bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic Roughening in Surface Growth
Authors: Yan Hong , Kessler David A. , Sander Leonard M.
Published: March 2011

In nonequilibrium surface growth processes, such as molecular beam epitaxy and chemical vapor deposition, kinetic roughening plays a significant role in determining surface morphology. The stochastic dynamics in the processes induce novel scaling in surface roughness with respect to growth time and system sizes. We present here a series of numerical simulation studies of simple theoretical models, such as ballistic deposition model and biased solid-on-solid model, to demonstrate the dynamical scaling and phase transitions in a class of surface growth problems in the context of the Kardar-Parisi-Zhang theory. Different dynamical processes, such as desorption and surface diffusion, are shown to have dramatic effects on the scaling and thus the surface structures.
Electronic Structure of Substitutionally Disordered Alloys: Direct Configurational Averaging
Authors: Wolverton C. , Fontaine D. De , Dreysse H. , Ceder G.
Published: March 2011

The method of direct configurational averaging (DCA) has been proposed to study the electronic structure of disordered alloys. Local density of states and band structure energies are obtained by averaging over a small number of configrations within a tight-binding Hamiltonian. Effective cluster interactions, the driving quantities for ordering in solids, are computed for various alloys using a tight-binding form of the linearized muffin-tin orbital method (TB-LMTO). The DCA calculations are used to determine various energetic and thermodynamic quantities for binary and ternary alloys.
A First-Principles Study of the Phase Stability of FCC-Based Ti-Al Alloys
Authors: Asta Mark , Fontaine Didier De , Schilfgaarde Mark Van , Sluiter Marcel , Methfessel Michael
Published: March 2011

In this paper we present results of a first-principles phase stability study of fcc-based Ti-Al alloys. In particular, the full-potential linear muffin tin orbital method has been used to determine heats of formation and other zero-temperature properties of 9 fcc ordered superstructures as well as fcc and hcp Ti, and fcc Al. From these results a set of effective cluster interactions are determined which are used in a cluster variation method calculation of the thermodynamic properties and the composition-temperature phase diagram of fcc-based alloys.
Interatomic Interactions for BCC Metals Based on the Low Order Moments of the Density of States
Authors: Foiles Stephen M.
Published: March 2011

A model of the energetics of bcc transition metals based on the low-order moments of the electronic density of states is presented. The new feature of the model is an additional energy term related to the fourth moment of the density of states. This term reflects the coarse shape of the density of states. The model is tested by the computation of point defect properties, phonon dispersions, structural energy differences and surface properties. The results are compared to experiment, ab-initio calculations and other model interatomic potentials. The results indicate that the inclusion of the fourth moment term in the energy does not significantly improve the description of properties of the bulk bcc metals. However, the fourth moment term substantially improves the description of large deviations from the bcc bulk such as surfaces and alternative crystal structures.
Properties of Complex Materials: A Computer Aided Structural Classification
Authors: Pascale Teresa M. de , Meloni Franco , Serra Marina
Published: March 2011

We discuss the validity of the usually used orbital radii capable to separate differently coordinated compounds in efficient structural maps. In order to account for the real dependence on the angular momentum, we redefine the atomic terms by including the d-states contribution, previously ignored. The choice of the right amount of the correction has been performed thanks to a series of structural maps obtained through a computer-aided code.
Topological Stability of 2-D Vanishing Grains
Authors: Fradkov V. E. , Glicksman M. E. , Nordberg J. , Palmer M. , Rajan K.
Published: March 2011

Grain growth in polycrystals occurs by decreasing the total number of grains as a result of the disappearance of small ones. That is why the both the kinetic and topological details of shrinking of small grains are important.

In 2-D, “uniform boundary model” assumptions imply the von Neumann-Mullins law, and all grains having less than 6 neighbors tend to shrink. The mean topological class ef vanishing grains was found experimentally to be about 4.3. This result suggests that most vanishing grains are either 4- or 5-sided, not transforming to 3-sided ones.

Shrinking of 4- and 5-sided 2-D grains was studied experimentally on transparent, pure SCN, (succinonitrile) polycrystalline films and by direct computer simulation of grain boundary capillary motion together with triple junctions. It was found that the grains which are much smaller than their neighbors are topologically stable.
Molecular Dynamics Modeling of Polymer Flammability
Authors: Nyden Marc R. , Brown James E. , Lomakin S. M.
Published: March 2011

Molecular dynamic simulations were used to identify factors which promote char formation during the thermal degradation of polymers. Computer movies based on these simulations, indicate that cross-linked model polymers tend to undergo further cross-linking when burned, eventually forming a high molecular weight, thermally stable char. This prediction was confirmed by char yield measurements made on γ and e - irradiated polyethylene and chemically cross-linked poly(methyl methacrylate).
Dynamics of Polyatomic Molecules in Porous Silica
Authors: Brodka A. , Zerda T.W.
Published: March 2011

The liquid-solid phase transition of cyclohexane in small pores of sol-gel glass is studied by computer simulation. A cavity model is obtained by placing silica clusters at the corners of a cubic box. A molecule inside the cavity is approximated by an assembly of six Lennard-Jones (LJ) potentials. Translational and rotational motions of C6H12 are studied in the temperature range from 190 K to 333 K. Supercooling is observed and the freezing temperature is depressed in comparison to the bulk phase.
Refractoriness of High-Current and Low Acceleration Voltage Arsenic-Ion Implanted Polycrystalline Silicon Against Fluorine Chemistry
Authors: Saito Yasuyuki
Published: March 2011

