| Theoretische Aspekte des Wachstums auf ein und zwei dimensionalen verzerrten Kristalloberflächen |
Schlüsselwörter:
epitaxial growth, strain, transitions metals, self diffusion, exchange diffusion, surface reconstruction, Ehrlich-Schwoebel barrier, iron (110), anisotropic diffusion, relaxation
Epitaktisches Wachstum, Verzerrungen, Übergangsmetalle, Diffusion, Austauschdiffusion, Oberflächen Rekonstruktion, Ehrlich-Schwoebel Barriere, Eisen (110), anisotrope Diffusion, Relaxationsphänomene
Sachgruppe der DNBAbstract
Elastic strain, which appears especially in heteroepitaxial growth, has an important effect on the resulting growth morphologies. To study this phenomenon, the strain dependence of the microscopic diffusion barriers were calculated for transition metals with fcc and bcc structure, using empirical many-body potentials. Two major trends were found: On the fcc(100) surface the barrier for the process of exchange diffusion is reduced with increasing isotropic tensile strain. On the other hand, the additional Ehrlich-Schwoebel barrier at the step edge is increased under tensile strain, as long as exchange diffusion is the preferred diffusion mode in the unstrained systems, as e.g. in the case of gold. Taking into account especially inhomogeneous strain at island borders due to relaxation effects, a careful analysis of microscopic properties, like diffusion barriers and binding energies, leads to the conclusion that the layer-by-layer growth of systems which prefer exchange diffusion should be improved under compressive strain. This conclusion was supported by kinetic Monte Carlo(KMC) simulations of a simplified system. In addition to Pt, Au, Ir and Al, which where expected to prefer diffusion by atomic exchange before, also Pb was found to be a potential candidate for this diffusion mode. Finally, comparing KMC simulations with experimental results for the homoepitaxial growth of Fe/Fe(110), it was shown that the barriers obtained from empirical many body potentials can be successfully used as input parameters for such simulations. The important details of in-situ scanning tunneling microscope pictures were reproduced by the KMC calculations.
| Betreuer | Wolf, D.E.; Prof. Dr. |
| Gutachter | Wolf, D.E.; Prof. Dr. |
| Gutachter | Entel, P.; Prof. Dr. |
| Upload: | 2000-02-07 |
| URL of Theses: | http://www.ub.uni-duisburg.de/diss/diss0005/diss_a.schindler_99.pdf |