STM tip-induced local electrochemical dissolution of silver

Local dissolution/deposition processes under in situ scanning tunneling microscopy (STM) imaging conditions are studied in the systems Ag(111)/Ag+, ClO4- and Ag(111)/Ag+, SO42-. The results show that in both systems the local kinetics of these processes strongly depend on the polarization conditions. At STM-tip potentials more positive than the Ag/Ag+ equilibrium potential, a local dissolution of the Ag(111) substrate is observed even at cathodic substrate overpotentials at which the overall substrate current density is cathodic. This tip-induced Ag dissolution is in agreement with results obtained recently in the system Cu((111))/Cu2+. The enhanced local Ag dissolution is explained by a reduced Ag+ concentration underneath the STM tip promoted by both an electrostatic repulsion of Ag+ and a reduction of the mass transport due to the shielding effect of the tip. The possibility for a preparation of negative Ag nanostructures by STM tip-induced electrochemical dissolution is demonstrated. (C) 2003 Elsevier Science Ltd. All rights reserved.