The author observed that both high-current-ion-beam and low-accelerationvoltage arsenic-implanted polycrystalline silicon-film surfaces are resistant to radical-fluorine-gas-etching. If we accept the simple assumption that a depth profile of concentration distribution of the implanted high-dose As atoms in polycrystalline Si film can be expressed with a standardized distribution function in the previous report of S. Furukawa, H. matsumura, and H. Ishiwara [Jpn. J. Appl. Phys. 11, 134 (1972)], we can take the premise that the chemical bonding reaction itself between radical-fluorine atoms and silicon atoms is prevented rather than that the covering of an arsenic- metal thin layer like amorphous state prevents the chemical bonding- reaction. We present a model of the prevention Si-F bond formation by high-dose arsenic implantation at low acceleration voltage. The model seems to be related to potential barrier increase and lattice vibration suppression for electromagnetic force-phonon interaction.
Computer Simulations of Cluster-Solid Interactions: Energetic Clusters and Soft Landings
Authors: Ghaly Mai , Averback R. S.
Published: March 2011

The interaction of small energetic clusters of Cu atoms with Cu surfaces has been investigated by molecular dynamics computer simulations. The simulations are fully dynamical and three dimensional; they employ embedded atom method potentials. The simulations described here are an extension of our past work on cluster solid interactions [1]. In this work, the effects of the angle of incidence, energy, size and temperature of the cluster are examined. In addition, soft landings of Cu clusters on Cu are simulated.
Raman Spectroscopy Analysis of Nitrogen Ion Implantation in Silicon and Correlation with Transmission Electron Microscopy
Authors: PéRez-Rodríguez A. , Romano-Rodríguez A. , Morante J. R. , Esteve J. , Montserrat J.
Published: March 2011

In this work Si samples implanted with nitrogen (N+ or N2+) at a dose of 1017 cm−2 are characterized by Raman spectroscopy and cross section transmission electron microscopy (XTEM). The correlation between the Raman spectra obtained with different excitation wavelengths and XTEM observations allows to determine the structural features related to the layers contributing to the total spectra. The evolution of these features with the annealing treatments (up to 1150°C) is studied. The results obtained show, after the annealing treatment at the highest temperature, the presence of silicon nitride precipitates in the silicon subsurface region, and the formation of a nitrogen rich polycrystalline Si layer with Si3N4 grains. The Raman spectra from the subsurface region show a remaining shift of -0.15 cm−1 when compared to the spectra from unimplanted Si. This shift, together with the similar shape of both Raman lines, suggests the presence in this region of an average tensile stress of 37.5 MPa.
Ultra-Shallow P+/N Junctions Formed by SiF4 Preamorphization and BF3 Implantation Using Plasma Immersion Ion Implantation
Authors: Jones Erin C. , Im Seongil , Cheung Nathan W.
Published: March 2011

Sub-100 nm P+/N junctions are fabricated by implanting wafers in the plasma immersion ion implantation system (PIII). Ions from SiF4 and BF3 plasmas are implanted at energies from 4–6 keV and 2 keV, respectively. The amorphous region formed by SiF4 im-plantion is shown to be effective in slowing B diffusion during a 10 sec, 1060°C rapid thermal anneal step. Channeling and transmission electron microscopy studies show the recrys-tallized amorphous region is comparable in quality to an unprocessed Si wafer, and the implantation and annealing sequence has no detrimental effects on the physical or electrical characteristics of fabricated devices. Diodes have forward ideality factors of 1.05 to 1.06 and reverse leakage as low as 2 nA/cm2 in the diode bulk at -5 V applied bias.
Retardation and Enhancement in Lateral Solid Phase Epitaxy of Si on SiO2 by MeV Electron Beam Irradiation
Authors: Saito S. , Okabayashi H. , Mori H. , Komatsu M.
Published: March 2011

We have demonstrated the high energy (MeV) electron beam irradiation effects on lateral solid phase epitaxy (L-SPE) of Si-on-insulator (SOI). Thinned samples were set on a hot stage in a 2 MeV electron microscope and L-SPE growth under 2 MeV electron irradiation conditions was monitored in-situ by using the same microscope. L-SPE growth rate for the irradiation dose of 1021 cm−2 was enhanced by about 1.5 times greater than that under unirradiated condition. For electron beam irradiation doses higher than about 1023 cm−2, L-SPE growth was suppressed. Displacement of Si atoms, contamination effect and ionization effect are discussed as causes for the growth rate retardation and enhancement of L-SPE by electron beam irradiation.
Computer Simulation of Heat Flow Induced by Laser Irradiation in Presence of Heat Sinks or Sources
Authors: Tosto Sebastiano
Published: March 2011

The paper concerns the computer simulation of heat flow induced on matter by laser irradiation in presence of heat sources or sinks. The model is 3D analytical and accounts for the dependence of thermal properties of matter on temperature. The results describe in particular the effect of a heat source due to a local phase change or solid state reaction releasing energy in a point of the laser affected zone. The purpose of the paper is to evidence how this additional energy affects the thermal field and then the heating and cooling rates. PACS 47.25.-Qv
A Mössbauer Study on Solid Krypton Precipitates in Aluminium and Silicon
Authors: Greuter M. J. W. , Niesen L. , Van Veen A.
Published: March 2011

