Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 71: Metal substrates: Epitaxy and growth
O 71.8: Vortrag
Donnerstag, 25. März 2010, 16:45–17:00, H31
Anomalous Size-Dependent Reconstruction Behavior of Cu-Islands on Ag(100) — •Michael Rieger1, Christopher Zaum2, Karina Morgenstern2, and Karsten Reuter1,3 — 1Fritz-Haber-Institut, Berlin (Germany) — 2ATMOS Leibniz Universität Hannover, (Germany) — 3Technische Universität München, (Germany)
Fast-STM reveals an unusual structure and mobility of smaller Cu-islands on clean Ag(100) at room temperature. Small islands show a complex structure with Cu atoms also adsorbed in bridge sites, and a diffusivity and decay time that is significantly higher than any previously measured value. These observations are supported by our DFT calculations, which indicate a complex reconstructed structure of islands in this size range. Driven by the large lattice mismatch between Ag and Cu, this reconstruction enables shorter Cu-Cu bonds and thereby a stabilization through intra-island strain release. With the concomitantly weakened Cu-Ag bonds, the computed lower binding energy of reconstructed islands to the Ag(100) substrate is consistent with the measured higher diffusivity. In order to better explore the configuration space of island structures we validate an EAM potential for the Ag/Cu system against our DFT data set and employ it for an extensive structure search. The semi-empirical potential enables us to predict a critical island size for the reconstruction that is in perfect agreement with the experimental estimate for the shape turnover.