IN-SITU SCANNING-TUNNELING-MICROSCOPY OF UNDERPOTENTIAL AND BULK DEPOSITION OF SILVER ON GOLD (111)

The underpotential deposition (upd) and bulk deposition of Ag on Au(111) has been investigated gated in H2SO4 and HClO4 solutions using electrochemical scanning tunneling microscopy (STM). The upd of Ag occurs in three steps on Au(111) in both solutions. A (root 3 x root 3)R30 degrees structure was found for the first adlayer of Ag in pure H2SO4 solution. In HClO4 solution, a (4 x 4) structure was found in the potential range between 0.85 V and 1.10 V vs. the. A (1 x 1) structure appeared after the formation of the third upd adlayer, indicating that a close-packed Ag layer was epitaxially formed in the third upd process. Bulk deposited Ag films showed a rolling hill structure in the beginning but became smoother with time due to surface diffusion. An Ag(111)-(1 x 1) structure was observed for the bulk deposited Ag surface.