bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of the Chemical Potentials of Highly Supersaturated Cu-Co Alloys
Authors: Gärtner F. , Busch R. , Haasen P. , Bormann R. 
Published: April 2011

AbstractWith the CALPHAD approach based on the regular solution model, the thermodynamic functions of the Cu-Co system can be extrapolated to compositions where the homogeneous fee solid solution is thermodynamically unstable. Up to now it has been unclear how reliable such extrapolations are in view of the driving forces for decomposition and whether the Gibbs energy is well described by the model in the unstable region. Therefore, electromotive force measurements were performed to determine directly the chemical potentials of highly supersaturated Cu-Co alloys. Under the prerequisite that time scales of the electrochemical exchange reaction are fast compared with the kinetics of decomposition, the thermodynamics of the alloys can be investigated quasi statically. Within the experimental accuracy the results for both a metastable and an unstable alloy agree well with the calculated chemical potentials. In addition, the experiments demonstrate that the electrochemical cell reaction is reversible upon small external concentration fluctuations of the investigated alloys. Possible reasons for this unexpected stability are discussed taking the kinetics of the decomposition into account.
Diffusion Enhancement in Glassy Metals Under Non-Equilibrium Conditions
Authors: Bellini S. , Mazzone G. , Montone A. , Vittori-antisari Enea M. , Casaccia C.R. 
Published: April 2011

AbstractThe diffusion properties of a Ni-Zr metallic glass formed at the interface of a bulk diffusion couple have been studied in conditions far from a fully relaxed state. The growth kinetics of the interface film have been enhanced by both plastic deformation and high energy electron irradiation. Different results have been obtained in the two cases, since in the first case the film grows exponentially with time, while in the second case the usual square root dependence on time is observed. This behaviour has been interpreted as a consequence of the annihilation kinetics of the excess free volume introduced in the glass by the above methods. Two different mechanisms of free volume annihilation , namely exchange with a crystal vacancy at the glass-crystal interface and structural relaxation in the bulk glassy phase have been considered to be operative so that the nature of the growth kinetics has been found to depend on the mechanism predominant in each experimental condition.
Effect of In-Situ Formation of Nanoscale γ-Al2O3 and AlN on Thermal Stability of Cryomilled Nanocrystalline Fe
Authors: Perez R.J. , Huang B. , Lavernia E.J. 
Published: April 2011

AbstractCryogenic attritor milling (cryomilling) is used to synthesize nanocrystalline Fe-10wt.%Al powders. Following consolidation in a rigid die at 823 K and heat treatment for 1 hour at 1223 K, an average grain size of 16±7 nm is maintained. This level of thermal stability is shown to exceed that of pure Fe processed under identical conditions. The significant increase in thermal stability is attributed primarily to the presence of nanometer-scale γ-Al2O3 and AIN dispersoids formed during cryomilling and subsequent heat treatment.
Synthesis of Granular Systems by Cluster Beam Deposition
Authors: Pollack Margolita , Herr Ulrich , Averback R.S. 
Published: April 2011

AbstractGranular films were prepared by simultaneous cluster beam and physical vapor deposition. The clusters are formed by high pressure sputtering and have an average size between 2 and 5 nm. This method makes it possible to control the granule size and concentration, which is not possible using precipitation synthesis of granular alloys. Most importantly, a diverse set of granule/matrix systems are accessible by this system. The method is illustrated for systems of interest for giant magneto-resistance applications: Co/Cu (miscible), and Co/Cr (immiscible.) Synthesis of films with isolated embedded clusters of more complex structures, e.g. intermetallics Ni3Al and Cu3Au, are also discussed.
Nanostructured Silver Particles Embedded in a Silica Matrix
Authors: Lee M. H. , Dobson P. J. , Cantor B. 
Published: April 2011

AbstractA series of different nano-sized silver particles has been prepared using r.f. magnetic plasma co-sputtering apparatus. A combination of high-resolution lattice images and optical diffractograms has been used to characterize the atomic structures during nucleation and growth of silver particles embedded in a silica matrix. For particles with diameter of 2 ∼ 5 nm, most have single crystal structures, but some have singly twinned morphologies and a few have multiply twinned morphologies. In those particles, there are many defects such as dislocations, stacking faults, twin boundaries and lattice fringe bends. For particles with diameter of 5 ∼ 9 nm, we can detect some single crystals, singly twinned particles and multiply twinned particles including decahedral and icosahedral particles. Anomalous meta-stable structured particles with 90° cross {111} lattice fringes have been also found. For particles with diameters of larger than ∼ 9 nm, most have multiple lamellar twins and sometimes there are macroscopically irregular shaped particles.
Titanium Silicidation Induced Point Defects in SI
Authors: Herner S. B. , Gossmann H.-J. , Jones K. S. 
Published: April 2011

