Sequentialin situSTM imaging of electrodissolving copper single-crystal domains in aqueous perchloric acid: Kinetics and mechanism of the interface evolution

Abstract

The evolution of Cu crystal surfaces in an aqueous perchloric acid solution at both null $(j=0)$ and constant anodic apparent current density $(j=6\ensuremath{\mu}{\mathrm{A}\mathrm{}\mathrm{cm}}^{\mathrm{\ensuremath{-}}2})$ at room temperature was followed by in situ scanning tunneling microscopy sequential imaging. For $j=0,$ the Cu surface turns out to be highly dynamic as terrace growth, step displacement, and smoothening of small pits can be observed. These processes lead to a small decrease in the value of the root-mean-square roughness (\ensuremath{\xi}). On the other hand, for $j=6\ensuremath{\mu}{\mathrm{A}\mathrm{}\mathrm{cm}}^{\mathrm{\ensuremath{-}}2},$ an inhomogeneous attack proceeds with a marked increase in \ensuremath{\xi}. In this case, while some surface domains become progressively rough others develop nm-sized etched pits that turn the interface unstable. The evolution of the Cu topography under the experimental conditions of this work was simulated using a Monte Carlo algorithm based on a dissolution model in which surface processes are influenced by inhomogeneity stabilizing cavities.