bluuebunny/crossref_metadata_2025 huggingface dataset:
Damage in Composite Materials: Experiment Vs a Computational Chaotic Model
Authors: Meloni Franco , Varone Alberto , Ginesu Francesco
Published: March 2011

We present the results of a combined experimental and theoretical study performed using non-linear mechanics schemes to investigate the structural behaviour of a composite macroscopic material. A simple model is considered to define the order of the complexity of the real system represented by a graphite peek polymer under static and dynamic load In particular a relationship has been found between the critical points in the energy-time diagram and in the bifurcation plot.
Conventional and Unconventional Numerical Transfer-Matrix Methods
Authors: Novotny M. A. , Rikvold P. A.
Published: March 2011

We briefly review the numerical transfer-matrix (TM) method and its application to materials science. We report on the conventional use of TM methods to calculate phase diagrams and critical exponents of classical statistical mechanical models in d=2. Examples presented here are spin-1/2 and spin-1 models (two- and three-state lattice-gas models). Discussed are a model for oxygen -ordering in the high temperature superconductor YBa2Cu3O6+x and a model for the electrosorption of an organic substance on a metal. Some results for the spin-1/2 model in d=3 are also presented. Three unconventional applications of the TM method will also be reported. These include a study of the surface tension of spin-1/2 models, a TM formalism for metastability, and a study of a translationally invariant (non-fractal) spin-1/2 model in non-integer dimensions.
A Comparative Analysis of Brittle Fracture in Amorphous and Polycrystalline Materials
Authors: Calomino A. , Brewer D. , Kim A. , Chudnovsky A.
Published: March 2011

The fracture results of an amorphous epoxy resin and polycrystalline silicon nitride tested under monotonically increasing crack mouth opening displacements were compared. A conventional compact tension specimen was used for the epoxy. A new loading system and specimen was designed for the ceramic to permit stable crack growth. Tests conducted on both materials revealed multiple events of subcritical crack growth, dynamic initiation, dynamic growth, and subsequent arrest. The elastic energy release rate at initiation, G11, and arrest, G1a, was evaluated for each event. The value of G11 was found to be higher than G1a for both materials.

Also common was the systematic existence of slow growth prior to dynamic initiation. Additionally, both materials showed differences between the fracture surface morphology for slow, 10-6 m/s, and fast, 103 m/s, growth. Although a constant G1a was recorded for the epoxy, large scatter and a possible trend was recorded for G1a in the ceramic.
New Tight-Binding Pair Potentials for Mineral Oxides: Application to β-Cassiterite (110), β-Tridymite (10TO) and Cristobalite (110)
Authors: Godin T. J. , Lafemina John P.
Published: March 2011

Tight-binding, total-energy (TBTE) methods have successfully predicted surface atomic geometries for a variety of semiconducting and insulating materials that are well described by a nearest-neighbor model of interatomic interactions. However, little work has been done on distant-neighbor models, which are required to study many important mineral oxides. In this paper we demonstrate one way in which the TBTE methodology can be extended to these materials. To illustrate this approach, we calculate surface atomic structures for cassiterite SnO2 (110), β-cristobalite SiO2 (110) and βtridymite SiO2 (10TO).
Discrete Models for Particle Packings
Authors: Jagota A. , Dupont E.I.
Published: March 2011

Discrete computational models for the viscosities, sintering rates, and transport properties of sintering particle packings are presented. The packing is represented by a set of nodes (the particle centroids) connected by links (inter-particle contacts). The models for the mechanical behavior enforce equilibrium for each particle which leads to a set of simultaneous equations for the particle motion. Electrical or thermal transport through inter-particle contacts is modelled by imposing zero net flux at a node which also leads to a set of simultaneous equations for the value of potential at each particle center. The model is used to simulate the compaction of spheres to generate a threedimensional random packing. Statistical properties of the computed packing such as packing fraction, percolation threshold, and coordination number are compared with those of an experimental random packing. Results are also presented for the effective conductivity of mixtures of particles with very different conductivities.
Molecular Dynamics Investigations into the High Permeability of Siloxane Polymers
Authors: Madkour T. , Kloczkowski A. , Mark J. E. , Roe R. J.
Published: March 2011

The polysiloxanes are known to have unusually high permeabilities, and have therefore been much investigated with regard to their possible use as gasseparation membranes. In particular, their permeabilities are much higher than those of n-alkanes such as polyethylene (PE), a polymer which has already been extensively investigated using molecular dynamics simulations. In order to gain insight into the molecular origin of this high permeability, such simulations have been carried out on hypothetical model systems in which the structure of the polyethylene chain [-CH2-CH2-]x is converted step-wise into that of the most important polysiloxane, poly(dimethylsiloxane) (PDMS) [-Si(CH3)2-O-]x. The structural modifications thus investigated include (i) increase in the C-C bond length, (ii) change of the system's density from the density of PE to the density of PDMS, (iii) change of bond angles of PE to the alternate bond angles of PDMS, (iv) replacement of the torsional potential of PE by the torsional potential of PDMS, (v) change of masses of CH2 units along the chain to alternate masses of Si(CH3)2 and 0 units, (vi) change of Lennard-Jones parameters of CH2 groups for the appropriate parameters of Si and 0 units. At each of the six steps the self-diffusion coefficients of polymer segments and penetrant molecules (CO2) were calculated, allowing for the assessment of the influence of the structure of the polymer on the diffusion of the penetrant.
An Application of Flory-Huggins Lattice Theory Through Molecular Simulation
Authors: Fan Cun Feng
Published: March 2011

