random walk in phase space, between traps characterized by trapping time distribution decaying as a power law. The average exploration time diverges in the spin-glass phase, naturally leading to time-dependent dynamics with a charateristic time scale fixed by the observation time tw itself (aging). By the same token, we find that the correlation function (or the magnetization) decays as a stretched exponential at small times t ≪ tw crossing over to power-law decay at large times t ≫ tw. Finally, we discuss recent speculations on the relevance of these concepts to real glasses, where quenched disorder is a priori absent. Keywords: Aging, slow dynamics, spin-glasses, glasses.
Characterizing Fractal and Hierarchical Morphologies Beyond the Fractal Dimension
Authors: Blumenfeld Raphael , Ball Robin C. 
Published: September 2012

AbstractWe present a novel correlation scheme to characterize the morphology of fractal and hierarchical patterns beyond traditional scaling. The method consists of analysing correlations between more than two-points in logarithmic coordinates. This technique has several advantages: i) It can be used to quantify the currently vague concept of morphology; ii) It allows to distinguish between different signatures of structures with similar fractal dimension but different morphologies already for relatively small systems; iii) The method is sensitive to oscillations in logarithmic coordinates, which are both admissible solutions for renormalization equations and which appear in many branching patterns (e.g., noise-reduced diffusion-limited-aggregation and bronchial structures); iv) The methods yields information on corrections to scaling from the asymptotic behavior, which is very useful in finite size analysis. Markovian processes are calculated exactly and several structures are analyzed by this method to demonstrate its advantages.
Laser Scanning of Natural and Artificial Snow Packs
Authors: Itagaki Kazuhiko , Lemieux G.E. , Ji Nina 
Published: September 2012

AbstractIn an effort to numerically describe a snow pack as a disordered aggregate of irregularlyshaped particles, a new optical analysis system was conceived. The system measures light transmission through snow samples impregnated with an opaque fluid. The analysis of the results is presented.
Fracture and Fractals in Glasses
Authors: Chechetkina Elena A. 
Published: September 2012

AbstractOriginal model of bond waves is atpplied to the problem of fracture in glasses when considering it from the fractal point of view. Bond waves are assumed to be traveling above Tg, the glass transition temperature, and frozen in solid material(T<Tg), and just alone the stopped wavefronts (WF) populatedwith weakened bonds the fracture occurs. Crack, initiating at a given WF, then develops along WF's belonging to this system (a given bond wave) and/or another set (coexisting bond wave), and may oscillate between them. The arising surface represents a natural fractal whose fractal dimension depends on the mode of bond waves interaction and their arrangement relatively to the crack direction.
Cooperative Strategies and Genome Cybernetics in Formation of Complex Bacterial Patterns
Authors: Ben-Jacob Eshel , Shochet Ofer , Cohen Inon , Tenenbaum Adam , CzirÓk Andras , Vicsek Tamas 
Published: September 2012

AbstractWe present a study of interfacial pattern formation during growth of bacterial colonies. Growth of bacterial colonies bears similarities but presents an inherent additional level of complexity in comparison with non-living systems. In the former case, the building blocks themselves are living systems, each with its own autonomous self-interest and internal degrees of freedom. The bacteria have developed sophisticated communication channels, which they utilize when growth conditions are tough. Here we present a non-local communicating walkers model to study the effect of local bacterium-bacterium interaction and communication via chemotaxis signaling. We demonstrate how communication enables the colony to develop complex patterns in response to adverse growth conditions. This self-organization of the colony, which can be achieved only via cooperative behavior of the bacteria, may be viewed as the outcome of an interplay between the micro-level (the individual bacterium) and the macro-level (the colony). Some qualitative features of the complex morphologies can be accounted for by invoking ideas from pattern formation in non-living systems together with a simplified model of chemotactic “feedback”.
Wavelet Based Structural Analysis of Electroless Deposits in the Diffusion Limited Regime
Authors: Arneodo A. , Argoul F. , Kuhn A. , Muzy J.F. 
Published: September 2012

AbstractWe discuss the actual relevance of thin gap geometry electrodeposition to generate fractal patterns that mimic the morphology of Witten and Sander's diffusion-limited aggregates (DLA). Eliminating migration and convection, as well as electrochemical side reactions, we show that electroless deposition is a good candidate to meet the requirements for diffusion to be the rate limiting step of the growth process. We use the wavelet transform microscope to achieve a comparative structural characterization of both experimental electroless deposits and numerical DLA clusters. The fact that five-fold symmetry and Fibonacci hierarchical ordering are found as common predominant statistical features is, to our knowledge, the first demonstration, relying on an appropriate structural fractal analysis, of the existence of DLA morphologies in an experimental context.
Kinetic and Equilibrium Cluster-Size Distributions of Antibody-Antigen-Induced Colloidal Aggregation
Authors: Sherman Derin A. , Cohen Richard J. 
Published: September 2012