Mössbauer spectroscopy on the 9.4 keV transition in 83Kr is used to study inert gases in metals and semiconductors. An absorber was made by implanting 83Kr at 110 keV in Al foils to a total dose of 1.7· 1016 Kr cm−2, leading to the formation of small precipitates (bubbles). Spectra on the as-implanted sample were taken as a function of temperature for three 83RbI sources which differ in line shape due to a different water content. A model is presented to extract the absorber parameters from the spectra in a consistent way, in spite of the different sources used. The spectra of Kr bubbles in Al produced by high dose implantation show two components: a single line from Kr inside the bubble and a quadrupole split component from Kr at the Kr-Al interface. The total absorption area could be fitted very well assuming a simple Debye model, yielding a Debye temperature of ΘDT = 101(2) K. For the individual components we obtained Debye temperatures of ΘDQ = 98(6) K and ΘDS = 90(10) K. The isomer shift of the bulk fraction is significantly larger than that of a solid Kr layer at ambient pressure, reflecting the fact that the s-density increases under compression. The size of the precipitates can be estimated to be 1.5–1.8 nm. Thin KrSi films, produced by Kr plasma sputter deposition, were characterized using cross-sectional X-ray analysis. The results clearly show two different layers. Presumably, the film grows at first as c-Si with a low Kr concentration, but after having reached a certain critical thickness, further growth proceeds as a-Si with a high Kr concentration. For Mössbauer spectroscopy an absorber of 83KrSi was made by plasma deposition on an Al foil. The spectra can be fitted with a single line and a quadrupole component, both with isomer shifts much larger than found in the case of small Kr bubbles in Al. No change in the total absorbed area was observed from 4.2 to 200 K indicating a lower limit of 250 k for the Debye temperature. Both observations indicate that the Kr resides in very small clusters.
Cross-Sectional TEM Studies of DIGM in Irradiated Au-Cu Bilayers
Authors: Gao Yuzun , Alexander Dale E. , Rehn L. E.
Published: March 2011

Cross-sectional transmission electron microscopy was used to study diffusion-induced grain boundary migration (DIGM) in irradiated and annealed Au/Cu bilayers. Using this technique, in combination with small probe X-ray energy dispersive spectroscopy, DIGM alloyed zones in Au were identified in an irradiated sample.
HREM of Electron Irradiated Quartz
Authors: Qin L. C. , Hobbs L. W.
Published: March 2011

In situ electron irradiation has been carried out in transmission electron microscopes to monitor the dynamic evolution of α-quartz during the transition to the metamict state from the crystalline state. Crystals of different orientations were examined. HREM images were digitized and Fourier transformed to monitor degradation of periodicities. The final uniform metamict structure was characterized by radial distribution functions obtained from energy-filtered electron diffraction.
A Vibrational Analysis of Au Implanted Al2O3 Single Crystals: Ion and Thermal Annealing Effects
Authors: Henderson D. O. , Morgan S. H. , Mu R. , Chen N. , Magruder R. H. , White C. W. , Zuhr R. A.
Published: March 2011

The implantation of Au into Al2O3 leads to disruption of the crystal order producing an amorphous layer. Annealing the implanted crystals at 1373 K restores the crystallinity and also imparts a purple color to the implanted layer which is attributed to a surface plasmon resulting from the formation of Au colloids.
Investigation of Ion Beam Mixing of Iron Marker Layers in Aluminum Oxide by RBS
Authors: Cooper Elizabeth A. , Nastasi Michael , Sickafus Kurt E.
Published: March 2011

Thin films made with a thin embedded marker layer of iron or iron oxide in amorphous alumina were ion mixed with 210 keV Ar over a temperature range of RT to 750°C in vacuum. The dose range was 5×l015-7×l016ions/cm2with an average dose rate of 4.5×1012ions/cm2-sec. The resulting marker distributions were analyzed using RBS. Spreading of the iron RBS peak due to mixing into the alumina matrix was observed in the Fe2O3marker samples and was clearly seen to be a function of temperature (>400°C) and dose, whereas for the Fe marker sample, no such temperature dependence was observed. An activation energy for the thermally assisted ion mixing in the Fe2O3marker sample was determined to be 0.69 eV in comparison to an activation energy of 1.77 eV for samples that underwent only a thermal treatment.
Ion-Beam Amortization of Ca2La2(SiO4)6O2 Single Crystals
Authors: Weber William J. , Wang Lu-Min
Published: March 2011

Single crystals of Ca2La8(SiO4)6O2 were irradiated with 1.5 MeV Xe+, 1.5 MeV Kr+, 1.0 MeV Ar+ and 0.8 MeV Ne+ ions to investigate the effects of recoil-energy spectrum, temperature, and crystallographic orientation on irradiation-induced amorphization. The irradiations were carried out using the HVEM-Tandem Facility at Argonne National Laboratory. The structural changes and the ion fluence for complete amorphization in the electron transparent thickness of the specimens were determined by in situ transmission electron microscopy. The displacement dose determined for complete amorphization was approximately 0.6 dpa for the Xe+, Kr+, and Ar+ ion irradiations but increased to 1.4 dpa for the Ne+ ion irradiations, which may reflect an effect of lower recoil energies. The ion fluence for complete amorphization increased exponentially with temperature over the range from 25 to 400°C. Amorphization was not observed at 500°C. The activation energy associated with this simultaneous annealing process was estimated to be 0.13 eV, and the critical amorphization temperature was estimated to be 438°C for the 1.5 MeV Kr+ irradiations.
Temperature Dependence of the Kinetics of Silicon Amorphization by He Ion Implantation
Authors: Laânab L. , Roumili A. , Faye M. M. , Gessinn N. , Claverie A.
Published: March 2011