AbstractAntimony and B-doping superlattices were employed to study the population of Si native point defects after the formation of a TiSi2 film at 800 to 890°C. Formation of a TiSi2 film at these temperatures results in interface roughness on the order of 300 Å (root mean square). Artifacts in SIMS data arising from sputtering through such a rough interface were avoided by chemomechanical polishing of the underlying Si after chemically etching off the TiSi2 film. The resulting Si surface had a roughness of 0.7 Å. Enhancement in the diffusion of Sb and retardation in the diffusion of B over control samples without a TiSi2 film indicate a vacancy supersaturation and an interstitial undersaturation.
Beem and UHV-TEM Studies of PtSi/Si(001)
Authors: Kavanagh K. L. , Morgan B. A. , Talin A. A. , Ring K. M. , Williams R. S. , Reuter M. C. , Tromp R. M. 
Published: April 2011

AbstractRecent work using ballistic electron emission microscopy (BEEM) and ultra-high vacuum transmission electron microscopy (UHV-TEM) to study structure-property correlations of PtSi/Si(001) contacts is described. The spatial uniformity of the Schottky barrier height (SBH) for diodes grown at room temperature and 350°C was compared with the interface microstructure using TEM. Narrow SBH distributions with standard deviations of 7–12 meV were obtained independent of the deposition system and temperature. Analysis of the distributions compared well with standard current-voltage and capacitance-voltage measurements on the same diode. These low temperature depositions produced fine grained PtSi films (10–20 nm) with an interface roughness dependent on the cleaning process. Probable orientation effects on the SBH distribution were apparently screened out because of the low doping of the substrates that were used. As the deposition temperature is increased the PtSi tends towards polycrystalline epitaxy with island growth beginning at 700°C. Grains are rectangular and develop a large shape anisotropy of great interest for future investigations.
Electrical and Structural Characterization of Ti Contacts to Si0.89 Ge0.11/Si(001) Epilayers
Authors: Lyakas M. , Beregovsky M. , Moskowitz I. , Eizenberg M. 
Published: April 2011

AbstractThe properties of thin (350 Å) Ti layers deposited on Si0.89Ge0.11 layers epitaxially grown on Si(001) were studied as a function of isochronal (30 min.) thermal treatments in the temperature range Ta=550–800°C. Both as-deposited and annealed at Ta up to 750°C Schottky diodes revealed near-ideal I–V and C–V characteristics with the same flat-band barrier height eV. The results indicate that at these Ta the Fermi level is pinned with respect to the conduction band.Annealing at 800°C resulted in an improvement of the Schottky diodes quality and a drop in and the series resistance Rs of the contacts. The values of the ideality factor n and ( measured were 1.03±0.02 and 0.56±0.007 eV, correspondingly. The electrical parameters of these metal/semiconductor contacts were correlated with the dynamics of interfacial reactions due to the applied heat-treatments.
Barrier Height Control and X-Ray Diffraction Study of Metal on Si1−Gex/Si Grown by Very Low Pressure CVD
Authors: Shiâ Z. Q. , He L. , Zheng Y. 
Published: April 2011

AbstractThe potential application of epitaxial Si1−xGex, on Si in electronic and optoelectronic devices has led to an increased study of metal - Si1−xGex interaction and barrier height control technique. In this paper, we report the epitaxial growth of Si1−xGex on Si and the Schottky barrier formation processing. The Si1−xGex (x=0.17 and 0.20) layers were grown by rapid radiant heating, very low pressure chemical vapor deposition (VLPCVD). The crystal structure and epitaxial nature of the Si1−xGex, layers were studied by X-Ray diffraction. The value of full width at half maximum (FWHM) was found to be 0.34° for the as grown Si1−xGex (400) peak. The metal-Si1−xGex/Si Schottky diodes were formed by depositing Pd on Si1−xGex/Si at room temperature (RT=300K) and low temperature (LT=77K). The Schottky barrier heights and current transport mechanisms were determined by current-voltage-temperature (I-V-T) measurements. The interface property of Pd/ Si1−xGex/Si were studied as a function of metal deposition and post annealing temperatures.
Iridium Silicides Formed by RTA in Vacuum
Authors: Rodríguez T. , Almendra A. , Botella M. , Silva M. F. Da , Soares J. C. , Wolters H. , Ballesteros C. 
Published: April 2011

