Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 14: Postersitzung (Adsorption an Oberflächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Phasenübergänge, Rastersondentechniken, Struktur und Dynamik reiner Oberflächen)

O 14.31: Poster

Montag, 8. März 2004, 18:00–21:00, Bereich C

Simulation of self-assembled nanostructure formation during heteroepitaxy of immiscible metals — •T. Volkmann1, F. Much1, M. Biehl1, and M. Kotrla21Institut für Theoretische Physik, Universität Würzburg, Am Hubland, 97074 Würzburg — 2Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic

A variety of material systems, though immiscible in the bulk, form stable alloy layers at the surface. This surface confined alloying presumably serves as mechanism for strain relief but the real microscopic mechanism for formation of multi-component structures and the impact of kinetics are still unclear. We perform Kinetic Monte Carlo simulations of multi-component growth with both lattice and off-lattice models. This allows for the separate treatment of kinetic and strain effects. The key ingredient of the lattice model are effective particle interactions of different strength leading to enhanced step edge diffusion barriers at interfaces of different adsorbate types. In the off-lattice model particles interact via pair-potentials with potential depths and equilibrium distances of the particles as parameters. Our simulations show that surface confined alloying is indeed a possible strain relaxation mechanism. The competition between strain and binding energy is found to yield regular stripe patterns, similar to experimentally observed ones. The edge diffusion barrier between regions of different particles alone already causes a stripe-like separation. This confirmes former conjectures, but strain effects have to be taken into account to achieve a restriction of the stripe width and a pronounced asymmetry in the behavior of the different particle types.

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