Fundamental parameters in the Flory-Huggins theory of binary mixture, including the heat of mixing associated with pairwise interactions ( Δw12) and the coordination number, z, are calculated through molecular simulations. The pair energies (w11, w22, w12) are obtained by averaging a large number of configurations generated by a Monte Carlo approach which includes the constraints associated with excluded volume. The temperature dependence of the interaction parameter X is obtained from this study.
Atomistic Simulation of Crystal-to-Amorphous Transitions in the Intermetallic Alloys NiZr2 and Cu3Au.
Authors: Cleri Fabrizio , Rosato Vittorio , Massobrio Carlo
Published: March 2011

The behaviour of two different systems, NiZr2 and Cu3Au, submitted to a chemical disordering process under various thermodynamical conditions has been investigated by Molecular Dynamics simulations. The role played by volume expansion and elastic softening in the onset of the transition has been discussed in the framework of the percolation model (C.Massobrio and V.Pontikis, Phys.Rev.B 45 (1992) 2484), correlating the elastic instability with the percolation of the distorted regions which establishes in the lattice as a consequence of the external perturbations (introduction of defects, volume expansion, chemical disorder etc.).
High Energy Heavy Ions Irradiation of Thermal SiO2 Films on Si
Authors: Slaoui Abdelilah , Busch Marie-Claude , Doorhyee Eric , Toulemonde Marcel , Siffert Paul
Published: March 2011

In this work, we present experimental observations of radiation damage in thermal SiO2 films grown on silicon, induced by energetic (> 0.2 GeV) O, Ni and Xe ions bombardement. The structural analysis of the SiO2 films, using infrared absorption spectroscopy, ellipsometry and etch rate measurements, points to atomic displacements, broken and strained Si-O bonds induced by irradiation. We have also estimated the damage production cross section and the track radii of the ions in the amorphous SiO2 films as a function of the electronic stopping power.
Role of Oxygen Precipitation Processes in Defect Formation and Evolution in Oxygen Implanted Silicon-on-Insulator Material
Authors: Park J. C. , Lee J. D. , Venables D. , Krause S. , Roitman P.
Published: March 2011

The role of precipitation processes in defect development in high temperature implanted single and multiple implant/anneal SIMOX was studied by transmission electron microscopy. The differences in defect type, density and location were compared. The dominant defects in single implanted and annealed material are pairs of narrow stacking faults (NSFs) at a density of ∼ 106 cm−2 while stacking fault pyramids (SFPs) at a similar density dominate multiple implant/anneal material. However, SFPs are confined to the buried oxide interface and thus the density of through-thickness defects is about two orders of magnitude lower in multiple implant (<104 cm−2) than in single implant material (∼106 cm−2). SFPs are formed from a collection of four NSFs pinned to residual oxide precipitates. This transformation is energetically possible only below a critical NSF length which is dictated by the relative location of the residual precipitates. In turn, the residual precipitate location is determined by the location of as-implanted defects on which SiO2 preferentially nucleates and grows. Thus, the synergistic interaction between precipitation and defect formation and evolution processes plays a key role in determining the final defect microstructure of SIMOX.
Stability and Relaxation of Point Defects in amorphous silicon
Authors: Lutz Raymond , Lewis Laurent J.
Published: March 2011

We have used molecular-dynamics to investigate the stability and relaxation of point defects — vacancies and interstitials — in a model of amorphous silicon, with the interactions between atoms described by the Stillinger-Weber empirical potential. The annihila-tion of point defects has been proposed as an important mechanism by which relaxation proceeds in amorphous silicon. Starting with a Wooten-Winer-Weaire model of a-Si, we “manually” create vacancies in the structure by removing a number of randomly-selected four-fold coordinated atoms. The system is then allowed to relax. Our calculations reveal unambiguously that, of a number of vacancies introduced in the model at low temperature, roughly a third are stable; these anneal out upon heating at room temperature. The vacancies seem, in most cases, to consist of a relatively large empty volume bounded by four atoms of which at least one is undercoordinated. Our study of interstitials seems to indicate that they diffuse through a “jump-and-bump” process, eventually annihilating when a large enough, properly coordinated, vacant volume is encountered.
Computer Simulation of Atomic Collision Processes in Solids
Authors: Robinson Mark T.
Published: March 2011

Computer simulation is a major tool for studying the interactions of swift ions with solids which underlie processes such as particle backscattering, ion implantation, radiation damage, and sputtering. Numerical models are classed as molecular dynamics or binary collision models, along with some intermediate types. Binary collision models are divided into those for crystalline targets and those for structureless ones. The foundations of such models are reviewed, including interatomic potentials, electron excitations, and relationships among the various types of codes. Some topics of current interest are summarized.
TiSi2 Integrity within a Doped Silicide Process Step
Authors: Crean G. M. , Cole P. D. , Stoemenos J.
Published: March 2011

Degradation of arsenic implanted titanium suicide (TiSi2) thin films as a result of thermal processing for shallow junction formation is investigated. Significant arsenic diffusion from the suicide overlayer into the silicon substrate has been detected by Rutherford Backscattering Spectrometry at drive-in temperatures > 1050°C. Cross-sectional transmission electron micrographs have shown the suicide film become increasingly non-uniform as the thermal budget increases, ultimately leading to discontinuities forming in the suicide film. This observed degradation of the titanium suicide film is also supported by sheet resistance measurements which show the film to degrade significantly above a threshold thermal budget
High-Current and Low Acceleration Voltage Arsenic Ion Implanted Polysilicon-Gate and Source-Drain Electrode Si MOS Transistor
Authors: Saito Yasuyuki , Sugimura Yoshiro , Sugihara Michiyuki
Published: March 2011