AbstractThe growth kinetics of the iridium silicides, IrSi and IrSi1.75 formed by RTA in vacuum has been characterized as a function of the processing temperature, up to 675°C, and annealing time for iridium films of different thickness. The sample temperature was measured using as a reference the SPE growth rate of amorphized silicon processed in the same RTA conditions. The samples were characterized by RBS, HREM, XRD and microdiffraction. RBS spectra show that the transition region between IrSi and IrSi1.75 is slightly gradual, while the interface between the IrSi and the iridium metal is sharp. The layer thickness of each silicide as a function of temperature and time was obtained from the RBS spectra. The activation energy of the diffusion coeficient of Si in IrSi and IrSi1.75 are about 1.3 eV and 3.9 eV respectively. Phase kinetics are the same for both thin and thick samples processed at the same temperature and annealing time when unreacted iridium remains in the film. However, the phase evolution is different when the annealing time is long enough to convert all the iridium metal into silicide in the thin film sample but not in the thick one. In this case, IrSil.75 is the only phase found if the annealing time is long enough. Silicides formed at 525°C consist mainly of polycrystalline IrSi, with grain size between 3 and 10 nm, and some isolated grains of IrSi 1.75. The interface between the IrSi and the Si is flat, very sharp, and well oriented grains grow from it. In order to avoid the IrSi1 75 formation and to obtain IrSi layers at reasonable rates, an RTA process at 500°C is proposed.
Study of the Hall-Petch Dependence in an Annealed Nanocrystalline Iron Thin Film
Authors: Savader J. B. , Scanlon M. R. , Cammarata R. C. , Smith D. T. , Hayzelden C. 
Published: April 2011

AbstractThe hardness dependence on grain size of a nanocrystalline iron thin film prepared by sputtering was investigated. The as-deposited film had an initial grain size of 11.4 nm and sections of the film were annealed in a reducing atmosphere furnace to increase the grain size up to 31.5 nm. Hardness was measured by nanoindentation for different grain sizes, and a Hall-Petch plot of hardness versus reciprocal square root of grain size was obtained. This Hall-Petch plot gave a positive slope that was about a factor of seven smaller than the slope obtained from ball-milled iron with grain sizes between 6.0 and 8.5 nm [8].
Thermodynamics of Hole and Hillock Growth in Thin Films
Authors: Srolovitz D. J. , Yang W. , Goldiner M. G. 
Published: April 2011

AbstractThis paper provides a thermodynamic analysis of hole and hillock growth in stressed thin films in simplified geometries. Two limiting cases were considered. In the first, matter is transported to (from) the growing hillock (hole) from (to) the surface of the film. In the second case, the material transported to (from) the growing hillock (hole) comes from (goes to) the interior of the film in the vicinity of the hillock (hole). When bulk relaxation is dominant, hillock growth is favored by a compressive stress in the film and hole growth is enhanced when the film is in tension. This is the commonly observed situation. On the other hand, when surface relaxation effects dominate, hillocks and holes can grow in either tension or compression.
Effects Of Impurities on the Crystallization and Grain Growth of Polycrystalline Si Films
Authors: Paik Jae- Cheol , Park Kwang-Hyun , Choi Woon , Nam Seung-Eui , Kim Hyoung-June 
Published: April 2011

AbstractDevice-quality poly-Si films are used as the active material of poly-Si thin film transistors. Poly-Si films with high crystallinity, which have large grains and/or low intragranular defects, lead to a high device performance. The presence of O or C impurities in the deposited Si films can greatly affect the behavior of crystallization and grain growth of these films, and their resulting crystallinities. A substantial amount of O or C can be introduced in the films during deposition from residual gases in the deposition chamber. Control of base pressure during Si deposition, therefore, will be an important process parameter determining the crystallinity of these films. The effects of the base pressure on the crystallization and grain growth of deposited Si films were investigated using a high vacuum Chemical Vapor Deposition system. Lower base pressure decreases the deposition temperature for the amorphous/crystalline transition of as-deposited films. Crystallization of amorphously deposited films is also affected by base pressure. The kinetics of crystallization and crystallinities of poly-Si films after crystallization are substantially increased by reducing base pressure. Enhanced crystallization kinetics and film crystallinities can be explained by reduced inclusions of O or C impurities in Si films, thus enhancing the atomic mobility. The improved film crystallinity of poly-Si films leads to higher device performance of poly-Si TFT's.
Improved Spray-Pyrolysis Deposition System for Polycrystalline Conductive SnO2 Thin Films
Authors: Foglietti V. , Galbato A. , Bearzotti A. , Galloppa A. , Maltese P. 
Published: April 2011

