We have investigated the behavior of nano-islands located on an Au(1 0 0) single crystal surface and the potential dependence in a sulfuric acid aqueous solution containing chloride anions (Cl- anions) at room temperature using electrochemical atomic force microscopy (EC-AFM) at 850 and 1050 mV (versus standard hydrogen electrode, SHE). The number of atoms in the top layer linearly decreases with time, and the decay rate of the nano-islands at 1050 mV become faster than at 850 mV. These results agree with those obtained in a pure sulfuric acid aqueous solution from our previous study. We also found that the decay rate of nano-islands in sulfuric acid solution with Cl- anions is faster than that in sulfuric acid solution without Cl- anions. (C) 2004 Published by Elsevier B.V.