bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase Formations in Co/Si, Co/Ge, and Co/Si1−xGex by Solid Phase Reactions
Authors: Wang Z. , Chen Y. L. , Ying H. , Nemanich R. J. , Sayers D. E.
Published: September 2012

Phase formations in Co thin films (200Å in thickness) reacting with atomically clean Si(100), Ge(100), and Si0.80Ge0.20 epitaxial layer (800Å in thickness on Si(100) substrates) in UHV have been investigated. For the Co/Si system, it is found that CoSi (FeSi structure) is formed at 375°C through a very disordered CoSi phase, and the final CoSi2 phase is formed at 575°C. On the other hand, the Co5Ge7 phase was identified for the Co/Ge samples annealed at 300°C and 450°C and the final CoGe2 phase is formed at 600°C. For the Co/Si0.8 Ge0.20 samples annealed from 400°C to 600°C, Co(Si1−yGey) phases with y∼0.10 were detected, and for annealing at 700°C, only the CoSi2 phase was formed. These results indicate a preferential Co- Si reaction when annealing the Co/SiGe structure. It was also found that the sheet resistance of the reacted thin films depend strongly on annealing temperature.
Laser Induced Epitaxial CoSi2 Formation
Authors: Comrie C.M. , Hoffman V.
Published: September 2012

While it is possible to grow epitaxial CoSi2 films of a high quality using UHV technology it is much more difficult to produce films of similar quality under high vacuum and non-“clean room” conditions. Tung et al.1 have however shown that films of a good quality can be produced under these poorer conditions with the aid of a laser anneal of an appropriate power followed by a short thermal anneal. In this paper the role of the laser anneal, and of the (post laser) thermal anneal, in the production of epitaxial films is examined. It appears that the principle role of the laser anneal is to induce the epitaxial CoSi2 formation at the silicon / silicide interface, and that this epitaxial layer then acts as a seed for epitaxial film growth during the subsequent thermal anneal.
Multilevel Contact System with a Thin Silicide Reaction Controlling Interlayer
Authors: Fenske F. , Schulze S. , Selle B. , Lange H. , Wolke W.
Published: September 2012

Taking advantage of controllable interdiffusion and reaction processes by using a 50 nm thin Ti interlayer an annealing step in the temperature range from 450 to 475°C transforms the TiNiAg layer sequence on silicon into a stable final state, whereby a contamination free, homogeneous nanoscale NiSi contact layer arises with low values of the contact resistance. Intercalating a thin Ti layer the nickel silicide growth rate is lowered by 2 orders of magnitude. Low sheet resistance and a good bondability are preserved by the remaining Ni-Ag top layer sequence which does not interact during the contact formation process.
Silicon-Silicide Eutectic Composites
Authors: Ditchek Brian M. , Nguyen Quang V. , Rossoni Philip G.
Published: September 2012

Many silicides, including TaSi2, CoSi2, TiSi2and others, form eutectics with silicon. Directional solidification of melts with the eutectic composition and controlled doping of the silicon matrix results in two-phase electronic composites with oriented structures. Such composites have unusual microstructures and interesting properties resulting from the high density of Schottky junctions. In this paper, the growth, microstructure, transport properties and device applications of silicon-silicide composites are reviewed, concentrating mostly on the benchmark Si-TaSi2system. The Si-TaSi2interface, formed upon solidification, is characterized electrically as well as structurally by electron-beam induced current techniques, x-ray diffraction and high resolution TEM. It is shown that the interface is of remarkably good quality allowing the fabrication of very high quantum efficiency (80%) photodiodes and high voltage (up to 6kV) transistors.
Silicided P-N Junction Diodes Fabricated by Silicidation through Silicon Buffer Layer and Dopant Drive-Out Process
Authors: Chen W. M. , Lee J. C. , Frost M.R.
Published: September 2012

This study investigates characteristics of p-n junction diodes fabricated by silicidation through a silicon buffer layer and dopant drive-out process. The purpose of using the buffer silicon layer is to reduce silicon consumption from the Si substrate during silicidation, and thus reduce the effective junction depth. The resulting structure is suitable for elevated CoSi2 source/drain contact in a metal-oxide-semiconductor field effect transistor or a silicided polysilicon emitter in a bipolar junction transistor. It was found that boron diffusion is enhanced by these buffer layers comparing to silicided diodes without silicon buffer layers. The sheet resistance of the CoSi2/polysilicon/Si structure does not degrade as seriously as CoSi2/polysilicon/oxide structure. The diode leakage current density is higher compared to diodes without buffer layers, especially when thinner buffer layers and high temperature 1000°C anneal are used.
Electrical Conductivity of Silicides
Authors: Ottaviani G. , Nava F.
Published: September 2012