AbstractOur colloidal system is composed of antigens covalently coupled to polystyrene microspheres. When monoclonal antibodies are added to solution, they reversibly bind to the antigens causing aggregation. Unlike many other similar systems, our system is thermodynamicallyreversible: the aggregates will dissociate in the presence of free antigen, and the aggregation process reaches a state of thermodynamic equilibrium. This system is of interest as it can be used to model many different chemical, physical and biological processes. In particular, this system can be used to quantify the interactions between the biomoleculesattached to the microspheres1 and also to explore the statistical mechanics of reversible particle aggregation.
Structure Factor Scaling in Fractal Aggregation of Colloidal Clusters
Authors: Ramírez-Santiago Guillermo , González Agustín E. 
Published: September 2012

AbstractWe report the observation of spatial ordering of clusters that leads to a spinodal-type scaling of the structure factor S(q), in the 3D simulations of diffusion-limited colloid aggregation. We are able to clearly identify the peak in S(q) as arising from the correlation between particles belonging to nearest neighbor clusters. The S(q) has a terminal shape that corresponds to a close-packing of the clusters after gelation, in a concentration range larger than the one found in recent experiments.PACS numbers: 02.70.-e, 05.40.+j, 64.60.Qb, 81.10.Dn
Dynamics of Granular Materials: Flows, Relaxation and Convection
Authors: Hong Daniel C. , Yue Su , Kurtze Douglas A. 
Published: September 2012

AbstractUsing the diffusing void model of granular flows, we study the dynamic response of granular materials, in particular, the relaxation of granular pile, pipe flow of granular materials, and the convection of granular media in a two dimensional box subjected to vibrations. We first study the relaxation of a one dimensional granular pile of height L in a confined geometry under repeated tapping within the context of the diffusing void model. The reduction of height as a function of the number of taps is proportional to the accumulated void density at the top layer. The relaxation process is characterized by the two dynamic exponents z and z' which describe the time dependence of the height reduction, Δh(t) ≈ tz and the total relaxation time, T(L) ≈ Lz'. While the governing equation is nonlinear, we find numerically that z=z'=l, which is robust against perturbations and independent of the initial void distributions. We then show that the existence of a steady state traveling wave solution is responsible for such a linear behavior. Next, we examine the case where each void is able to maintain its overall topology as a round object that can subject itself to compression. In this regime, the governing equations for voids reduce to traffic equations and numerical solutions reveal that a cluster of voids arrives at the top periodically, which is manifested by the appearance of periodic solutions in the density at the top. In this case, the relaxation proceeds via a stick-slip process and the reduction of the height is sudden and discontinuous. We then carry out the long wave analysis to demonstrate the existence of the KdV solitons in the traffic equations. Finally, we show our preliminary studies on granular convection in a box. We observe the appearance of two rolls when the control parameter exceeds the critical value, which then undergoes bifurcations to four rolls.
Direct Observation of Size Segregation: Convection and Arching Effect
Authors: Duran J. , Mazozi T. , Clement E. , Rajchenbach J. 
Published: September 2012

AbstractWe report an experimental study of the ascent of a large disc imbedded in a 2D packing ofsmall beads vertically vibrated. Two distinct mechanisms leading to size segregation are observedin situ. At high acceleration, the convection process associated with surface trapping is predominates. At low acceleration, we examine the effect of the size ratio on the dynamics of the segregation which is either intermittent or continuous. This isdue to the successive formation and destruction of arches.
Id Excited Granular Media: Clustering and Equation of State
Authors: Williams D.R.M. , Mackintosh F.C. 
Published: September 2012

AbstractWe study a one-dimensional granular system, excited by white noise, with inelastic interactions between the particles. When the coefficient of restitution,η, is one, the particles are totally uncorrelated. As η decreases the particles cluster. A computer simulation of the system shows equilibrium clustering with a power law particle-particle correlation function. This correlation function is independent of the average kinetic energy of the particles but depends strongly on η We give simple analytical arguments to describe this clustering. We also present an “equation of state” for the particles, which relates the noise amplitude to the particle density and the average particle speed.
Reversible Axial Segregation in Rotating Granular Media
Authors: Hill K. M. , Yarusso L. , Kakalios J. 
Published: September 2012

