Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 75: Nanotribology II

O 75.1: Vortrag

Donnerstag, 25. März 2010, 15:00–15:15, H36

Atomic Friction on Electrode Surfaces — •Nikolay Podgaynyy and Helmut Baltruschat — University of Bonn, D-53117 Bonn, Germany

Friction under ambient conditions often involves wet surfaces, and thus electrochemical interfaces. Yet, measurements of friction at an atomic scale under electrochemical conditions are scarce. For HOPG, a change of friction forces at steps edges was observed with a change of potential. We recently started to measure friction by AFM and the influence of potential, Cu UPD on Au(111) and other parameters thereupon. We will present friction measurements performed on Au(111) single crystal electrodes and the effect of potential thereupon. Friction increases upon adsorption of anions (sulphate). An increase of friction is also observed at step edges. Here, a careful analysis is necessary to separate geometric effects from true changes of friction. The range of a normal force necessary to observe stick-slip resolution depends on the type of ionic adsorbates and tip radius. Atomic resolution is easily observed if sulfate anions are adsorbed on the gold or copper submonolayer surface. However, with the type of cantilever we used, it was not possible to observe stick-slip resolution on a monolayer of Cu on Au(111) and on Cu bulk deposits. In contrast to Couloumb*s friction law the tip scan rate has an influence on the friction force, however, only when sulfate is adsorbed on the clean Au surface. Such effects were found and explained with conditions when atomic stick-slip occurs.