Molecular dynamics simulations, utilizing the Tersoff many-body potential, were used to investigate the effects of 10 eV Si atom bombardment of a (001)2×1 terminated Si lattice. The irradiation events were initiated at an array of points in the primitive surface unit cell. Each event was followed to determine kinetic energy redistribution in the lattice as a function of time, projectile and lattice atom trajectories, and the nature, number, and depth of residual defects. Dimer breaking, epitaxial growth, position exchange, and the formation of residual hexagonal and split interstitials were observed. There were no residual vacancies. Impact points leading to each of the above results clustered in distinctly different regions of the surface unit cell. Bulk interstitials were annealed out over time scales corresponding to monolayer deposition during Si MBE.

Radiation-induced amorphization of the crystalline compound CuTi was investigated by molecular-dynamics simulations using new interatomic potentials derived from the embedded-atom method. Two different approaches to amorphization were tried: one in which Cu and Ti atoms were randomly exchanged, and another in which Frenkel pairs were introduced at random. The potential energy, volume expansion and pair-correlation function were calculated as functions of chemical disorder and atomic displacements. The results indicate that, although both chemical disordering and point-defect introduction increase the system energy and volume, the presence of Frenkel pairs is essential to trigger the crystalline-to-amorphous transition.

In this work the processes of electron-electron interaction taking place in a highly excited electron gas are analyzed on the basis of molecular dynamics simulations. The time evolution of the system is described by using either classic mechanics or a quantum mechanical representation. New aspects of the collective behaviour of the particles are born out by the simulations.

After implantation into Ni at room temperature, Kr condenses under high pressure as an fee solid aligned with the Ni lattice. Evolution of these precipitates during subsequent thermal annealing to a temperature of 650 C has been followed with transmission electron microscopy and modeled with rate theory.

Room temperature implantation results in a monomodal size distribution of small solid Kr precipitates. When Kr is implanted into Ni at 500 C, some precipitates grow to larger sizes, and the precipitate size distribution becomes bimodal. Annealing to temperatures below 600 C after room temperature implantation produces a bimodal size distribution consisting of small solid Kr precipitates and large Kr bubbles. Annealing above 600 C leads to more complete precipitate motion and coalescence that eliminates all small precipitates and results in a monomodal size distribution of large faceted bubbles.

Rate-theory modelling of Kr implantation into Ni at 500 C suggests that small solid Kr precipitates are immobile and that Kr melting is required for precipitate mobility. Similar calculations for thermal annealing experiments show that the bubble size distribution becomes bimodal when only a small fraction of the small precipitates melt and become mobile during annealing, while the size distribution remains monomodal when all precipitates become mobile after Kr melting at higher temperatures.

Fully dynamical computer simulations have been used to study the physical mechanisms of ionized cluster beam deposition. Clusters containing 92 atoms were directed at <001> surfaces with energies per cluster atom ranging from one sixth to three times the cohesive energy of the target. Simulation events employed either Lennard-Jones or Embedded Atom Method potentials. The atoms in the cluster appear to undergo local melting on impact with the substrate. Higher cluster energy increases the spreading of cluster atoms on the substrate and improves epitaxy, but it also increases interdiffusion and produces point defects.

Results from computer simulation and experiments on ion scattering and sputtering processes in ion beam sputter deposition of high Tc superconducting and ferroelectric thin films are presented. It is demonstrated that scattering of neutralized ions from the targets can result in undesirable erosion of, and inert gas incorporation in, the growing films, depending on the ion/target atom mass ratio and ion beam angle of incidence/target/substrate geometry. The studies indicate that sputtering by Kr+ or Xe+ ions is preferable to the most commonly used Ar+ ions, since the undesirable phenomena mentioned above are minimized for the first two ions. These results are used to determine optimum sputter deposition geometry and ion beam parameters for growing multicomponent oxide thin films by ion beam sputter-deposition.

In this work a formalism for the evaluation of electronic losses of heavy ions with energy of few MeV in crystalline semiconductor targets is presented. The stopping values are used in a Monte Carlo simulation to calculate the ion range in silicon and in gallium arsenide for a random orientation of the target and under channelling conditions.

