Formation of a two-dimensional alloy/surface phase: Auger and STM study of Cu(Sn)(111)

Abstract

The segregation of Sn in Cu and the formation of a Sn–Cu surface alloy has been studied by Auger electron spectroscopy (AES), reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). By annealing Cu(Sn) samples at T=500°C, we have found a Sn 0.33Cu 0.66 p( 3 × 3 ) R30° reconstructed surface layer. By increasing T to 750°C, the tin concentration decreases up to 0.20, while the reconstruction is maintained. Atomic-resolution STM images of this phase show no rippling, but several steps. The surface lattice parameters are 0.47±0.02 and 0.51±0.02 nm, respectively, along and across the steps.