In situ Scanning Tunneling Microscopy of the Electrochemical Deposition of Ag on Graphite

A scanning tunneling microscope (STM) has been constructed to observe the surface change of a working electrode during the electrochemical reactions in electrolyte solution. Both potentials of STM tip and substrate with respect to a reference electrode can be independently controlled by simply combining with a commercially available potentiostat and the STM. These types of apparatus are used to study the electrochemical deposition of Ag on a highly oriented pyrolytic graphite (HOPG) substrate in HClO4 solution. Before Ag deposition and after stripping the Ag film, atomic images of HOPG surface are obtained. The STM images of Ag deposit produced by cyclic voltammetric and potential pulse methods are observed. The observed STM images support the conclusion that the electrodeposition occurs according to the island growth mechanism.