Spectroscopic confirmation of STM derived Ag/Pt mixing in annealed Ag submonolayers at Pt(111) surfaces

Abstract

Ag3 d 5 2 XP and CO thermal desorption spectra of Pt(111) surfaces covered with Ag submonolayers and annealed at 760 K confirm AgPt monolayer-confined mixing as inferred from recent STM investigations. The Ag3 d 5 2 binding energy in annealed submonolayers is found up to 0.3 eV lower than at adsorbed Ag on Pt(111), explained by increased Pt-coordination of Ag in the mixed layer. The introduction of modified Pt derived adsorption sites, Pt cluster sites, at mixed layers is observed in CO desorption spectra. In accordance with the STM results the fraction of cluster sites is found to grow at the expense of terrace sites at Ag coverages above 0.5 monolayers until the Ag monolayer is completed.