We have studied by XTEM the kinetics of Si amorphization by light ion implantation (He) as a function of substrate temperature. The analysis of these kinetics has been performed within the framework of the “Critical Damage Energy Density” model which is shown to apply for temperatures up to 250 K. There is a drastic change in the efficiency of the amorphization process at about 175 K. These results are discussed and explained by considering the different types of defects (I, V, I2, V2, complexes…) that can be stabilized in c-Si depending on the temperature. Above 150 K, the amorphization proceeds through the accumulation of interstitials and vacancies while at higher temperature it proceeds through the accumulation of di-interstitials and di-vacancies left in the network after annihilation and recombination of the Frenkel pairs created by the bombardment.
Crystallization of Tin-Implanted Amorphous Silicon Thin Films
Authors: Lin Fuyu , Hatalis Miltiadis K.
Published: March 2011

The crystallization of Sn-implanted amorphous silicon was studied as a function of tin implant dose and annealing conditions by transmission electron microscopy. The films were implanted at an energy of 110 keV with a dose in the range of 5 × 1014 to 5×1016 cm−2 and were annealed at a temperature in the range of 450°C to 550°C. An enhanced rate of crystallization in amorphous Si-Sn films compared to the non-implanted amorphous silicon films during thermal annealing was observed. The crystallization process of Si films implanted with tin at a dose of 2.5×1016 cm−2 or less is very similar to unimplanted silicon films except higher nucleation rates and shorter crystallization time were observed with increasing tin dose. Films implanted with tin at a dose of 2.5×1016 cm−2 or more display extremely rapid crystallization (3 hours at 450°C) and very fine grain structure (10 nm); no substantial grain growth has been observed during lurther annealing, but some single crystal-like areas were formed. In-situ annealing of silicon implanted to 5×1016 cm−2 showed that the crystallization process is enhanced by the formation of the liquid tin phase.
Roughness Effects During Focused Ion Beam Repair of X-Ray Masks with Polycrystalline Tungsten Absorbers
Authors: Kola R. R. , Celler G. K. , Harriott L R.
Published: March 2011

Tungsten is emerging as the absorber material of choice for x-ray masks due to recent advances in the deposition of low stress films. For a practical technology, the masks must be free from defects. These defects may be in the form of excess or missing absorber. Finely focused ion beams have been used for defect repair on x-ray masks, both for removal of excess absorber material by physical sputtering and for addition of absorber material by ion-induced deposition. The eifect of ion channeling in polycrystalline tungsten films is spatially nonuniform material removal during sputtering. Different grains will have significantly different sputtering yields, depending on their orientation with respect to the direction of the ion beam. The repaired features then suffer from roughness on the bottoms and sidewalls of the sputter craters. We have investigated the use of XeF2 assisted sputtering with a 20 keV Ga+ focused ion beam to reduce this roughness. The chemical etching component of the material removal lessens the directional dependence and therefore the roughness during defect repair. It was also found that chromium etch rate was reduced in the presence of XeF2 gas while the etch rate of W was enhanced so that the removal rate of Cr is much less than that of W. We can take advantage of this etch selectivity by using a thin Cr layer under the W absorber as an etch stop layer to eliminate the roughness at the bottom of the features and a thin layer of Cr on top of the W as an etch mask for reducing the sidewall roughness.
Solute Trapping in Metals
Authors: Smith Patrick M. , Reitanot Riccardo , Aziz Michael J.
Published: March 2011

Many of the advances in rapid solidification processing of metallic alloys exploit the trapping of solute which occurs at high solidification velocities. The difficulty of performing experiments which measure such high solidification velocities in metals has until now prevented accurate measurements of solute trapping in these systems. We have observed the transition from near-equilibrium solute partitioning to solute trapping during solidification at m/s velocities in aluminum alloys, and have compared the predictions of various solute trapping models. Aluminum thin films deposited on insulators were ion-implanted with Sn, Cu, Ge, and In, and were pulsed-laser melted; plane-front solidification was achieved, and regrowth velocities of 0.6 m/s to 5 m/s were measured with the transient conductance technique. Of the existing solute trapping models, the Continuous Growth Model of Aziz was found to fit the observed dependence of the partition coefficient on solidification velocity more closely than any other single-parameter model. The diffusive speed, which locates the transition from solute partitioning to solute trapping, was found to vary from 6 m/s to 38 m/s for various solutes in aluminum. We have examined correlations between the diffusive speed in the Continuous Growth Model and known alloy properties in order to allow better estimates of the diffusive speed to be made for alloy systems in which it has not been measured; the relation between the diffusive speed and the equilibrium partition coefficient will be discussed.
The Effect of CU Intermediate Layer made by IBAD on the CU Surface Film of E–Gun Evaporation
Authors: Yang Jie , Wang Chen , Tao Kun , Fan Yudien
Published: March 2011