The fabrication process of high current arsenic (As) ion implanted poly-silicon (Si) gate and source-drain (SD) electrode Si n-channel metal-oxide-semiconductor field-effect-transistor (MOSFET) was examined. Poly-Si film n-type doping was performed by using high current (typical current: 2mA) and relatively low acceleration voltage (40keV) As ion implantation technique (Lintott series 3). It was observed that high dose-As implanted poly-Si films as is show refractoriness against radical fluorine excited by microwave. Using GCA MANN4800 (m/c ID No.2, resist: OFPR) mask pattern printing technique, the high current As ion implantation technique and radical fluorine gas phase etching (Chemical dry etching: CDE) technique. the n-channel poly-Si gate (ps=∼L00ft/o) enhancement MOSFETs(ps-source-drain = =50n/o, SiO2 gate=380A) with off-leak-less were obtained on 3”Czochralski-grown 2Ωcm boron-doped p-type wafers (Osaka titanium). By the same process, a 8-bit single chip μ-processor with 26MHz full operation was performed.
Trim Simulations and Possible Studies for Edge-on Ion Irradiation of Electron Microscope Specimens
Authors: Thompson Loren J. , Allen Charles W. , Frischherz Marcus C. , Otero Mauro P.
Published: March 2011

A TRIM code [1] has been modified to simulate a special technique, first described at the Spring 92 MRS Meeting [2], for in situ transmission electron microscope (TEM) experiments involving simultaneous ion irradiation, in which the resultant phenomena are observed as in a cross-section TEM specimen without further specimen preparation. Instead of ion-irradiating the film or foil specimen normal to the major surfaces and observing in plan view (i.e., in essentially the same direction), the specimen is irradiated edge-on (i.e., parallel to the major surfaces) and is observed normal to the depth direction of the irradiation. The results of calculations utilizing the modified TRIM code are presented for cases of 200 and 500 keV Co impinging onto the edge of Si films 200 and 600 nm thick. The limitations of the technique are discussed and the feasibility of experiments involving implantation of Co into Si and the formation of COSi2, which employ this technique, are briefly discussed.
Phase and Structural Transformations in Iron and Carbon Steel Induced by Megavolt High-Current Electron Beam
Authors: Efremov A. M. , Ivanov Yu. F. , Itin V. I. , Lykov S. V. , Markov A. B. , Rotshtein V. P. , Tukhfatullin A. A.
Published: March 2011

Using X-ray structural and transmission electron microscopy analyses, specific features of the phase and structure transformations in armco-iron and steel 45 affected by a high-current electron beam up to 1011 W/cm2 power density have been studied. It was revealed that hardening of steel with martensite structure has a quasi-periodic character that is caused by the action of a shock wave. The action of a shock wave results in formation of a thin layer on the rear side of the samples. The layer is composed of subgrains of ot-ferrite of a regular hexagonal shape with thin layers of graphite on their boundaries.
The Influence of Ion Beam Implantation on Electrical Properties of Polycrystalline MnNiCuFeO
Authors: Binbin Li , Hui Tan , Ying Han , Wei Tao , Chenglu Lin
Published: March 2011

Polycrystalline MnNiCuFeO was implanted by B+, P+ and Si+ ion beams and thermally annealed. The structure and electrical properties of the sample were measured using SEM, Microprobe (MP), Low Frequency Impedance Analyzer (LFIA) and Spreading Resistance Probe (SRP). The results show that the resistance of grain boundaries is much higher than that of grains. The spreading resistance of the implanted samples is lower by factor of 2 than that of the unimplanted ones. The ratio of the real part Rs (grain effect) to imaginary part Xs (grain boundary effect) decreases with ion beam implantation. From these results, we came to the conclusion that the behavior of the grain boundaries is important to the bulk properties of polycrystalline MnNiCuFeO.
Aluminum Ion Implantation in Silicon Carbide at High Temperature of Target
Authors: Suvorov Alexander V. , Plotkin D. A. , Makarov V. N. , Svetlov V. N.
Published: March 2011

Single crystals and epitaxial films of SiC - 4H and 6H were implanted at an energy of 40 and 90 KeV by ions of Al at various temperatures and high dose.

The implanted layers were studied before and after annealing by Raman scattering, Auger electron spectroscopy and SIMS. Results of this investigation show intensive graphitization of the implanted layer surface, the formation of great associations of defects in the implanted layer and shallow defects. It was found that recrystallization of the implanted layer pushes out a considerable part of aluminum atoms. The nature of the processes in silicon carbide during implantation and annealing is discussed.
High-Tc Superconducting Films Irradiated with Low-Energy Oxygen Ion Beam
Authors: Phedotova V. V. , Zoubetz A. V. , Ges A. P. , Stognij A. I.
Published: March 2011