Electrical transport properties of thin film and single crystal silicides will be reviewed and discussed. The presentation will be made by considering that most of the compounds behave as metals, with the resistivity which increases with the temperature, and few of them are semiconductors. Semiconductor silicides have band-gaps which span between 0.1 and 1.2 eV for ReSi2 and IrSil.75, respectively. Several metallic silicides show, expecially in the high-temperature limit, a resistivity-temperature dependence different from the classical linearity. The deviation, related to the intrinsic properties of the compound, can be affected by the presence of structural defects and impurities. The role played of such defects on the residual resistivity at low temperature will also be considered. Anisotropic effects will be discussed in relation with the shape of the Fermi surfaces.
Tunable Infrared Detection Using Epitaxial Silicide/Silicon Heterostructures
Authors: Sagnes I. , Campidelli Y. , Chevalier F. , Bodnar S. , Renard C. , Badoz P. A.
Published: September 2012

A new silicide/silicon IR detector is presented which has the potential for multicolour detection due to the tunability of its photoresponse. This tunable internal photoemission sensor (TIPS) fabricated using the Ir/Si/ErSi2 system, consists of two back–to–back Schottky diodes separated by a thin undoped Si layer. The two metals have different Schottky barrier heights so that the depleted Si forms an asymmetrical potential barrier to the carriers photocreated in each metallic film. The photocurrent flowing between the two metallic films is therefore strongly dependent on the shape and height of the effective potential barrier that can be varied by a bias applied between the two metallic electrodes. The Ir/Si/ErSi2 photoresponse and cut–off wavelength are indeed dramatically modulated when a small bias (less than 1 volt) is applied between the Ir and ErSi2 electrodes. The quantum efficiencies, measured in the 1 to 3 μm range, are comparable to the best obtained in Schottky and SiGe/Si internal photoemission detectors. A quantitative model derived from the Fowler formalism (by taking into account (i) the hole and electron photocurrents and (ii) the wavelength dependence of the photon absorption in each metallic film) fits all the experimental data over the whole range of photon energy and applied biases. The effective barrier heights thus measured as a function of applied bias are in good agreement with those deduced from activation energy analysis of the TIPS dark current and show that the cut–off wavelength can be modulated from 2.5 μm to more than 6 μm. Finally, electrical and photoresponse measurements on Cr/Si/SiGe(p+) structures (using the same TIPS mode of operation) also demonstrate the photoresponse tunability, thus combining the TIPS tunability with the extended wavelength range of operation (up to 10 μm) of SiGe/Si detectors.
Formation of β-and α-FeSi2 Films on (100) Silicon using Fe-Si and Fe-Ti-Si Diffusion Couples
Authors: Larsen K. Kyllesbech , Lauwers A. , Maex K. , Van Rossum M.
Published: September 2012

An investigation of the influence of an intermediate titanium thin film on the silicidation reaction between an overlying iron film and the (100)-oriented silicon substrate is presented. The Fe-Ti bilayers were obtained by consecutive sputtering of a Ti layer and an Fe layer on Si substrates. In addition, single iron layers were made by sputtering for comparison with the bilayers. By subsequent rapid-thermnal processing (RTP), depending on the annealing conditions, both the semiconducting β- and the metallic α-FeSi2 thin films could be formed. The phase formation has been investigated as a function of the thickness of the titanium layer, the annealing time and temperature. In this paper the first results on iron disilicide formation through Fe-Ti-Si diffusion couples are shown. Characterisation of the FeSi2 layers using Rutherford backscattering spectrometry (RBS), channelling RBS, X-ray diffraction (XRD), sheet resistivity measurements will be presented.
Thermodynamic and Experimental Study of β-FeSi2 Lpcvd
Authors: Morand Y. , Blanquet E. , Bourhila N. , Thomas N. , Bernard C. , Madar R. , Enseeg L.T.P.C.M.
Published: September 2012

Thin films of semiconducting iron sulicide β-FeSi2 have been synthetized by Low Pressure Chemical Vapor Deposition in a cold wall reactor, starting from iron chloride and silane. Optimum experimental conditions for both iron chlorination and iron disilicide deposition have been determined by classical thermodynamic calculations. Despite the narrow range of as predicted deposition parameters, it has been possible to obtain mirror like thin films of pure polycrystalline β-FeSi2 on SiO2 substrate. The structural characteristics of the as deposited layers observed by SEM, ABS and RBS are presented together with their electronic properties.
Comparison Between Ion-Beam and Thermal-Annealing Induced Solid Phase Epitaxy in Fe-Implanted Si
Authors: Lin X.W. , Desimoni J. , Bernas H. , Liliental-Weber Z. , Washburn J.
Published: September 2012