The spectral emissivity of a semi-transparent thin film on a heated substrate varies with film thickness due to optical interference within the layer. This leads to oscillations in the emitted blackbody radiation intensity when the film thickness changes with time. We show how measurements of these oscillations have been used to determine the crystallization kinetics and optical constants of ion-implanted amorphous Si and Ge layers undergoing solid phase epitaxial crystallization. A comparision of emission and reflectivity data illustrates that the emission behavior can be understood in terms of a straightforward optical model.

The scanning tunneling microscope (STM) has been used to investigate graphite surfaces roughened by 5 keV Ar+ ion bombardment. The (0001) surfaces of several samples were etched with the same total ion dose but with different sputter rates for each surface. STM images taken after sputtering show that the roughness of the sputtered surfaces depended on the sputter rate and that the surface topography of each sample appeared self-similar over a large range of length scales. These experimental observations agree with predictions of the recently proposed Shadow Model. The two dimensional height-height correlation function is utilized as a means of quantitative analysis for STM topographs of sputtered surfaces.

Compositional deviation from the standard stoichiometry of tin-oxide and silicon-oxide lines masklessly deposited by laser-induced thermochemical reaction was investigated by micro Rutherford backscattering (RBS). Micro-RBS spectra of the lines deposited with various laser powers indicated that the stoichiometry of the deposited lines for both tin-oxide and silicon-oxide was improved by the increase in laser power. A tomographic image of the tin-oxide line showed a compositional inhomogeneity across the line.

A key element of recent assertions of "cold fusion" has been the claim that electrochemical loading of deuterium into Pd electrodes can produce D:Pd levels exceeding 1:1. Using external beam nuclear reaction analysis of Pd foil electrodes in operating electrochemical cells, we have directly monitored deuterium content in-situ. No conditions were found which resulted in loadings higher than ∼0.9.

A wide variety of materials which are normally undamaged when exposed to a lOOkeV electron beam in a conventional transmission electron microscope can be modified on a nanometre scale by the high current density electron probe in a dedicated scanning transmission electron microscope (STEM). A stationary 100keV STEM electron probe can produce holes typically l-5nm diameter through crystalline Al, Si and MgO tens of nanometres in thickness, while a scanned electron beam can smooth surfaces on an atomic scale.

In Al the stationary electron probe in the STEM produces a row of facetted voids along the irradiated volume. The voids grow initially inwards from the electron exit surface, with each void typically 4nm in diameter and 12-24nm in length, separated by equal distances from one another. In contrast, continuous holes 1.2-1.6nm diameter form at the electron exit surface of Si when exposed to the focused electron beam. However, these holes form only at specific randomly distributed points separated from one another by 2-4nm over the surface of crystalline specimens of both n- and p-doped <001> and <111> Si.

Square cross-section holes with widths of about lnm can be formed by the stationary electron probe in MgO crystals. Rastering the probe over a restricted area of MgO initially results in the rapid development of surface islands and channels which are subsequently removed to leave an atomically smooth surface.

A microbeam line with precisely designed quadrupole magnets has been developed and installed at the Research Center for Extreme Materials, Osaka University. For the purpose of applying the beam line to microbeam RBS/channeling, the damage in <100>Si due to the irradiation of probe beams was studied as a function of incident ion dose from 1015 to 1018 /cm2 with a flux of 8 × 104 nA/cm2. It was found that the dose for channeling measurements should be less than several 1017 /cm2.

The dependence of the ordering factor and surface roughness of aiorphous SiO2 and Ni filis fabricated by Dual Ion Beai Sputtering(DIBS) assisted by Ar+ ion boibardient were evaluated. The ordering factor tas defined as a quantity which shows the degree of aiorphousness froi ris value of correlation function of the RHEED pattern. The surface roughness was leasured with a Talystep systei and STM, and the data was evaluated with respect to the spatial wavelength.

For aiorphous SiO2 filis, the surface roughness is strongly correlated with the ordering factor as a parameter of the assisting Ar+ ion energy, and it depends on the fill structure. Siiilar relationship was not observed for Ni filis, because of the traced surface roughness of substrate in the energy region investigated.

