Underpotential deposition and electrocrystallization of metals: an in situ scanning tunnelling microscopy study with lateral atomic resolution

The formation of well ordered 2D metal adsorbate layers in the underpotential range and 3D metal deposits in the overpotential range on foreign substrates has been studied in the model system Ag(hkl)/Pb2+ byin situ scanning tunnelling microscopy (STM) under defined potential control with lateral atomic resolution. The results are compared to electrochemical, morphological, in situ EXAFS and GIXS investigations. In situ STM provides an excellent atomic view of the initial steps of underpotential deposition (UPD) and electrocrystallization of lead onto (100) and (111) silver single-crystal faces. The results indicate a Stranski-Krastanov mechanism of 3D nucleation and growth in this system.