AbstractBismuth-doped tin oxide films have been deposited using a new spray-pyrolysis deposition system. Among the properties are the possibility of depositing thin films over very large areas with good uniformity and the relatively small cost compared with other types of deposition systems. The apparatus is divided in two major parts, the aerosol chamber and the deposition chamber. The deposition chamber consists of a flat rotating hot plate that can house substrates up to 18 cm in diameter. Deposition temperature ranges from 290 °C to 350 °C. The SEM pictures show a phase transition from amorphous to polycrystalline which also strongly affects the transport properties of the film. The high values of the surface resistivity obtained are consistent with those ones required to develop an analog grey scale ferroelectric liquid crystal display. The sample shows a 20% uniformity in the value of surface resistivity over an area of 140 cm2, and the results obtained until now show a satisfactory reproducibility. Bismuth and Tin concentration versus deposition temperature have been determined by ICP mass spectrometry. Our work is supported by the ESPRIT project “PROFELICITA”.
Structure and Properties of W and Mo-Subcontact Layers Influenced by Thermal Annealing
Authors: Gesheva K. A. , Stoyanov G. , Harizanova A. , Stefanov R. 
Published: April 2011

AbstractOne of the most important problems to solve in order to improve the CdTe solar cell performance is the deposition of stable ohmic contacts. W and Mo with their high work function, high temperature stability and good mechanical properties are prospective materials for contacts to p-CdTe. This paper presents data for the electrophysical characteristics of W or Mo/CdTe and W or Mo/ CdS-CdTe heterostructure systems. W and Mo films are deposited by a W(CO)6 based CVD process at atmospheric pressure and low temperatures (250–300)°C. We emphasize the improvment of the contact properties by developing a transitional layer heavily doped with acceptors. The defects arrangement in the layer should promote the diffusion of such impurities as Cu, P, As etc. A proper balance between the impurities and the defects could be achieved by suitable thermal treatment. Rapid thermal or traditional annealing in different gas atmospheres – N2, Ar or air were applied, followed by chemical or electrochemical treatment. Electrical characteristics measurements and structural studies were performed for CdTe layers as well as for the SnO2 - CdS - CdTe structures
Electron Transport in Highly Textured Metal Films Grown by Partially Ionized Beam Deposition
Authors: Soss S. R. , Gittleman B. , Mello K. E. , Lu T.-M. , Lee S. L. 
Published: April 2011

AbstractIn principle, the resistivity of bulk FCC cubic materials should not depend on the orientation due to the fact that the conductivity tensor is single valued. However, we show that this conclusion is not valid for thin films. Deposition of highly oriented Al, Ag, and Cu films on amorphous substrates using the partially ionized beam (PIB) technique exhibit a resistivity which is strongly correlated with the texture, i.e., the tighter the texture, the lower the film resistivity. We model the film as an array of grains whose grain boundaries can be considered as delta function potentials for electron scattering and the strength of the potentials can be calculated from the measured resistivity of the films. On the other hand, the fiber texture distribution of the the films is obtained from X-ray pole figure measurements, and Monte-Carlo simulations are then performed using this data to determine the average dislocation density at the grain boundaries due to the grain to grain crystallographic mismatch. We show that the transmittance coefficient for electron scattering, and therefore the film resistivity, is a monotonically increasing function of the average dislocation density. We therefore conclude that the structure of grain boundaries in a thin film provides the necessary mechanism by which the resistivity of an FCC cubic metal can depend on the texture.
Characterization of Copper Diffusion into Al and Al-1% Si Polycrystalline Thin Films
Authors: Walsh L. H. , Ramseyer G. O. , Beasock J. V. , Helbig H. F. , MacWilliams K. P. 
Published: April 2011