Rutherford backscattering spectrometry and transmission electron microscopy were used to compare thermally induced solid phase epitaxy (SPE) with ion-beam induced epitaxial crystallization (IBIEC) of Fe-implanted Si (001). It was found that thermal annealing leads to both Si SPE and β-FeSi2 precipitation at 520°C, but has no visible effect at 320°C. In contrast, Si SPE and FeSi2 precipitation occur at both 320 and 520°C, when ion irradiation is introduced. The precipitates grow epitaxially as γ-FeSi2 at 320°C, but consist of both β-FeSi2 and γ-FeSi2 at 520°C. It was also found that thermal annealing at 520°C results in Fe segregation toward the surface, while IBIEC basically retains the as-implanted Fe profile.
Discrimination of Surface Textures Using Fractal Methods
Authors: Card Jill P. , Hyde J. M. , Giversen T.
Published: September 2012

This paper investigates the use of fractal metrics for discrimination of copper surface textures. Measurements of copper surfaces, using contacting profilometry, provided the raw data for the fractal analysis. The samples tested included copper foil samples and a copper lead frame, typical of those in use in plastic electronic packages. The fractal Hausdorf dimension and upper/lower ranges of fractal scale are analyzed by the coastline method and compared using Bonferroni multiple confidence limits. Metrics show significant differences between sample couplets, indicating significant precision in the fractal approach to adequately quantify surface texture qualities.
Microstructural Fractal Dimension of AISI 316L Steel
Authors: Hinojosa M. , Rodréguez R. , Ortiz U.
Published: September 2012

Fractal dimension of the microstructure of AISI 316L steel (17 Cr, 12.7 Ni, 2.1 Mo, 1. 5 Mn, 0.01 C) with different degrees of strain were obtained from Richardson plots of grain boundary perimeter against magnification. Grain boundaries were revealed using conventional metallographic techniques and measurements were taken with the aid of an automatic image analizer (Quantimet 520) attached to an optical microscope. The magnifications used were 50, 100, 200, 400, and 1000X. The samples were obtained from a 4” diameter tubing, machined according to ASTM A370 standard test method and deformed to 5, 10, 15, and 20 % tensile strain. The results show that the fractal dimension of the grain boundaries changes as deformation is imparted to the material.

These results suggest that fractal dimension may be used to describe microstructural evolution of metals during deformation processes.
The Influence of Crystallographic Orientation of the Crack Plane and Crack Front on the Fracture of Tungsten Single Crystals
Authors: Glebovsky V. , Fishmeister H. , Riedle J. , Semenov V. , Gumbsch P.
Published: September 2012

For fracture studies on oriented W monocrystalline specimens it is necessary to produce very sharp, stopped precracks, which presents difficulties in the case of W. The experimental procedure and technique to produce precracks is described. The fracture experiments gave strong indications for a preference of the {100} plane as cleavage plane. It was found that the {110} planes successfully resist crack propagation, although they are the planes with the lowest surface energy. The appearance of the {121} plane as a cleavage plane in our experiments makes further studies with oriented W monocrystalline samples necessary.
Critical Cluster Size: Island Morphology and Size Distribution in Submonolayer Epitaxial Growth
Authors: Amar Jacques G. , Family Fereydoon
Published: September 2012

The island-size distribution scaling function fi (u) corresponding to submonolayer epitaxial growth with critical island size i is studied via kinetic Monte Carlo simulations for i = 0, 1, 2, and 3. An analytic form for fi (u) based on a conjecture for the small-u behavior is also presented. For i = 1, the scaled island-size distribution is found to depend on island morphology. In particular, for fractal islands with i = 1 there is excellent agreement with our analytical form as well as with experiments on low temperature Fe/Fe(100) deposition. However, for compact islands with i = 1, the scaled distribution is found to deviate slightly at small u. We also find excellent agreement between our analytical form, simulations, and experiment for i =- 2 and i = 3. Good agreement between our simulation results for i = 0 and recent experiments on Fe/Cu(100) deposition is also found. Results for the scaling of the island-density as well as crossover scaling forms for the transition from i = 1 to i = 2 and from i = 1 to i = 3 are also presented and used to determine the one-bond activation energy and critical island size transition temperature for Fe/Fe(100). The morphology of fractal islands for i = 2 is also studied and compared with experiments on Au/Ru(0001).
2-D and 3-D Electroconvection, Experiments and Models.
Authors: Fleury V. , Chazalviel J.-N.
Published: September 2012

