Regensburg 2010 – scientific programme
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O: Fachverband Oberflächenphysik
O 71: Metal substrates: Epitaxy and growth
O 71.1: Talk
Thursday, March 25, 2010, 15:00–15:15, H31
Interaction of gold with clean and oxygen-covered Re(1010) surfaces — Sebastian Schwede, •Susanne Schubert, Christian Pauls, and Klaus Christmann — Freie Universität Berlin, Takustr. 3, 14195 Berlin
The structure, growth and morphology of thin Au films deposited on both clean and oxygen-covered rhenium (1010) surfaces has been studied as a function of coverage Θ and temperature T using LEED, STM and thermal desorption spectroscopy (TDS). In the absence of oxygen, Au forms a variety of ordered (1× n) phases (n = 3, 4, 5, 6 and 1) with the Au adsorption energy increasing from ∼320 kJ/mol at low Θ to ∼380 kJ/mol near the bilayer (1×1) structure (Θ=2), where the heat of sublimation of bulk Au, Δ Hsub, is reached. Au wets the Re surface completely, for Θ>2, a simultaneous multilayer growth is observed. On the oxygen covered Re surface with its well-known (reconstructed) (1×3)-2O phase (Θ= 2/3), however, Au deposition at 300 K causes immediate 3D clustering with rough and heterogeneous films pointing to a clear non-wetting behavior. Annealing of these films at 850 K gives the Au atoms sufficient mobility to coalesce to cylindrically shaped aggregates of ca. 50 Å diameter and 100 Å average length which are aligned parallel to the troughs of the Re surface. At elevated temperatures, Au desorbs first from the bulk phase (Edes=Δ Hsub), only as oxygen desorption becomes competitive, Au atoms can diffuse to and interact with the bare Re sites and desorb with the characteristic energy.