AbstractAl and AI-1%Si 900 nanometer thin films were deposited on 100 nanometer Cu films on thermally oxidized (100 nanometer) Si wafers. The Al and Cu films were deposited using evaporation techniques, and the Al-1%Si film was sputter deposited. Different thin film samples were heated in vacuum to 175, 250, 330 and 400°C for 1 hour. The various annealed and original samples were compared using surface morphology, as well as composition versus sample depth. Differences between the Al and Al-1%Si samples are discussed.
Independent Optimization of Nucleation and Growth Processes of Titanium-Alloy Underlayers for Cobalt-Alloy Perpendicular Recording Media
Authors: Nolan T. P. , Hirayama Y. , Futamoto M. 
Published: April 2011

AbstractMagnetic recording performance of cobalt-alloy perpendicular media depends upon microstructural features including preferred c-axis out-of-plane orientation, grain size and grain separation. These depend on the titanium-alloy underlayer surface structure, which in turn depends on film nucleation and growth. The Ti-alloy nucleation and growth stages are independently controlled by changing argon pressure during sputter deposition. Ti and Ti90Cr10 underlayers have qualitatively different microstructures, but in each case a two-step deposition process produces a better combination of separated magnetic layer grains and strong preferred orientation than constant argon pressure underlayer media. Correspondingly, media magnetic performance is improved over single pressure depositions. Observed microstructure and magnetic properties are consistent with simple growth models.
Large Scale Molecular Dynamics Study of Amorphous Carbon and Graphite on Parallel Machines
Authors: Yu J. , Omeltchenko Andrey , Kalia Rajiv K. , Vashishta Priya , Brenner Donald W. 
Published: April 2011

AbstractUsing a reactive empirical bond-order potential (REBOP) model for hydrocarbons1, large scale molecular dynamics simulations of carbon systems are carried out on parallel machines. Structural and dynamical correlations of amorphous carbon at various densities are studied. The calculated structure factor agrees well with neutron scattering experiments and the results of tightbinding molecular dynamics simulations. The dynamic behavior of crack propagation through graphite sheet is also investigated with the molecular-dynamics method. Effects of external stress and initial notch shape on crack propagation in graphite are studied. It is found that graphite sheet fractures in a cleavage-like or branching manners depending on the orientations of the graphite sheet with respect to the external stress. The roughness of crack surfaces is analyzed. Two roughness exponents are observed in two different regions.
Ab-Initio Molecular Dynamics of Organic Compounds on a Massively Parallel Computer
Authors: Gygi François 
Published: April 2011

AbstractWe present results of ab-initio electronic structure calculations and molecular dynamics simulations of organic molecules carried out using adaptive curvilinear coordinates, within the local density approximation of density functional theory. This approach allows for an accurate treatment of first-row elements, which makes it particularly suitable for investigations of organic compounds. A recent formulation of this method relies on a real-space approach which combines the advantages of finite-difference methods with the accuracy of adaptive coordinates, and is well suited for implementation on massively parallel computers. We used molecular dynamics simulations to obtain the fully relaxed structures of nitrosyl fluoride (FNO), and of the aromatic heterocycles furan and pyrrole. The equilibrium geometries obtained show excellent agreement with experimental data. The harmonic vibrational frequencies of furan and pyrrole were calculated by diagonalization of their dynamical matrix and are found to agree with experimental data within an rms error of 25 cm-1 and 28 cm-1 for furan and pyrrole respectively. This accuracy is comparable to that attained for smaller organic molecules using elaborate quantum chemistry methods.
Electronic Structure Calculations on a Real-Space Mesh with Multigrid Acceleration
Authors: Sullivan D. J. , Briggs E. L. , Brabec C. J. , Bernholc J. 
Published: April 2011

AbstractWe have developed a set of techniques for performing large scale ab initio calculations using multigrid accelerations and a real-space grid as a basis. The multigrid methods permit efficient calculations on ill-conditioned systems with long length scales or high energy cutoffs. We discuss the design of pseudopotentials for real-space grids, and the computation of ionic forces. The technique has been applied to several systems, including an isolated C60 molecule, the wurtzite phase of GaN, a 64-atom cell of GaN with the Ga d-states in valence, and a 443-atom protein. The method has been implemented on both vector and parallel architectures. We also discuss ongoing work on O(N) implementations and solvated biomolecules.