In recent years, a lot of work has been devoted to electrochemical growth without supporting electrolyte1. A model, proposed by one of us2, predicts the existence of a positive space charge and of a large electric field in the active zones of the deposit. This leads to the existence of a coulombic force on the liquid. We show that this coulombic force triggers convective vortices in Hele-Shaw cells3,4, while it triggers vortex rings in three-dimensional cells5.We then couple the electrochemical process to the convective flow and show that, while the border between the depleted and concentrated zones has the shape of an arch in Hele-Shaw cells, it has a toroidal shape in 3-D. When many vortex rings are present, the border between the depleted and the concentrated solution is in the form of domes. We give experimental evidence of the vortex rings. (The original presentation was accompanied by a video movie which can be obtained upon request).
Formation of Self-Affine Surface During the Growth of Nickel Thin Films
Authors: Rao M.V.H. , Srinivas V. , Mathur B.K. , Chopra K.L.
Published: September 2012

Thin films of nickel deposited on various substrates have been investigated by using an STM. Topographic data recorded at different stages of the film growth reveal that the surface structure at one location of the film resemble that at another location of the same film. The repetitive structures are made up of a few coalescing clusters and forming exactly similar looking islands. As the film thickness increases, the shape and size of these repetitive patterns changes but the self-affinity of the surface structure is maintained.
Non-Linear Response of Self-Similar Electrodes and Active Membranes
Authors: Sapoval B.
Published: September 2012

We describe a simple way to compute the response of an irregular resistive interface to a Laplacian field in d=2. It permits to find the linear response of electrodes with an arbitrary geometry from the image only of the electrode. It also allows to compute the non-linear response of self similar electrodes. This method applies in principle to arbitrary irregular geometry in d=2 and it permits to predict generally that the slope of the Tafel plot is divided by the fractal dimension. These results may be transposed to the calculation of the steady state diffusion flux across an active self-similar membrane.
Step-Edge Barriers, Re-Entrant Oscillations, and Unstable Epitaxial Growth
Authors: Vvedensky Dimitri D. , Šmilauer Pavel
Published: September 2012

The influence of step-edge barriers that inhibit the interlayer transport of atoms is discussed in the context of several material systems by using simulations of a solid-on-solid model. We show how the combined effect of this step-edge barrier and a non-thermal short-range incorporation process of freshly-deposited atoms can be used to explain several epitaxial phenomena on metal and semiconductor surfaces: (i) re-entrant oscillations seen with He-atom scattering and high-resolution low-energy electron diffraction during Pt(111) homoepitaxy, (ii) instabilities during growth on GaAs(001) and several metal (001) and (111) surfaces in the form of multilayer features that dynamically coarsen, while maintining their shape, and (iii) re-entrant oscillations during etching of GaAs(001). In (iii), the incorporation is replaced by a short-range search for the atom to be removed.
When Interface Gets Rough…
Authors: Lu Toh-Ming , Yang Hong-Ning , Wang Gwo-Ching
Published: September 2012

Interface roughness is one of the central features in many important thin film technologies. Roughness is a result of far from equilibrium dynamic growth process and is difficult to describe using conventional statistical mechanics. Recently a dynamic scaling hypothesis has been proposed to describe such a system in which both time and space scaling are considered simultaneously. This approach has generated tremendous interest, both theoretical and experimental, for scientists working in thin film growth/etching as well as many diverse fields. In this paper we shall discuss the origin of the formation of interface roughness, the difference between near equilibrium and far from equilibrium growth problems, the relevant parameters that are necessary to describe a rough interface, and the application of the self-affine scaling concept in growth problems. The experimental approaches to study rough interfaces and growth fronts using diffraction will be summarized. It is shown that there exist two types of dynamic scaling during growth, one with a stationary local slope and another one with a nonstationary local slope. Future directions in this new area of research are highlighted.
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

Atomic 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

We 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

We 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

Roughness 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

Surface 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

The 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

The 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

Generalized 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

Diffusion-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

Higher 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

Extruded 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

We 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

The 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

The 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.
Sedimentation to Form Rough, Quasi-One-Dimensional Interfaces
Authors: Maher James V. , Levent Kurnaz M.
Published: September 2012

