In situ video-scanning tunneling microscopy studies of the structure and dynamics of Cl adlayers on Au(1 0 0) electrodes

The chloride adlayer on Au(1 0 0) electrodes in 0.01 M HCl solution was studied on the atomic scale by in situ high-speed scanning tunneling microscopy. In the potential regime 0–0.4 VAg/AgCl a hitherto not reported defective c(2 × 2) structure was observed. In addition to characteristic straight domain boundaries oriented along the [0 1 0] and [0 1 1] directions of the Au substrate, unusual chain-like adsorbate structures were found. These defects can exhibit open structures with locally lower coverage as well as more close-packed arrangements, in which the adsorbates deviate from the lattice sites and have a 15% reduced nearest neighbor spacing. Dynamic fluctuations within the adlayer occur on the time scale of seconds, much slower than in Cl adlayers on Cu(1 0 0). The increase in defect density observed toward more positive potentials suggests a change of the adsorbate–adsorbate interactions with potential