LPE-grown YBCO single crystal films were irradiated with oxygen ion beam up to a fluence level of 8 × 1019 cm−2 Irradiation parameters were as follows: , beam energy 0.8 keV, current density 0.4 mA/cm2. Ultimate vacuum was not less than 5 × 10−6 Torr, operating vacuum was 2 × 10−4 Torr. Tc = 53K and transition width ΔT> 10 K characterized the starting state of the films. After irradiation Tc was found to increase up to 94 K and Δ to decrease down to 0.5 K. Proceeding from transition character one can conclude that the irradiated film composition was changing into a single phase one. Half widths of the characteristic peaks of x-ray spectra were decreasing with the increase in fluence. The best results were obtained upon the irradiation of cooled samples. Upon heating the samples up to 600° C it was impossible to obtain Tc = 86 k and ΔT = 2 K.
RBS/Channeling Characterization of Ba Implanted Mg
Authors: Da Silva R. C. , Hauser Th. , Melo A. A. , Soares J. C. , Da Silva M. F. , Meyer O.
Published: March 2011

The behaviour of 300 keV Ba ions implanted at room temperature with doses between 1015 and 1017 cm−2 in Mg single crystal and foils was investigated. The results show that the Ba ions do not occupy substitutions sites in Mg, either after the implantation or the annealing treatments. However, pronounced migration of Ba to the surface is observed above 380 °C. The remaining fraction overlaps with the aa-implanted distribution and forms small precipitates. This behaviour is not correlated with the recovery of the Mg lattice which is already complete at about 250 °C. The surface segregation of Ba delays the evaporation of Mg to temperatures near the melting point.
The Effect of Digm and Irradiation-Induced Grain Growth on Interdiffusion in Bilayer Ion-Beam Mixing Experiments
Authors: Alexander Dale E. , Rehn L. E. , Baldo Peter M. , Gao Y.
Published: March 2011

Experiments were performed demonstrating that ion irradiation enhances diffusion-induced grain boundary migration (DIGM) in polycrystalline Au/Cu bilayers. Here, a model is presented relating film-averaged Cu composition in Au with treatment time, grain size and film thickness. Application of this model to the experimental results indicates that irradiation enhances DIGM by increasing the grain boundary velocity. The effects of DIGM and irradiation-induced grain growth on the temperature dependence of ion mixing in bilayers are discussed.
A Universal Criterion for Amortization in Metallic Systems
Authors: Kulp D. T. , Egami T. , Luzzi D. E. , Vitek V.
Published: March 2011

Recent computer simulation studies of electron-bombarded metallic alloys have concentrated on finding a criterion for amorphization. It has been suggested that the thermodynamic properties of volume and total energy can be used as a gauge for defect induced amorphization. Our simulation results indicate that these properties can not be used due to their dependence on processing history. We propose that the distribution of the atomic level shear stresses can be used as this amorphization criterion. Using Finnis-Sinclair type many-body potentials and Lennard-Jones pair potentials, molecular dynamics (MD) simulations on several model systems have been performed. By quantifying the analysis using the average shear stress normalized, by the average shear modulus of the glass, we will present evidence that the crystal becomes amorphous at the defect concentration where the normalized average shear stress reaches a critical value, which is equivalent to the state obtained through quenching from the liquid.
Surface Chemical Routes to Low Contamination Beam Assisted GaAs Etching
Authors: Marshall Duncan , Jackman Richard B.
Published: March 2011

In-situ processing requires totally dry approaches to pattern generation to be developed. Of particular interest are beam driven reactions that can be localised without prior masking. This paper considers the adsorption - desorption characteristics of chlorine, dichloroethane and sulphuryl chloride on GaAs(lOO). The surface reactivity in these systems is seen to vary considerably. The implications of this are considered with regard to their use as chemically assisted ion beam and laser photochemical etching gases.
Dopant and Strain Dependence of Extended Defect Generation in Silicon by 1-MeV Electron Irradiation
Authors: Vanhellemont Jan , Romano-Rodriguez Albert
Published: March 2011

Results are presented of an in-situ study of 1-MeV electron irradiation induced {113}-defect generation in silicon with boron, phosphorus or arsenic doped surface layers. By 1-MeV electron irradiation in a high voltage transmission electron microscope, {113}-defects are dorni-nandy formed in areas with a well defined dopant concentration range which depends on the tjpe of dopant atom, the irradiation temperature and fluence and the sample thickness. The observations for samples with boron and phosphorus concentration profiles are compared with published data on electron irradiation induced ( 113}-defect formation in uniformly doped silicon. In the present paper first results on heavily arsenic doped silicon are presented. It is shown that ihe observed dopant dependence of the {113}-defect generation can be understood on the basis of known point defect reactions. A few irradiation experiments are also performed on a local isolation structure illustrating for the first time the influence of localised tensile and compressive strain fields on {113} -defect nucleation.
Detailed Model for Ion-Beam Induced Adatom Generation
Authors: Breeman M. , Boerma D. O.
Published: March 2011

In earlier low-energy ion scattering experiments of 6 keV Ne ions on Cu(100), Cu adatoms were observed to appear on the surface. The number of produced adatoms per incoming ion was found to decrease to 50% of its initial value of 3.5 after prolonged irradiation. In this paper we present calculations of the adatom production as a function of irradiation dose. From a comparison with the experimental data, the trapping radius of a vacancy was determined to be 5.4 ± 0.9 Å, in agreement with values reported in the literature.
XPS-Analysis of Ion-Beam-Induced Oxidation (IBO) of AlxGa1−xAs Substrates
Authors: Alay Josep-Lluis , Vandervorst Wilfried
Published: March 2011

