Silver on Pt(100) - room temperature growth and high temperature alloying

Growth of submonolayer to monolayer silver films on the reconstructed Pt(100) 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(100) 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. (C) 2003 Elsevier B.V. All rights reserved.