Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 68: Metal Substrates: Solid-Liquid Interfaces

O 68.1: Vortrag

Donnerstag, 28. Februar 2008, 13:15–13:30, MA 043

In situ STM characterisation of electrochemically prepared ultrathin copper sulfide films on Au(1 0 0) — •Christian Schlaup, Peter Broekmann, and Klaus Wandelt — Institut für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerstr. 12, D-53115 Bonn

An ultrathin copper sulfide compound film was prepared on a Au(1 0 0) electrode using the technique of electrochemical atomic layer epitaxy (ECALE). In a first step, a copper monolayer was deposited on a Au(1 0 0) electrode by Cu underpotential deposition from a sulfuric acid solution. By subsequential electrolyte exchanges this copper film was subjected to a sulfide containing sodium hydroxide solution. In situ STM measurements revealed a close packed commensurate c(2 × 2) adlayer structure indicating a sulfur layer with a significantly increased coverage (Θ_S=0.5 ML) with respect to a sulfur adlayer on a blank Au(1 0 0) surface at the same potential. The relative copper to sulfur ratio of 2:1 within the assumed Cu-S bilayer structure supports an interpretation of this structure as a Cu₂S species, which was already supposed for similar Cu-S compound films on a Au(1 1 1) electrode. These compound films are rather stable in a wide potential range, neither sulfur desorption at lower potentials nor a structural transition pointing to the formation of CuS at higher potentials can be observed. Instead the film dissolves completely at anodic potentials, probably due to the formation of soluble copper-thio-oxo species.