An ordered surface alloy formed by attractive interaction between coadsorbates: c(2×2) on Cu(0 0 1) by Mg and Bi

Abstract

The coadsorption of dissimilar metals, Mg and Bi, on Cu(0 0 1) at room temperature was studied using low energy electron diffraction (LEED). Five LEED patterns were observed at various coverages: c(2×2), c(4√2×2√2) R45°, c(6×4), c(6×6) and p(4×4). The c(2×2) structure was determined by a tensor LEED analysis. Mg atoms substitute for every second Cu atom in the top layer, and Bi atoms are located at the on-top sites of the remaining surface Cu atoms. The structure parameters demonstrate that Bi atoms pull up Mg atoms located in the substitutional sites, indicating a direct, attractive interaction between coadsorbates. Reasons for the formation of the c(2×2) structure are discussed in comparison with the surface structures formed by the individual adsorption of Mg and Bi.