AbstractBinary mixtures of granular media having differing diameters are combined in a horizontal cylinder and rotated like a drum mixer about its long axis. Within a few minutes of rotation at 15 rpm axial segregation occurs and the mixture separates into relatively pure alternating bands of the individual components along the axis of rotation. We describe an experimental system whereby the mixed state can be restored by changing the speed of rotation. The sensitivity of the reversible axial segregation effect to systematic variations of the glass bead diameter is reported. Measurements of the dynamic angle of repose of the mixed and segregated phases support an explanation for the reversible axial segregation effect involving the competition between axial drift and diffusion currents, leading to a diffusion equation with a negative effective diffusion coefficient.
Mixing of a Granular Material in a Bidimensional Rotating Drum
Authors: Clement Eric , Rajchenbach Jean , Duran Jacques 
Published: September 2012

AbstractWe report experimental measurements on mixing properties in bidimensional rotating drum. Using an image processing device, we follow the trajectories of tracer particles in a monodisperse assembly of beads. Tracer particles with different size ratios exhibit a violent segregation effect: a smaller particle has a tendency to stay in the centre and a larger one will rather dwell on the edges. Furthermore, for a tracer of identical size, we evidence a specific dispersion property where the centre and the edges are competing attractors of the mixing dynamics.
The Geometry of Dla: Different Aspects of the Departure from Self-Similarity
Authors: Mandelbrot B.B. , Vespignani A. , Kaufman H. 
Published: September 2012

AbstractIn order to understand better the morphology and the asymptotic behavior in Diffusion Limited Aggregation (DLA), we studied a large numbers of very large off-lattice circular clusters. We inspected both dynamical and geometric asymptotic properties, namely the moments of the particle's sticking distances and the scaling behavior of the transverse growth crosscuts, i.e., the one dimensional cuts by circles. The emerging picture for radial DLA departs from simple self-similarity for any finite size. It corresponds qualitatively to the scenario of infinite drift starting from the familiar five armed shape for small sizes and proceeding to an increasingly tight multi-armed shape. We show quantitatively how the lacunarity of circular clusters becomes increasingly “compact” with size. Finally, we find agreement among transverse cuts dimensions for clusters grown in different geometries, suggesting that the question of universality is best addressed on the crosscut.
Fractal Properties of Fracture Surfaces: Roughness Indices and Relevant Lengthscales
Authors: Bouchaud Elisabeth 
Published: September 2012

AbstractExperiments aiming at the measurement of the roughness index ζ of “rapid” fracture surfaces are briefly reviewed. For rapid crack propagation, measured values of ζ are close to 0.8, which seems to be a universal exponent. However, it is argued, by re-writing the Griffith criterion for a self-affine crack, that the self-affine correlation length ξ might depend upon the microstructure, and hence on the fracture toughness. More recent experiments are also described, which reveal at smaller lengthscales the existence of a quasi-static fracture regime separated from the previously studied rapid fracture regime by a crossover length which decreases with increasing crack velocity.
Boron Transient Enhanced Diffusion in Heavily Phosphorus Doped Silicon
Authors: Huang M. B. , Myler U. , Simpson T. W. , Simpson P. J. , Mitchell I. V. 
Published: September 2012

AbstractA study has been made of B transient enhanced diffusion (TED) in heavily P-doped Si using secondary ion mass spectroscopy (SIMS) and positron annihilation spectroscopy (PAS). The Pdoped silicon was implanted with boron ions of 40 keV energy to a dose of 3 × 1014 cm-2, and then annealed at temperatures ranging from 700–1000°C in a N2 ambient for varying durations. As P doping concentration increased from 3 × 1019 to 1 × 1020 cm-3, boron diffusivity and the immobile boron fraction decreased. Our experimental results are inconsistent with the predictions of the Fermi-level model and suggest that the clustering between B atoms and Si interstitials should be invoked in order to explain the immobile portion of the B peak during TED.
An Electronic Stopping Power Model in Single-Crystal Silicon from a Few KeV to Several MeV
Authors: Morris S. J. , Obradovic B. , Yang S.-H. , Tasch A. F. , Rubin L. 
Published: September 2012

AbstractAn electronic stopping power model for boron, arsenic, and phosphorus ion implantation into single-crystal Si is reported over the energy range from a few keV to several MeV, for both offand on-axis implant angles relative to the <100> crystallographic direction. Combined with previously developed models for damage accumulation, this model allows physically-based simulation of 3-D profiles over an extremely wide range of implant conditions. In particular, this allows modeling of MeV implants which are being used more and more frequently.
Annealing Properties of Defects in BF2+ Implanted Silicon
Authors: Kitano T. , Watanabe M. , Yaoita A. , Oguro S. , Uedono A. , Moriya T. , Tanigawa S. , Kawano T. , Suzuki R. , Ohdaira T. , Mikado T. 
Published: September 2012

