In-situ atomic-scale studies of the mechanisms and dynamics of metal dissolution by high-speed STM

The fundamental atomic-scale processes during active metal dissolution-the local removal/addition of atoms at atomic kinks in the steps on the crystal surface-were directly studied by novel instrumental methods based on in-si tu scanning tunneling microscopy (STM), using the dissolution of Cu(100) in 0.01 M HCl solution as an example. Direct observation of these rapid dynam ic processes with a novel high-speed electrochemical STM (Video-STM), capab le of acquiring up to 25 atomic resolution images per second, reveals that metal dissolution proceeds at a single type of structurally well-defined ki nks. The reactivity of these kinks is tentatively explained by the coordina tion of Cu surface atoms and Cl adsorbates at these sites. The kinks nuclea te predominantly at outer terraces corners and can condense into larger fac ets, resulting in an apparent 'collective' local dissolution or growth of t erraces. Quantitative data on the kink dynamics were obtained by an alterna tive approach (TOW-STM) and show pronounced local dissolution/redeposition fluctuations at the individual kinks even at the onset of Cu dissolution wi th average kink propagation and reaction rates at kinks in the range 10(3) and 10(5) atoms s(-1) respectively. (C) 2001 Elsevier Science Ltd. All righ ts reserved.