Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 56: Symposium: The Solid-Liquid Interface: A Challenge for Theoreticians I

O 56.6: Vortrag

Donnerstag, 29. März 2007, 18:30–18:45, H36

New aspects of the sulfur electrooxidation on Au(1 1 1) - An in situ STM study — •Christian Schlaup, Daniel Friebel, Peter Broekmann, and Klaus Wandelt — Institut für Physikalische und Theoretische Chemie, Wegelerstr. 12, D-53115 Bonn

We have reinvestigated the nature of the ring-like structure of the S-covered Au(1 1 1) surface, which appears both under electrochemical conditions as well as in UHV, respectively. In contrast to previous electrochemical studies, the HS⁻ containing alkaline electrolyte was exchanged, after deposition of 0.33 ML sulfur, for a blank 0.01 M NaOH solution, in order to prevent the formation of amorphous bulk overlayers at higher potentials. Subsequently, the structural and morphological changes of the (√3 × √3)R30^∘ S layer upon potential increase were studied in situ with STM. Significant Au mass transport perpendicular to the surface with the formation of vacancies and new islands could be observed. The new islands have an ordered rhombic lattice which consists of the known ring-like units. This observation strongly suggests the formation of an Au_xS compound in contrast to the traditional view of the formation of S₈ species. During the growth of Au_xS islands, S atoms are consumed from the (√3 × √3)R30^∘ structure. Due to the high electrode potential, S atoms are rather immobile, in particular at upper step edges, which enabled us for the first time to image S-covered (√3 × √3)R30^∘ islands along with uncovered (1 × 1) regions simultaneously.