Interaction of gold with clean and oxygen-covered Re(10 anti 10) surfaces

The structure, growth and morphology of thin Au films deposited on both clean and oxygen-covered rhenium (10 anti 10) 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 x 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 x 1) structure (Θ=2), where the heat of sublimation of bulk Au, ΔHsub, 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 x 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 A diameter and 100 A average length which are aligned parallel to the troughs of the Re surface. At elevated temperatures, Au desorbs first from the bulk phase (Edes=ΔHsub), only as oxygen desorption becomes competitive, Au atoms can diffuse to and interact with the bare Re sites and desorb with the characteristic energy.