XPS analysis was used to characterise GaAs, Al0.4Ga0.6As and Al0.8Ga0.2As targets bombarded with an O2+ beam ranging from 1 keV to 5 keV. The bombardments were carried out at different angles of incidence from 0° to 60°. In all cases a strong preferential sputtering of arsenic gives rise to an As-depleted altered layer, formed by a mixture of gallium, arsenic and aluminium oxides with metallic gallium and arsenic. Aluminium and gallium are preferentially oxidized, a fact that correlates with the corresponding heat of formation of the oxides, whereas the arsenic oxidation requires a minimum incorporation of oxygen into the matrix. For all experimental conditions a considerably lower oxidation level has been observed in every case as compared to the IBO of silicon.
The Effect of Structural Relaxation on the Diffusion of Au in Amorphous Pd80Si20
Authors: Wagner A. V. , Spaepen F.
Published: March 2011

The diffusivity of Au in sputter-deposited amorphous Pd80Si20 has been measured by Rutherford backscattering spectrometry (RBS) between 275°C and 380°C. A new method based on scaling of the evolution of the variance of the concentration profile was used to analyze the data. The diffusivity was found to be independent of the Au concentration below 3 at.%. Structural relaxation causes a time dependence that is evident at short times. The kinetics of this relaxation can be described by the bimolecular relaxation model used in the analysis of viscous flow.
Excimer Laser Surface Modification: Process and Properties
Authors: Jervis T. R. , Nastasi M. , Hirvonen J.-P.
Published: March 2011

Surface modification can improve materials for structural, tribological, and corrosion applications. Excimer laser light has been shown to provide a rapid means of modifying surfaces through heat treating, surface zone refining, and mixing. Laser pulses at modest power levels can easily melt the surfaces of many materials. Mixing within the molten layer or with the gas ambient may occur, if thermodynamically allowed, followed by rapid solidification. The high temperatures allow the system to overcome kinetic barriers found in some ion mixing experiments. Alternatively, surface zone refinement may result from repeated melting-solidification cycles.

Ultraviolet laser light couples energy efficiently to the surface of metallic and ceramic materials. The nature of the modification that follows depends on the properties of the surface and substrate materials. Alloying from both gas and pre-deposited layer sources has been observed in metals, semiconductors, and ceramics. Surface enrichment of Cr by zone refinement of stainless steel has also been seen. Rapid solidification after melting often results in the formation of non-equilibrium phases, including amorphous materials. Improved surface properties, including tribology and corrosion resistance, are observed in these materials.
Congruent Melting Temperatures of Si-As Alloys Measured During Pulsed-Laser Melting and Rapid Solidification
Authors: Kittl J. A. , Reitano R. , Aziz M. J. , Brunco D. P. , Thompson M. O.
Published: March 2011

The solidification of Si-As alloys induced by pulsed laser melting was studied at regrowth velocities where the partition coefficient is close to unity. The congruent melting temperatures, TO, of Si-As alloys were determined using a temperature measurement technique developed for this work, and were confirmed with TOmeasurements using three other methods. The time-resolved temperature measurement uses a thin-film platinum thermistor, below and electrically isolated from the Si-As alloy layer, to directly measure the temperature during solidification. This, combined with measurements of transient conductance of the Si-As alloy, time-resolved reflectivity and Rutherford Backscattering Spectrometry, permitted the determination of the solid-liquid interface temperature, velocity and partition coefficient, the latent heat of fusion and TO for Si - 4.5 at. % As and Si - 9 at. % As alloys.
CW Laser-Induced Removal of Interconnections in Submicron Devices
Authors: Auvert Geoffroy
Published: March 2011

The interaction of a cw argon-ion laser with the materials used in the microelectronics technology is described as a pyrolytic effect. A chemical reaction is induced between the oxide layer and the hot irradiated silicon or aluminum line. By making a cross section of the irradiated area using a focused ion beam, the formation of an unstable insulating material covering the conducting material is observed.
Modification of Fused Silica Materials for Excimer Laser Optics—measurement of laser induced defects and its reformation—
Authors: Matsumoto Yasutaka , Yoshikado Yoshihiro , Murahara Masataka
Published: March 2011

Fused silica is widely used material in window and lens applications for excimer laser processing. The transmittance of the laser beam in fused silica is attenuated approximately 40% by high fluence ArF excimer laser irradiation. The attenuation of the transmittance corresponds to the growth of an absorption band at 215nm. This phenomenon is troublesome for laser lithography. To investigate this effect, we examined the laser induced luminescence and absorption under various conditions. The 215nm absorption band was diminished by annealing at 900 °C for 2 hours in He ambient. Ke could successfully obtain good optical material, whose transmittance remains constant with increasing ArF laser(193nm) shot exposure.
Point Defects in GaAs and Other Semiconductors
Authors: Ehrhart P. , Karsten K. , Pillukat A.
Published: March 2011

In order to understand the properties of intrinsic point defects and their interactions at high defect concentrations GaAs wafers were irradiated at 4.5 K with 3 MeV electrons up to a dose of 4.1019 e-/cm2. The irradiated samples were investigated by X-ray Diffraction and optical absorption spectrocopy. The defect production increases linearly with irradiation dose and characteristic differences are observed for the two sublattices. The Ga-Frenkel pairs are strongly correlated and are characterized by much larger lattice relaxations (Vrel=2–3 atomic volumes) as compared to the As-Frenkel pairs (Vrel ≈ 1 at.voL). The dominating annealing stage around 300 K is attributed to the mobility of the Ga interstitial atoms whereas the As-interstitial atoms can recombine with their vacancies only around 500 K. These results are compared to those for InP, ZnSe and Ge. Implications for the understanding of the damage after ion irradiation and implantation are discussed.
Limitations to the Bandgap-Selective Photoelectrochemical Etching of GaAs/AlxGa1−x as Heterostructures
Authors: Khare Reena , Young D. Bruce , Hu Evelyn L.
Published: March 2011