Cu intermediate layers (IL) by argon ion beam assisted deposition(IBAD) between substrates and Cu surface films (SF) deposited by electron-gun were made and their effect on the microstructure and properties of the Cu surface films were studied. Primary deposition variables were ion energy and substrates type. Trends in crystallographic texture, crystal-size and resistivity of Cu surface films with different IBAD layers on different substrates are significantly different. Analyzed by RBS, and XRD, the IBAD intermediate layer changed the crystallinity of Cu SF and increased the interface adhesion between the Cu SF and substrate. The experimental results shows that films with lower resistivity and better interface adhesion could be obtained by IBAD- PVD combined technique. The mechanism of crystallographic texture formation is also discussed.
Study of Oxygen-Ion-Beam-Assisted Evaporated Aluminum Oxide Films
Authors: Franzen W. , Tetreault T. , Kosik W. , Croft W. , Hirvonen J. K.
Published: March 2011

Aluminum oxide films have been deposited by electron-beam evaporation on heated substrates under oxygen ion bombardment. Substrates were crystalline silicon, grafoil and glass. Both substrat temperature and ion current density were changed for each deposition The films deposited on silicon were examined by spectroscopie ellipsometry which showed that for substrate temperatures between 70°C and 250°C the index of refraction, and therefore the film density, first rose and then decreased with increasing ion current density. Ai 400°C the index reached a plateau under these conditions. Study by Rutherford backscattering of films deposited on grafoil showed no significant correlation between oxygen-aluminum stoichiometry and fi; density, suggesting that the decrease in density for large ion currei is not due to oxygen-ion incorporation, as has been suggested in the past. The films deposited on glass at 400°C showed some evidence of crystallization.
Formation of buried α- and β- FeSi2 in (100) Si by high dose ion implantation
Authors: Maex K. , Lauwers A. , Van Hove M. , Vandervorst W. , Van Rossum M.
Published: March 2011

A study on ion beam synthesis of buried α- and β-FeSi2 in >100< Si is presented. Phase formation has been investigated as a function of implant and anneal temperature. Layer characterization was performed by RBS, XRD, resistivity, spreading resistance and Hall effect measurements. Orientation effects in the layers have been observed depending on the implant temperature. Transport measurements show that die holes are the majority carriers in the semiconducting layers.
Ion Beam Synthesis of Buried CoSi2 Layers in SiGe Alloys
Authors: Jebasinski R. , Mantl S. , Dieker Chr. , Dederichs H. , Vescan L. , Butz R.
Published: March 2011

Synthesis of buried, epitaxial CoSi2 layers in Si1−xGex alloys (x =0.48 and x = 0.09) by 100 and 150 keV Co+ ion implantation and subsequent rapid thermal annealing was studied by X-Ray diffraction, Rutherford backscattering spectroscopy, He ion channeling, Auger Eectron Spectroscopy and Transmission Electron Microscopy. Buried single-crystal CoSi2 layers in the Si0.91Ge0.09 alloy containing ≈ 1 at% Ge were formed. The suicide formation causes an outdiffusion of Ge leading to an increase in the Ge concentration of the adjacent SiGe layers. In contrast, in the Si0.52Ge0.48 alloy no buried suicide layers could be produced.
Correlation of Optical Properties and Structural Analysis for Cobalt Silicide Layers Buried in Silicon
Authors: Perry C. H. , Lu F. , Namavar F. , Maruska H. P.
Published: March 2011

The optical reflectivity from buried and exposed CoSi2 layers produced by Co ion implantation of Si substrates has been measured over the energy range 0.012–6.2 eV (0.2- 100 μm). Both unannealed and annealed layers were investigated. The complex dielectric constant of the bare CoSi2 layer was obtained from a Kramers-Kronig analysis. The plasma frequency, carrier concentration and relaxation time of the buried CoSi2 layers were obtained from classical dispersion analyses of the multicomponent reflectivity data. The effective carrier concentration derived from the optical data and the measured chaneling from Rutherford back scattering correlated with anneal temperature.
The Structure of Rapidly Solidified Powders of Ni3Al and Ni3 Al + B + Ti
Authors: Baker I. , Ichishita F. , Schulson E.M.
Published: March 2011

Powders of stoichiometric Ni3Al and Ni3Al containing boron and titanium were produced by rapid solidification rate (RSR) processing. Most particles were found to be spherical; some had skins and some contained holes. Fractured particles were found, indicating possible brittleness. Particle size distributions were log-normal with an arithmetic mean particle size of 23.5μm. Both alloys exhibited a dendritic structure in which compositional differences were present. In addition, stoichiometric Ni3Al contained interdendritic lamellae. X-ray diffractometry indicated that the powders were only partially ordered.
High Strength Nickel-Chromium-Molybdenum Microcrystalline Alloy Via Rapid Solidification Technology (Rst)
Authors: Panchanathan V.
Published: March 2011

There is a growing national need for development of new improved materials having superior corrosion resistance combined with high mechanical strength. This paper discusses the properties and corrosion behavior of a new nickel-chromium-molybdenum microcrystalline alloy made via rapid solidification powder process, making it suitable for potential applications in corrosive environments. The alloy, called Markomet 1119, has the following composition in weight percent:

Bal Ni, 20.3Cr, 22.8Mo, 2.9Fe, 0.5B, 0.8C.

