In-situ Scanning Tunneling Microscopy Studies of the Underpotential Deposition of Lead on Au(111).

A modified scanning tunneling microscope was used insitu to study topographic changes on the surface of a Au(111) electrode when a monolayer of lead was deposited from an aqueous electrolyte. By immersing three electrodes and the STM tip in electrolyte, single atomic steps on Au(111) were imaged during the deposition. Comparison of STM images of a 400 x 400angstroms area of the gold before and after deposition shows that small pits in the surface are filled in and that the size of the flat terraces is increased after the lead deposition, giving a smoother surface. These topographic changes are ascribed to the formation of an essentially conformal layer of lead over the gold. However, the pit sites and terrace boundaries display topographic changes due to additional lead-on-lead bonding at step edges.