SEQUENTIAL IN-SITU STM IMAGING OF ELECTRODISSOLVING COPPER SINGLE-CRYSTAL DOMAINS IN AQUEOUS PERCHLORIC-ACID - KINETICS AND MECHANISM OF THE INTERFACE EVOLUTION

The evolution of Cu crystal surfaces in an aqueous perchloric acid sol ution at both null (j=0) and constant anodic apparent current density (j=6 mu A cm(-2)) at room temperature was followed by in situ scanning tunneling microscopy sequential imaging. For j=0, the Cu surface turn s out to be highly dynamic as terrace growth, step displacement, and s moothening of small pits can be observed. These processes lead to a sm all decrease in the value of the root-mean-square roughness (xi). On t he other hand, for j=6 mu A cm(-2), an inhomogeneous attack proceeds w ith a marked increase in xi. In this case, while some surface domains become progressively rough others develop nm-sized etched pits that tu rn the interface unstable. The evolution of the Cu topography under th e experimental conditions of this work was simulated using a Monte Car lo algorithm based on a dissolution model in which surface processes a re influenced by inhomogeneity stabilizing cavities.