Potential-Induced Strain Relaxation in Au Mono- and Bilayer Films on Pt(111) Electrode Surfaces

In situ scanning tunneling microscopy observations of 1–2 monolayer thick Au films on Pt(111) electrodes are presented, which show a complex, potential-dependent structural phase behavior of the Au film. Starting from a pseudomorphic structure at [Formula presented], a sequence of transitions into dislocation network structures occurs with increasing potential: [Formula presented] “striped phase” [Formula presented] “hex phase” in the Au bilayer, [Formula presented] striped phase in the Au monolayer. This is explained by a reduction of the in-plane stress in the Au surface layer(s) due to anion adsorption and a strain energy minimization as described by the Frenkel-Kontorova model.