This is prepared as rapidly solidified powder by the method of a melt-spinning-pulverization process. The powder is consoldated into rods by hot extrusion. The mechanical properties and corrosion tests carried out on Markomet 1119 are reported. The microstructural feature of the alloy as investigated by SEM is also reported.
Metallic Glasses and Metastable Crystalline Phases Produced by Picosecond Pulsed Laser Quenching
Authors: Lin C.-J. , Spaepen F.
Published: March 2011

The mechanism of ultrafast cooling (1012K sec−1) by picosecond pulsed laser irradiation is reviewed, and it is demonstrated that only partitionless transformations can occur. The glass formation range in a number of binary systems is reviewed, demonstrating that many glasses can be formed below the To-line. The formation of metastable crystalline alloys in the Fe-B, Ni-Nb, Cu-Co and Au-Co systems is reported.
Growth and Surface Morphology of Thin Silicon Films Using an Atomic Force Microscope
Authors: Hegde Rama I. , Chonko Mark A. , Tobin Philip J.
Published: March 2011

The growth and surface morphology of thin LPCVD silicon films were investigated with an atomic force microscope (AFM). Silicon films of 30 nm thicknesses were deposited on SiO2 using SiH4 at four different temperatures between 550 °C and 625 °C. These AFM results permitted visualization of silicon surface granularity, roughness, and the transition with temperature from amorphous to crystalline structure between 550 °C and 580 °C. The surface of the amorphous film deposited at 550 °C is very smooth and the film is continuous physically, while the film formed at 580 °C appears crystalline, rough and porous. At 600 °C and 625 °C the films are fully crystalline. For these higher temperature films surface roughness and the average grain size decreased significantly compared to 580 °C film. Crystallinity and film continuity were further examined by x-ray diffraction (XRD) and cross-sectional TEM measurements.
Adatom Concentration Profiles on Simulated Vicinal Surfaces During Epitaxial Growth
Authors: Shitara Tomoya , Suzuki Takashi , Vvedensky Dimitri D. , Nishinaga Tatau
Published: March 2011

Concentration profiles of surface atoms have been obtained from Monte Carlo simulations of epitaxial growth with anisotropic nearest-neighbor bonding on two different vicinal GaAs(001) surfaces which are misoriented toward [110] (denoted asA) and [110] (denoted asB). These profiles are compared with predictions based upon the original Burton-Cabrera-Frank (BCF) theory and with a modified BCF theory which accounts for the fact that all atoms, not simply free adatoms, can participate in surface diffusion. On both surfaces the modified BCF equation provides a more accurate description of the adatom concentration profiles than that obtained using only the free adatom concentration. This is due to step detachment processes which leads to an effective source of free adatoms that is not taken into account in the original BCF approach. Above the temperature where the growth becomes dominated by step advancement, the curvature of the concentration profile of potentially active atoms on both surfaces are similar but the concentrations differ due to the difference of the capture efficiency of the two types of step edges.
Correlation Length Scaling During the Early Stages of Epitaxial Growth
Authors: Haider Niaz , Wilby Mark R. , Vvedensky Dimitri D.
Published: March 2011

We have calculated the height-height correlation function by means of Monte Carlo simulations of a solid-on-solid model. These simulations reveal that the position and sizes of the islands formed during the first half-monolayer are highly correlated, a feature which has also been noted in recent x-ray studies of growth by OMCVD. This morphology results in the emergence of a characteristic length,ℓ, in the correlation function, which is found to obey the scaling lawℓ = (D)/J)γ, whereDis the diffusion length, andJis the deposition flux. The value of the exponent γ varies with coverage and depends on the growth conditions.
The Characteristics of LPCVD Aluminum Films: Nucleation and Selectivity
Authors: Lee K.-I. , Kim Y.-S. , Joo S.-K.
Published: March 2011

Growth kinetics of CVD Al films using TIBA(Tri-IsoButyl-Aluminum) as a source material were investigated. Nucleation activation energy of aluminum on the silicon substrate was determined to be 3.2 eV for the first time in this work. It turned out that selectivity between Si and SiO2 was very sensitive to the substrate temperature during deposition, which could be well explained from the nucleation activation energy derived in this work. It was found that the surface topology of aluminum films could be improved by reduction of nucleation activation energy through pre-treatment of the substrate.
Distinguishing Between Coherent Interdiffusion and Incoherent Roughness in Synthetic Multilayers Using X-Ray Diffraction
Authors: Xu Z. , Tang Z. , Kevan S. D. , Novet Thomas , Johnson David C.
Published: March 2011

ABSTRACT:: We have developed a method to separate coherent interfacial interdiffusion from incoherent interfacial roughness by extending an electromagnetic dynamical theory to calculate the reflectivity of a multilayer having an arbitrary interfacial profile with a variable degree of randomness in the repeating layer thicknesses. We find that the intensity of the subsidiary maxima are extremely sensitive to incoherent roughness while the intensity of the Bragg maxima are largely determined by the interfacial electron density profiles. Experimental data are modeled in a manner similar to that used by Warren and Averback to determine domain size of crystallites. We divide the multilayer into coherent domains differing from one another by small deviations from the average layer thicknesses. The diffraction intensity from each of these domains is then added to obtain the experimental pattern. The diffraction spectra of a set of Pt/Co multilayers with similar layer thicknesses but prepared with different sputtering gases illustrates the ability to separate the effects of coherent interdiffusion from incoherent roughness. The extent of incoherent roughness obtained using this model to analyze the diffraction data of these Pt-Co multilayers is in good agreement with TEM and STM results from the same samples. The diffraction patterns could not be simulated with abrupt concentration profiles and the extent of interdiffusion was found to be correlated with the energy of reflected neutrals present during the synthesis of the multilayers.
Growth Kinetics of Molecular Beam Epitaxy on Non-Singular Surfaces
Authors: Egler J. F. , Otsuka N. , Mahalingam K.
Published: March 2011