We have used the wet photoelectrochemical (PEC) etch process to demonstrate the selective removal of low aluminum (Al) mole-fraction AlxGa1−xAs layers from those with higher Al mole-fraction. High etch selectivity was found for δx as low as 0.05, but was found to decrease as the incident photon energy approached the energy bandgap of the desired stop-layer. The ultimate selectivity of one layer from an underlying layer was affected not only by differences in material composition, but also by the sequencing of the layers within the structure.
In Situ Studies of Electron Cyclotron Resonance Plasma Etching of Semiconductors by Spectroscopic Ellipsometry
Authors: Nafis S. , Ianno N. J. , Snyder Paul G. , Woollam John A. , Johs Blame
Published: March 2011

In situ ellipsometry at selected wavelengths in the spectral range 280 nm to 1000 nnn was performed during the rf bias assisted electron cyclotron resonance (ECR) etching of bulk silicon, GaAs, InP, and GaAs/AlGaAs/GaAs, and InGaAs/InP layered strcutures by a CCl2F2 based etch gas.

While real time thickness changes for bulk materials cannot be determined ellipsometrically, some insight into the etch mechanism may be gained by observing the effect of the process on the surface dynamically, and after the etch process has been completed. Monitoring of the layered structures during etching can provide a real time measure of the amount of material remaining in the layer being etched, and provide tight process control.
Remote Plasma Cleaning and Ion-Induced Hydrogen Desorption from the Silicon (100) Surface and Its Applications to Si Epitaxy
Authors: Kinosky David S. , Qian R. , Mahajan A. , Thomas S. , Fretwell J. , Munguia P. , Banerjee S. , Tasch A.
Published: March 2011

We have studied the conditions for effective removal of H from the silicon (100) surface by Ar and He plasma bombardment as a function of pressure, plasma power and time. At a given pressure, a range of rf plasma powers exists for effective H-desorption. For example, at 250°C and for 100 mTorr of He, H is desorbed only between 12 and 50W of plasma power. The range of effective powers was found to become narrower with increasing pressure. We have also found the efficacy of the H-plasma clean to be reduced by addition of He and Ar. Substrate damage results from Ar addition and from increased plasma power for pure H. The results are discussed along with Langmuir probe analysis of the various plasma conditions.
Excimer Laser Induced Cryoetching of GaAs and Related Materials
Authors: Freiler Michael B. , Shih Ming Chang , Scarmozzino R. , Osgood R. M. , Tao Ie Wei , Wang Wen I.
Published: March 2011

We report highly resolved, damage-free etching of GaAs and related materials. The etching is activated by excimer laser irradiation at 193 nm of samples maintained at low temperatures (∼140 K) in a chlorine atmosphere (∼5 mTorr). Since the etching is chemical in nature, structural damage to the substrate should not be present. Submicrometer resolution has been achieved by the use of electron beam lithography to pattern a Si3N4 contact mask. We have also successfully used our etching in the fabrication of a single-quantum-well, ridge-waveguide semiconductor laser.
Characterization of Films Made from Silicon Oil Saturated Methane Vapor by Ion Beam
Authors: Lin Sin-Shong , Sloan Janes M.
Published: March 2011

Amorphous carbon films were prepared by the ion beam deposition of methane saturated with silicon pump oil 704. The concentration of Si in the ion deposited coatings could be varied by the temperature of silicon oil bath where saturated vapor was produced. In the process, the vapor ionized at 800 V was accelerated and impinged on glass or stainless steel substrates at ion densities between 0.3–1.5 mA/cm2 for a period of less than 60 minutes. The resulting films were characterized by x-ray photoelectron and Raman spectroscopies. The elemental components of these films include carbon, oxygen and silicon with varying amounts of nitrogen, iron and tungsten contaminations. The microstructure mainly consists of tiny graphitic carbon with sp2 ordered and disordered configurations, numerous carbon-oxygen and carbon-silicon linkages. This simple unique process yields a homogeneous thin coating suitable for many tribological applications.
Stabilization of Metastable Zinc-Blende Phase MnTe by Ionized Cluster Beam Deposition
Authors: Ando K. , Takahashi K. , Takeuchi Y.
Published: March 2011

The ionized cluster beam (ICB) deposition was use to stabilize the metastable zinc-blende (ZB) MnTe films directly on GaAs (100) substrates at 300 °C with MnTe cluster ion beam. Influences of the ionization and the acceleration voltage on film properties were investigated by the reflection high-energy electron diffraction (RHEED), optical reflection, Raman scattering, and photoluminescence. The ZB-MnTe was stabilized by 3kV acceleration of the MnTe cluster beam. These results showed that the ICB deposition is useful to get compounds having crystalline phase different from the structures observed io equilibrium-grown bulk crystals.
An Assessment of ECR Argon Plasma Etching Damage on Si and SiO2 Interfaces
Authors: Nam C. W. , Ashok S. , Tsai W. , Day M. E.
Published: March 2011