Sedimentation can result in the growt h of rough interfaces. Although sedimentation has been widely investigated in various areas of geology and engineering, the rough interface aspect of sedimentation is still unstudied. Since hydrodynamic forces are in principle long range, rough interfaces formed through sedimentation provide a significantly different growth situation for comparison with other studies of apparently similar final interfaces. This leads us to the question of the possible existence of universal phenomena in sedimentation and if there are universal phenomena, can one use noise plus a simple growth law to explain them?
Interaction Laws and the Detachment Effect in Granular Media
Authors: Luding S. , ClÉment E. , Blumen A. , Rajchenbach J. , Duran J.
Published: September 2012

We 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

We 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

During 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

New 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

The 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

Irradiation 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

The 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

Raman 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

Delta-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

A 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

200 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.
Amorphization Mechanisms in AlxGa1-xAs
Authors: Lagow B. W. , Turkot B. A. , Robertson I. M. , Rehn L. E. , Baldo P. M. , Roh S. D. , Forbes D. V. , Coleman J. J.
Published: September 2012

Bulk ion implantations of AlxGa1-xAs (x = 0.6 or 0.85) were performed at 77 K with 1.5 MeV Kr+, 1 MeV Ar+ or 1.5 MeV++ ions, and the resulting damage state examined by using Rutherford backscattering spectrometry-channeling at 77 K and 293 K and transmission electron microscopy at 300 K. Amorphization of a portion of the A1xGa1-x As layer occurred at 77 K only for the 1.5 MeV Kr+ implantation, although the dose required to cause amorphization was higher for the higher Al content alloy. TRIM calculations[10–11] show that with this implantation the density of high energy density cascades varies as a function of depth through the layer and that these are superimposed on a high, uniform density of defects. Comparison of the ion channeling spectra at 77 K and 293 K shows that recovery occurs over a portion of the layer in the Al0.6Ga0.4As but is not detected in the A10.85Ga0.15As layer. In both alloys, the room temperature microstructure consists of an amorphous and a crystalline region. The amorphous region extends from the deeper AlxGa1-xAs/GaAs interface into the layer, and is separated from the crystalline material by a crystalline region containing planar defects. The difference between the alloys is in the extent of this latter region, which decreases in width with increasing Al content. These results will be used to examine current models for amorphization in the AlxGa1-xAs system.
Fabrication of Multi-Level Buried Oxide Layers by Oxygen-Ion-Implantation into Si/Ge multilayers
Authors: Ogino Toshio , Kobayashi Yoshihiro , Prabhakaran Kuniyil , sumitomo Koji
Published: September 2012

We propose a novel technique based on preferential oxidation of Si in the Si/Ge system. Oxygen ions were implanted at 30 keV into Si/Ge multilayers while the substrate temperature was kept below 100°C. Significant oxygen concentration was then observed at the Si/Ge interfaces and at a thin Si layer embedded into the Ge layer. When the samples were then annealed above 400°c, the bonding state of the Si oxide approached that of SiO2. During this process, Ge atoms were expelled from the oxide layers. Transmission electron microscopy confirmed that silicon dioxide layers were formed. This new technique can be used to form semiconductor/insulator multilayered structures from Si/Ge multilayers.
Interaction of Cavities and Dislocations in Semiconductors
Authors: Follstaedt D. M. , Myers S. M. , Lee S. R. , Reno J. L. , Dawson R. L. , Han J.
Published: September 2012

Transmission electron microscopy of He-implanted Si-Ge and InGaAs shows an attractive interaction between cavities and dislocations. Calculation indicates that cavities are attracted to dislocations through surrounding strain fields, and strong binding (100s of eV) occurs when a cavity intersects the core. In a strained SiGe/Si heterostructure, He implantation enhances relaxation rates, and cavities bound to misfit dislocations show evidence of increasing relaxation at equilibrium by lowering dislocation energies. The interaction is expected for all crystalline solids, and gives insight into voids in GaN/sapphire and bubbles in He-implanted metals.
Vacancy-Type Defects in Electron and Proton Irradiated II- VI Compounds
Authors: Brunner S. , Puff W. , Mascher P. , Balogh A. G. , Baumann H.
Published: September 2012

In this contribution, we present a study aimed at investigating the basic properties of radiation induced defects in ZnS and ZnO and the influence of the atmosphere on the annealing characteristics of the defects. Positron annihilation experiments (both lifetime and Dopplerbroadening measurements) were performed on both single- and polycrystalline samples, irradiated with 3 MeV protons or 1 MeV electrons. For ZnS it was found that both electron and proton irradiation caused significant changes in the positron annihilation characteristics. The annealing of proton irradiated ZnS in air leads to significant oxidation and eventual transformation into ZnO.