AbstractThe annealing properties of defects in BF2+ implanted silicon were investigated using positron annihilation, TEM and SIMS techniques. For the as-implanted specimens, the major species of defects was identified to be divacancies. After thermal annealing, vacancy-fluorine complexes were formed. The size of open volume in the vacancy-fluorine complexes became larger with increasing annealing temperature. Even after 1100 °C , the vacancy-fluorine complexes were still stable with the size of open volume close to V5. The depth profile of vacancy-fluorine complexes was not largely changed after re-crystallization. In this way, the fluorine atoms played an important role in forming the defects with a large size of open volume. After 1100°C annealing, the fluorine atoms piled up at two regions; the projected range of fluorine and the original amorphous/crystalline interface, where bubbles were observed by TEM. The vacancy-fluorine complexes detected by positron annihilation might be precursors of the bubbles observed by TEM.
Mask-Edge Distributions Produced by 80 keV As+ Ion Implantation into Si
Authors: Danailov D. , Karpuzov D. , Almazouzi A. , Almeida P. De , Victoria M. 
Published: September 2012

AbstractThe 2D-dopant and defect distributions resulting from 80 keV ion implantation of As+ ions into Si through a high-edge mask are presented. The distributions are obtained by means of an efficient computer procedure using the results of Monte Carlo simulation. Two versions of the computer code TRIM are used. The 2D-target atom redistribution is obtained as a result of cascade collisions. The simulation reveals the effect of near-mask-edge target atom depletion. This effect is related to the recoil phenomena and can be explained on the basis of simple model.
Secondary Defect Formation and Gettering in MeV Self-Implanted Silicon
Authors: Brown R. A. , Kononchuk O. , Radzimski Z. , Rozgonyi G. A. , Gonzalez F. 
Published: September 2012

AbstractSecondary defect and impurity distributions in MeV self-implanted Czochralski (Cz) and float-zone (FZ) silicon have been investigated by transmission electron microscopy, optical microscopy with preferential chemical etching, and secondary ion mass spectroscopy. We found that the ion fluence and the oxygen content of the implanted wafers affect the number and depth distribution of extended defects remaining after annealing. Intrinsic oxygen also redistributes during annealing of Cz wafers, producing two regions of relatively high oxygen concentration: one at extended defects near the ion projected range, and another, shallower region, which correlates with the distribution of vacancy-type defects. Both of these regions are also able to getter metallic impurities, depending on the implantation and annealing conditions. These defect issues may adversely affect the quality of the near surface device region, and must be controlled for successful gettering by ion implantation.
X-Ray Photoelectron Spectroscopy Investigation of the Interaction of NF3 with Silicon
Authors: Little T. W. , Ohuchi F. S. 
Published: September 2012

AbstractThe interaction of nitrogen trifluoride (NF3) with silicon (Si) surfaces has been investigated by x-ray photoelectron spectroscopy (XPS). Si (100) surfaces were subjected to NF3 ion bombardment as a means of approximating plasma processing under controlled conditions. Samples were also exposed to actual NF3 DC plasmas and the results compared to ion beam and plasma processing using nitrogen (N2). The results indicate that nitridation of silicon is possible using NF3 although it seems to be limited by simultaneous etching. Additionally, results suggest bonding between both Si-F and Si-N species and perhaps F-N-Si moieties. NF3 plasma processing has lead to curious results for F ls spectra which are not fully understood at present.
Elevated Temperature Implantation of GaAs with Si Ions.
Authors: Brown R. A. , Williams J. S. 
Published: September 2012

AbstractThe formation of amorphous layers in GaAs during ion bombardment at elevated temperatures, where dynamic annealing of radiation-induced defects is substantial, is shown to be extremely sensitive to the ion flux, fluence, and implantation temperature. For example, with increasing fluence, damage can first build up extremely slowly, then suddenly collapse to the amorphous phase. Alternatively, for a constant ion fluence, a change in flux by one order of magnitude can change the critical temperature for amorphisation by 27°C, and at constant flux and fluence, a change of only 6°C can alter the residual damage from small clusters barely visible by conventional transmission electron microscopy and Rutherford backscattering to a thick amorphous layer. The temperature at which this occurs is strongly dependent upon the ion flux and fluence.
Electron Beam Enhanced Precipitation in Highly Carbon Doped GaAs Layers
Authors: Werner P. , Gösele U. , Kohda H. 
Published: September 2012

AbstractHighly carbon doped GaAs layers grown by metal organic vapor phase epitaxy (MOVPE) have been investigated by transmission electron microscopy (TEM). Electron irradiation has been applied to generate point defects interacting with native defects, e.g., substitutional carbon. This irradiation induces periodically arranged striations perpendicular to the growth direction, which were observed in situ by TEM. Furthermore, precipitates (Ø= 10–15nm) were formed containing non-crystalline material, which most likely is gallium. To explain these phenomena a precipitation mechanism is proposed. It involves small fluctuations of the incorporated C as well as the interaction of irradiation induced point defects, mainly As and C interstitials and As vacancies.