Fingernails from several sources were studied to determine elemental compositions. The common elements were found to be H, C, N, O, Ca and Fe. The elements Si, Bi, S, Mo, Ti, Zn, Pb, P and Nd were found on some of the nails; these are considered to result from environmental contamination, food and water intake. The compositions of H, C, N and O correlate with those in the hemoglobin molecule and, they do not vary significantly with time. This suggests that they are associated with dead blood cells. The other common elements, such as Ca and Fe, show variations in composition with time, probably because their amount in the body is determined by food and water intake. Fingernails from female sources have a higher concentration of Ca than those from male sources. Also, the concentration of Ca is generally higher on the outer than the inner surface of the nail, probably to provide a stronger bony structure and mechanical strength on the outside.

The techniques of single and double layers of implanted Xe ions marker as well as the O18 tracing method are used to study the mechanism of the anodic oxidation of Ti and TA6V (Ti6A14V). It is observed that in 5 wt% ammonium citrate, the mechanism of the anodic oxidation of Ti is very different from that of TA6V. For Ti, new oxide is formed mainly by the migration of Ti cations to the solution/oxide interface and the regions at which new oxide is formed are at the solution/oxide interface and in the pre-oxide near the interface. While for TA6V, anodic film growth is due to the migration of oxygen anions to the oxide/metal interface and the growth regions of new oxide are at the oxide/metal interface and in the pre-oxide near the interface. Transport numbers for Ti oxidized in 1 wt%. KOH are calculated and found to be affected by oxidation temperature, i.e. at 3'C, the average transport number is 0.32, while at 30&00B0;C,it is 0.28. Current efficiencies are above 99.8%. AES spectra show that the distribution profiles of the elements V and Al in anodic film on TA6V are uniform.

Recent applications of the transient conductance technique to measurements of thermodynamic properties of Si are reviewed. The transient conductance measurements provide time-resolved data of the melt and solidification dynamics during pulsed laser irradiation. By studying these dynamics, thermodynamic properties can be measured in time and temperature regimes unaccessible by conventional techniques. Examples discussed include homogeneous nucleation, electrical properties of the supercooled liquid, and the melting temperature of amorphous Si. Homogeneous nucleation occurs at supercoolings of 500 K for quench rates near 1010 K/s, consistent with a liquid/crystal surface energy of 0.34 J/m2. Evidence of transient nucleation effects are observed at quench rates above 2 × 1010 K/s. During supercooling, the temperature dependence of the electrical conductivity of liquid Si was estimated between 1200 and 1800 K with a broad maximum observed near 1450 K. The melting temperature of amorphous Si was determined to be 220 K below the crystal melting temperature with no detectable differences between thermally unrelaxed and relaxed states.

Pulsed laser irradiation is used to induce epitaxial explosive crystallization of amorphous silicon layers buried in a (100) oriented crystalline matrix. This process is mediated by a self-propagating liquid layer. Time-resolved determination of the crystallization speed combined with numerical calculation of the interface temperature shows that freezing in silicon saturates at 16 m/s for large undercooling (> 130 K). A comparison between data and different models for melting and freezing indicates that the crystallization behavior at large undercooling can be described correctly if the rate-limiting factor is assumed to be diffusion in liquid Si at the solid/liquid interface.

We have performed nanosecond-resolution measurements of the lateral electrical resistivity of thin metal films on insulating substrates. Comparison of transient resistivity measurements with optical reflectivity measurements and heat-flow calculations permits the determination of the position and velocity of a planar crystal/melt interface, and an estimate of undercooling during pulsed laser melting of metals. We report detailed results for rapid solidification of Ni, including the observation of hypercooling of .liquid Ni.

The optically induced spin polarization P of the photoelectrons emitted from tin and germanium during ps and ns laser pulses is measured as a function of the pulse energy. P is defined by the lattice symmetry of the sample. It vanishes for amorphous or molten surfaces. The melting of the metal and the semiconductor is found to occur on a time scale which is short compared to the duration of a 70 ps laser pulse. The emission of positive ions starts at the laser intensity for which the drop of the polarization is observed. If Ge is heated with ns laser pulses a temperature dependent shift of the work function causes a decrease of the spin polarization for laser energies far below the energy necessary for melting. With ps laser pulses the polarization only vanishes for pulse energies exceeding Eion- The difference between the ps and ns measurements on Ge points to an unexpected dynamical behavior of the work function shift in semiconductors.