Growth kinetics on non-singular surfaces were studied by Monte Carlo simulations. In contrast to the growth on singular and vicinal surfaces, the sticking coefficient on the non-singular surfaces was found to decrease with increase of the surface roughness. Simulations of annealing processes showed that surface diffusion of atoms leads to a stationary surface roughness, which is explained by multiple configurations having the lowest energy in the non-singular surface.
A Study of MOCVD-Grown Gallium Nitride Nucleation Layers on Sapphire
Authors: Estes Wickenden A. , Wickenden D. K. , Kistenmacher T. J. , Ecelberger S. A. , Poehler T. O.
Published: March 2011

Nucleation layers of GaN have been deposited in an MOCVD reactor on (0001) sapphire, over a range of temperatures and layer thicknesses, using either N2 or H2 carrier gas. The layers have been found to be continuous, textured films as deposited at low temperatures (600°C), but to reorder upon annealing, segregating into nucleation sites which exhibit the normal heteroepitaxial relationship with the sapphire substrate.
Direct Observation of a Surface Phase Transition by hot Tunneling Microscopy
Authors: Hwang Ing-Shouh , Golovchenko Jene A.
Published: March 2011

We study a reversible phase transition of one monolayer of Pb on a Ge(l11) surface over a range of temperature from below to above the transition temperature (∼175°C) with the tunneling microscope. The high temperature l×1 phase is a ordered monolayer l×l 2D solid. Below the transition temperature, Pb atoms are displaced from their ideal T1 positions to form trimers with periodicity.
Defect Characterization of InAs Films Grown by Two-Step MOCVD on (100) InP Substrates
Authors: Ballal A. K. , Salamanca-Riba L. , Partin D. L.
Published: March 2011

In this paper we investigate the defect morphology and misfit strain in InAs films grown on (100) InP substrates using two-step metal organic chemical vapor deposition (MOCVD). High quality InAs films were obtained despite the 3.2% lattice-mismatch between the InAs film and the InP substrate. Cross-sectional and plan-view transmission electron microscopy has been used to characterize the ∼3μm thick InAs films. Almost all the lattice mismatch is accomodated by an orthogonal array of pure edge Lomer dislocations which are favored over the 60° type since they are more efficient in relieving misfit strain. In addition to misfit dislocations, threading dislocations were observed propagating through the film. Most of the threading dislocations were 60° type dislocations along the < 211 > and < 110 > directions on inclined {111} planes. The threading dislocations originate from island coalescence during film growth. High resolution electron microscopy shows the epitaxial relationship between the film and the substrate and reveals an abrupt and sharp interface with periodic dislocation cores.
A Model for Lattice-Mismatched Epitaxy: A Continuum View
Authors: Orr B. G. , Snyder C. W.
Published: March 2011

To date, primarily only idealized equilibrium models for the growth mode and strain relaxation of elastically strained overlayers have been proposed. Here we present a general continuum model for lattice-mismatched epitaxy. As molecular beam epitaxy is inherently a nonequilibrium growth process, surface diffusion kinetics is incorporated in the model. Additionally, a new strain relaxation mechanism in a dislocation-free film is considered. Experimental support for our view is obtained from measurements made by reflection high energy electron diffraction, scanning tunneling microscopy, and transmission electron microscopy on the growth of InGaAs on GaAs(100). These results demonstrate the strong effects which strain, surface diffusion kinetics, and surface energy have on growth mode. From analytical and numerical analysis in 1 + 1 dimensions, the interrelationship of such physical factors is revealed. Our improved understanding enables control over the growth behavior of strained-layer superlattices and heterostructures.
Novel Glide Planes in Epitaxially Grown Semiconductors
Authors: Albrecht M. , Strunk H. P. , Hansson P. O. , Bauser E.
Published: March 2011

The accommodation of misfit stresses during heteroepitaxial growth of Ge0.85Si0.15 on Si(110) from In solution is studied by transmission electron microscopy. The regular misfit dislocation network forms at the interface and can be explained by glide of dislocations in a secondary a/2<110>{311} glide system. The occurrence of this secondary glide system is analyzed in terms of a mechanical equilibrium analysis that includes a frictional force due to a static Peierls barrier.
Internal Stresses and Damping in Ni/Cu Multilayered Thin Films
Authors: Su C. M. , Oberle R. R. , Cammarata R. C. , Wuttig Manfred
Published: March 2011

The internal stresses and anelastic properties of an electrodeposited Ni/Cu multilayered membrane as measured dynamically using a vibrating membrane method are reported. Our results indicate that the as-deposited membrane has a high internal stress approaching the yield strength. Due to the accuracy of the experimental method, the damping of the multilayered membrane can be measured in the presence of the high internal stresses. It is shown that the relatively large damping capacity exhibited by the multilayered film is different from classical damping associated with the modulus defect, and may be related to an interfacial relaxation effect such as sliding.
Analysis of the Enhanced Growth Rate of Silicon-Oxide Layers in the Thin Regime by Incremental Growth
Authors: Ajuria Sergio A. , Kenkare Prashant U. , Nghiem Anh
Published: March 2011

