Electrochemical deposition of Ag and potential-induced structural change of the deposited Ag layer on a 23 x root 3 reconstructed surface of Au(1 1 1) electrode were followed by in situ scanning tunneling microscope (STM). A uniform Ag monolayer was formed on a reconstructed Au(1 1 1) surface in a 50-mM H2SO4 solution at +0.3 V (vs. Ag/AgCl) after adding a solution containing Ag2SO4 so that the concentration of Ag+ in the STM cell became ca. 2 mu M. No characteristic height corrugation such as the Au reconstruction was observed on the surface, indicating that the lifting of the substrate Au reconstruction occurred by Ag deposition. The formed Ag monolayer was converted to a net-like shaped Ag nano-pattern of biatomic height when the potential was stepped from +0.3 to -0.2 V in the solution containing 2 mu M Ag+. This result indicates that the substrate Au(1 1 1)-(1 x 1) surface was converted to the reconstructed surface even in the presence of Ag adlayer. Quite different structure was observed for I'd deposition on a reconstructed surface of Au(1 1 1) electrode at +0.3 V and the origin for this difference between Ag and I'd deposition is discussed. (C) 2009 Elsevier Ltd. All rights reserved