Electron cyclotron resonance (ECR) argon plasma has been used (to etch the native oxide on Si and thermal SiO2. The Schottky barrier height modification on both n- and p-Si has been studied as a function of substrate bias and etch time. Deep Level Transient Spectroscopy (DLTS) measurements show clear peaks on both p- and n-Si, but wish low levels of trap concentrations (1012-1013cm−3), and decreasing with depth from the surface. The effects of thermal oxide etching on the Si/SiO2 interface have been estimated with MOS capacitors. Negative flat-voltage shift is observed after argon plasma exposure, which removes the thermal oxide at a rate of over 100 Å/min at 50 V bias. C-V measurements show an order of magnitude increase in interface trap density.
Fabrication and Evaluation of Ternary Co-Fe-Si Structures Produced by Ion Beam Synthesis
Authors: Hunt Tim D. , Sealy Brian J. , Hanebeck Jochen , Reeson Karen J. , Homewood Kevin P. , Gwilliam Russell M. , Meekison C. Douglas , Roger Booker G.
Published: March 2011

Dual implantation of cobalt and iron into silicon (100) wafers and subsequent annealing has been used to form layers containing mixtures of CoSi2 and FeSi2. The structure and properties of the layers were followed by Secondary Ion Mass Spectrometry (SIMS), cross-sectional transmission electron microscopy (XTEM), Transmission Electron Diffraction (TED), Rutherford Backscattering Spectroscopy (RBS), and photoluminescence (PL). When a high dose of both species was implanted, segregation of the cobalt and iron occurred which for 1000°C anneals, resulted in an epitaxial layer of αFeSi2 upon a CoSi2 layer. The epitaxial quality of both of these layers was superior to those previously fabricated by single species implants. For a low dose cobalt implant followed by a high dose iron implant, a single phase solid solution was formed and segregation did not occur. Photoluminescence at 1.54 urn was observed from this layer, but with a much lower intensity and a broader line width than that from a pure βFeSi2 layer.
The Dynamic Compaction of Metallic Powders
Authors: Morris David G.
Published: March 2011

The Dynamic Compaction of powdered materials becomes a particularly attractive technique for consolidating hard materials, because of the ease with which high pressures are achieved, and for metastable materials, because of the possibility of avoiding large-scale, high temperature excursions. The shock-wave conditions necessary for achieving high densities and interparticle bonding are evaluated experimentally. The bonding and melting taking place can be identified by post-consolidation studies, and the inter-relation between compact integrity and melting is shown. An attempt is made to develop a “process window” analogous to that of explosive bonding, to describe the conditions necessary for consolidation. Finally, in view of the necessity for localisation of plastic flow during consolidation, an indication of the influence of material deformation parameters is given.
Effect of Cooling Rate on the Structure of Rapidly Cooled Fe75Si15 B10
Authors: Walter John L. , Berkowitz Ami E.
Published: March 2011

Solidification of metal alloys by rapid quenching can result in the formation of amorphous or microcrystalline solids, or materials with improved microstructural homogeneity, all with the view of forming new phases or obtaining improved properties. Some alloys may be cooled at high rates to achieve “microcrystallinity” but cannot be cooled rapidly enough to become amorphous. Other alloys may achieve both conditions depending on the cooling rate. We have examined the effects of cooling rate on the structure of one alloy that can, depending on the cooling rate, be made partially or completely amorphous. The alloy is Fe75Si15B10 (atom percent) which was formed as ribbon by melt spinning and as powder by spark erosion in dielectrics of different cooling characteristics and by gas-water atomization. The structural characteristics were determined by x-ray diffraction, measurements of magnetic properties and by optical and scanning electron microscopy.
Influence of Short Range Order, Electron Concentration and Size Misfit on the Structure and Thermal Stability of Metallic Glasses
Authors: Bergmann H. W. , Luft U. , Fritsch H. U.
Published: March 2011

The influence of short range order, electron concentration and size misfit on the thermal stability of (Fe100-xMx)83B17 metallic glasses has been investigated (M = Cr, Mn, Co, Ni, Mo, W). The results are discussed together with Curie-temperature measurements and Mößbauer spectroscopy data. The concentration range in which the various stable and metastable phases form is given.
Rapid Solidification Of Composite Materials
Authors: Zielinski Piotr G. , Ast Dieter G.
Published: March 2011

The melt spinning technique was used to prepare composite materials consisting of a metallic glass matrix and a second phase in the form of particles and/or C or SiC fibers. The spatial distribution of the second phase varied with the method used to incorporate the particles into the melt. The observed distributions can be explained by assuming that rotational stirring takes part in the melt puddle. The influence of second phase on the effective quenching rate is discussed and the mechanical properties of Ni75Si8B17 glass containing a variety of second phase particles are reported.
Effect of R-Curve and Inhomogeneities on the Toughness Measurement of Metallic Glasses
Authors: Henning W. , Calvo M. , Osterstock F.
Published: March 2011

Sub-critical crack growth is a function of the degree of relaxation of the amorphous structure and has implications regarding the measurement of annealing embrittlement and the dependence of embrittlement on temperature. The variation of Kc with annealing time is strongly dependent on the size of the initial crack length. Quenched-in inhomogeneities seem to be always present. Their effect depends on the specific testing conditions, especially the testing temperature because the ductile-brittle transition is a function of the degree of relaxation of the amorphous structure. Some doubt is also cast on the accepted assumption that a chevron pattern is representative of plane strain crack propagation conditions.
Ni-Mo-Cr-B Alloys: Corrosion Resistant Amorphous Hardfacing Coatings
Authors: Das S. K. , Norin E. M. , Bye R. L.
Published: March 2011

