NANOSCALE STUDIES OF AG ELECTRODEPOSITION OM HOPG(0001)

The electrodeposition of Ag on HOPG (0001) substrate is studied using conventional electrochemical methods (cyclic voltammetry, chronoamperometry) and in situ scanning tunnelling microscopy (STM). Due to a weak substrate-deposit interaction the deposition of kg occurs according to a Volmer-Weber island growth mechanism. At relatively low overpotentials the electrodeposition reaction is mainly initiated on steps and other surface defects. The initial deposition kinetics can be described by a model involving progressive nucleation on active sites and diffusion-controlled 3-D growth. The analysis of experimental results shows that the 4-atomic Ag cluster represents the critical nucleus in the overpotential interval -35mV < eta < -10mV. It is demonstrated that local nanoscale deposition of Ag on flat HOPG (0001) terraces can be induced using STM technique and specific pulse polarisation routines.