Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 18: Poster Session I - MA 141/144 (Atomic Wires; Size-Selected Clusters; Nanostructures; Metal Substrates: Clean Surfaces+Adsorption of Organic / Bio Molecules+Solid-Liquid Interfaces+Adsorption of O and/or H; Surface or Interface Magnetism; Oxides and Insulators: Clean Surfaces)

O 18.35: Poster

Montag, 25. Februar 2008, 18:30–19:30, Poster F

Potential induced phase transition of a Cu monolayer on a Au(1 0 0) surface — •Christian Schlaup, Peter Broekmann, and Klaus Wandelt — Institut für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerstr. 12, D-53115 Bonn

Underpotential deposition of Cu on Au(h k l) electrodes has been studied extensively over the past. For underpotential deposition of Cu on Au(1 0 0) electrodes in sulfuric acid electrolytes, these in situ STM studies revealed a commensurate Cu(1 ×1) structure in which Cu adatoms occupy 4-fold hollow sites [1]. Additional quasi-hexagonal Cu adlayer structures with an intermediate coverage identified by STM were traced back to chloride contaminations caused by the reference electrode [1]. However, our own experiments revealed a reversible phase transition between the commensurate Cu(1 × 1) structure at potentials near to Cu bulk deposition and a stripe structure at more positive potentials, near to the dissolution of the Cu upd layer. This phase transition of the Cu adlayer was also observed after exchanging the deposition electrolyte for a blank sulfuric acid solution, pointing to a constant Cu coverage during the phase change. Within a single stripe of the anodic phase, the Cu-Cu distances are shortened perpendicular to the stripe direction whereas between different stripes the Cu-Cu distances are elongated. The potential depended appearance of the two phases points to a stabilisation of the reconstructed phase by (bi)sulfate anions.
F.A. Möller, O.M. Magnussen, R.J. Behm, Phys. Rev. B 1995, 51, 2484.