Silicon oxidation kinetics in the thin regime are studied by a unique method in which thermally grown as well as densified CVD-deposited oxides are incrementally reoxidized and measured. Strikingly higher oxidation rates are obtained through deposited oxides, as compared to thermal oxides, suggesting that oxidations are suppressed after an initial layer is grown rather than enhanced during initial layer formation. We show that these findings tend to support initial oxidation models based on stress.
Microstructural Evolution of Multilayered Oxide Scales on Stainless Steels
Authors: Basu S. N. , Nath D. , Tebbets J.
Published: March 2011

Si containing stainless steels form complex oxide scales during high temperature oxidation at 900°C. These scales consist of an outer iron chromium manganese spinel layer, an intermediate Cr2O3 (chromia) layer and an inner SiO2 (silica) layer. During isothermal oxidation, alloys exhibit minimum weight gain when the inner silica layer is continuous, due to its effectiveness as a diffusion barrier. This continuous silica scale can be formed in a short time only by a combination of fine alloy grain size and high silicon content. However, formation of a continuous silica layer may lead to scale spallation on cooling, thus having a deleterious effect on the oxidation resistance of the alloy.
Metastable Sic and SiGeC Alloys by Carbon Implantation and Solid Phase Epitaxy
Authors: Strane J. W. , Edwards W. J. , Mayer J. W. , Stain H. S. , Lee B. R. , Doyle B. L. , Piorauz B. T.
Published: March 2011

We demonstrate the formation of metastable Si1-yCy and Si1-y-xGexCy alloys by C ion implantation and solid phase epitaxial regrowth. Carbon was introduced into Si and SiGe layers by 5, 12 and 25 keV implants to achieve nearly uniform profiles of 0.7 and 1.4 at.% C. The 0.7 at.% C specimens exhibit the highest quality epitaxial layers after SPE regrowth, whereas in higher C concentration specimens solid phase regrowth was impeded. The localized vibrational mode of C occupying substitutional lattice sites in the diamond lattice provides a signature of the metastable phase and is used to monitor the loss of stability due to precipitation of silicon carbide. The Sic and SiGeC alloys retained substitutional carbon during 30 minute isochronal anneals up to 850°C.
The Determination of Step Heights on the Non-Uhv Heat-Treated MgO (100) Surface by CBED
Authors: King Simon , McKernan Stuart , Barry Carter C.
Published: March 2011

Conditions are established whereby step heights may be measured in the acid-washed and air-annealed MgO single-crystals currently employed as substrates for pulsed-laser-deposition. Preliminary data indicates that the steps are typically a few nanometers in height.
Time-Resolved Optical Studies of Amorphous CoSi Thin-Film Crystallization
Authors: Libera M. , Kim T. , Siangchaew K. , Clevenger L. , Hong Q.
Published: March 2011

Time-resolved reflection and transmission measurements during heating are coupled with transmission electron microscopy (TEM) to study the crystallization of amorphous 75nm Co49Si51 films. The reflection decreases and the transmission increases upon crystallization. Optical data are converted to a measure of the fraction crystallized, χ=χ(T,t). A Kissinger analysis gives an activation energy for crystallization of 1.1 eV. TEM analysis of films crystallized in-situ show they are principally CoSi2 with a small amount of CoSi2. These results are being used for kinetic modelling of crystallization of amorphous Co-silicide films for potential use in Si mosfet and bipolar technologies.
A Model for Double Positioning Twin Formation in Cubic SiC on Noncubic SiC Substrates
Authors: Yoo Woo Sik , Beetz. Charles P. , Chien Fen-Ren , Nutt Steven R. , Kimoto Tsunenobu , Matsunami Hiroyuki
Published: March 2011

As an attempt to explain polytype formation and crystal growth of SiC we propose an electrostatic model in which electrostatic Coulomb force is considered as an interatomic force. The dependence of surface potential on the stacking sequence of atoms in substrates was investigated, and the growth simulation was tried considering the energetic balance under various interaction lengths.The model predicts the double positioning twin formation and the difference in area between twins in cubic 3C-SiC growth on hexagonal 6H-SiC and rhombohedral 15R-SiC substrates. The prediction was experimentally tested by simultaneous chemical vapor deposition growth on basal planes of 6H-SiC(0001) and 15R-SiC(0001). Polytype and interface structure of both specimens were investigated by reflection high energy electron diffraction (RHEED) and high resolution transmission electron microscopy (HRTEM).
Desorption Kinetics of Indium at the InAs/GaAs(001) Heterointerface
Authors: Kaspi Ron , Evans Keith R.
Published: March 2011

Desorption Mass Spectrometry (DMS) is used to monitor In desorption kinetics at the InAs/GaAs (001) heterointerface. In incorporation is determined to be significantly affected by temperature, surface reconstruction, and the V/III flux ratio. It is shown that the onset of the As-stabilized (2×4)-to-In-stabilized (4×2) surface phase transition is surface stoichiometry dependent, and that both the As-stabilized and the In-stabilized surface exhibit first order desorption behavior. Desorption activation energy of In from the (2×4) and the (4×2) surface is measured. In addition to an In-stabilized regime, an In-accumulated regime is identified by its deviation from first order desorption behavior.