Deposition of silver on the Pt(100)-hex surface: Kinetic control of alloy formation and composition by surface reconstruction

Silver deposition on the Pt(100)-hex surface at 300 K leads to formation of a disordered Pt₂₀Ag₈₀ alloy in the first monolayer. This is due to lifting of the Pt(100)-hex-reconstruction which expels 20% of a monolayer of excess Pt atoms out of hex-reconstruction into the growing Ag film. Such mixing in the first monolayer may be expected generally for film growth on reconstructed surfaces at low temperatures. Our results are compared to a recently published article for Ag growth on Pt(110)-(2×1) surfaces [Surf. Sci. 478 (2001) L345]. For this system as well we suggest that a disordered monolayer-alloy forms with a Pt₅₀Ag₅₀ stoichiometry, instead of Ag growth proceeding by purely filling in the missing rows of the (2×1) reconstruction.