Silver on Pt(1 0 0)––room temperature growth and high temperature alloying

Growth of submonolayer to monolayer silver films on the reconstructed Pt(1 0 0) surface at 300 K and evolution of the structure with increasing temperature was studied primarily by scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES). At 300 K, formation of elongated 2D-adislands with a composition of Ag80Pt20 was observed. This island stoichiometry is dictated by the amount of Pt expelled due to removal of the hex-reconstruction of the clean Pt(1 0 0) surface by the growing Ag adislands. The island shape can be explained by an anisotropic stability of the reconstruction, with the row pattern of the reconstruction acting as a template for island growth. Annealing of the sample above 600 K causes more extensive alloying starting at the perimeter of the Ag adislands by Ag–Pt exchange and formation of a nanophasic Ag–Pt alloy confined to the surface layer. With sufficient Ag, this alloy spreads across the surface until a uniform stoichiometry is established over the entire surface. Temperature-dependent AES studies indicate that there is some mixing of Ag with bulk Pt at elevated temperatures.