Friction force microscopy at a regularly stepped Au(665) electrode: Anisotropy effects

Using friction force microscopy, friction was determined for the AFM-tip scanning parallel and vertically to the monoatomic steps of Au(665) electrode for different coverages of Cu in sulfuric acid. When the tip was scanning parallel to the steps, the results were similar to those obtained before for a Au(111) surface: a higher coverage of Cu leads to an increased friction. However, differently from Au(111), no transitions in the friction coefficient were observed with increasing load. Atomic stick slip was observed both for the Au surface and the 3 × 3 honeycomb Cu adlayer with a Cu coverage of 2/3. When the tip was scanning perpendicular to the steps, friction did not depend much on coverage; astonishingly, atomic stick slip was also observed.