STM and SPA-LEED studies of O-induced structures on Rh(100) surfaces

Abstract

Oxygen adsorption on the Rh(100) surface has been studied by spot profile analysis low energy electron diffraction (SPA-LEED) and scanning tunnelling microscopy (STM). Our results show that oxygen can be reliably dosed onto the Rh(100) surface to produce distinct p(2 × 2) and c(2 × 2) phases. Additionally, the symmetry of the phase formed at saturation coverage is identified as (2 × 2)p4g rather than (2 × 2)p2gg as had been proposed previously. STM images of both the c(2 × 2) and (2 × 2)p4g phases show that the O atoms sit in alternate four-fold hollow sites. It is proposed that the difference between these two structures is a result of overall oxygen coverage. In the c(2 × 2) case we speculate that surface strain is relieved by the formation of islands, but that for the saturation coverage (2 × 2)p4g structure surface strain is reduced by the O atom burrowing into the surface, causing the characteristic clock reconstruction of the substrate Rh atoms.