A series of rapidly solidified Ni-Mo-Cr-B alloys have been investigated for possible application as corrosion resistant hardfacing coatings. As-cast amorphous ribbons were pulverized to powder, which was subsequently applied to a substrate by plasma spraying. The coatings are substantially amorphous, as revealed by x-ray diffraction and transmission electron microscopy. They exhibit ∼95% of theoretical density and exhibit good corrosion and wear resistances, superior to those of many commercially available hardfacing coatings.
Short Range Ordering-Disordering in an FeNiB Metallic Glass
Authors: Kursumovic A.
Published: March 2011

Low temperature relaxation of Fe40Ni40B20 glassy samples was monitored by DSC, velocity of sound and creep recovery measurements. The as-quenched samples exhibited very pronounced exothermic reactions in the temperature region prior to crystallization. Reversible changes were found during subsequent heat treatmentof preannealed glassy material having exothermic and endothermic heat flow during ordering and disordering respectively. Results were found to be in agreement with velocity of sound and creep recovery changes, found earlier , having activation energy for these reversible changes around 160 kJ/mole.
Comparison of Microstructure and Properties Obtained by Different Solidification Techniques
Authors: Bergmann H. W. , Barton G. , Mordike B. L. , Fritsch H. U.
Published: March 2011

The processes responsible for solidification, e.g., nucleation and growth, are influenced to various extents by the currently employed quenching techniques. The microstructures produced by these techniques are discussed and compared.
Crystallization of Amorphous Ni Based Alloys
Authors: Geoffroy G. , Duflos F. , Lasalmonie A.
Published: March 2011

This work presents some results concerning the crystallization of Ni based alloys containing various amounts of boron. We will describe the crystalline phases and show that the nucleation mechanisms can be very different when the boron content is changed.
Microstructures of Rapidly Solidified Aluminum Alloys
Authors: Zindel J.W. , Stanley J.T. , Field R.D. , Fraser H.L.
Published: March 2011

An investigation was performed to study the origin and stability of microstructures in rapidly solidified aluminum alloys. Al-Ni and Al-Fe base alloys were rapidly solidified by means of laser surface melting and melt spinning techniques. Microstructures were studied using optical and transmission electron microscopy. The effect of microstructure on mechanical properties was also studied using microhardness measurements. The origin of the observed microstructural constituents will be explained in terms of features of the metastable phase diagram. The effect of ternary additions on stability will also be considered.
Rapid Solidification Microstructures and Precipitation in AL-Mn Alloys
Authors: Schaefer R. J. , Shechtman D. , Biancaniello F. S.
Published: March 2011

Rapidly solidified Al containing up to to 15 wt.% Mn was prepared by melt spinning. The alloys were examined by TEM and X-ray diffraction in the as-spun condition and after annealing at 450°C. Four precipitate phases were detected, and their growth kinetics were correlated to subgrain structures in the Al matrix.
Rapid Solidification of an Aluminum-Neodymium Alloy
Authors: Savage S. J. , Froes F. H.
Published: March 2011

A rationale for rapid solidification processing of aluminum-lanthanide alloys is given, and preliminary results of microstructural studies on an aluminum-neodymium alloy are presented. Three distinct types of microstructure are seen in the as-cast rapidly solidified material, which are still evident after heat treatment at 350°C for 1 hour. Microhardness measurements indicate each microstructure has a different response to isochronal heat treatments.
Microstructural Analysis of Rapid Solidification and Undercooling in the Al-Ge System
Authors: Kaufman M.J. , Fraser H.L.
Published: March 2011

Submicron powders, amorphous films and melt spun ribbons of various Al-Ge alloys have been analyzed to determine the relative roles of undercooling and cooling rate in the production of non-equilibrium structures. All analyses were performed in transmission electron microscopes equipped with energy dispersive x-ray spectrometers. The submicron powders, produced by electro-hydrodynamic atomization, were analyzed in their as-received condition and then annealed and/or melted using the electron beam as a local heating source. Once molten, the liquid droplets were undercooled at different cooling rates by varying the rate of beam obstruction. In this manner, a number of different microstructures were produced. These included metastable crystalline phases and mixed amorphous/crystalline structures. By combining this technique with a microscope heating stage, it was possible to carry out controlled dynamic undercooling experiments and determine phase selection as a function of undercooling and composition. The amorphous films were rapidly heated with the electron beam in the microscope and metastable as well as stable phases were produced. The results of these complementary analyses will be compared and discussed with reference to current models and theories of rapid solidification.
Microstructures of Rapidly Solidified Titanium-Eutectoid Former Alloys
Authors: Krishnamurthy S. , Vogt R. G. , Eylon D. , Froes F. H.
Published: March 2011

Titanium-base binary alloys containing eutectoid forming additions such as Fe, Si, W, and Cr were rapidly solidified by pendant drop melt extraction, melt spinning, and “hammer and anvil” techniques. The materials obtained were fibers, ribbons, and splats, respectively. The microstructures of these rapidly solidified materials were analyzed by optical microscopy, SEM, and TEM. The fibers showed fine microstructures near the quenched side, but less homogeneous and coarser microstructures were observed away from this side. Similar variations were observed between the edge and the center of splats. The results of this microstructural characterization are discussed, and a comparison made between microstructures obtained by the different rapid solidification methods used.