STM AND SPA-LEED STUDIES OF O-INDUCED STRUCTURES ON RH(100) SURFACES

Oxygen adsorption on the Rh(100) surface has been studied by spot prof ile analysis low energy electron diffraction (SPA-LEED) and scanning t unnelling microscopy (STM). Our results show that oxygen can be reliab ly dosed onto the Rh(100) surface to produce distinct p(2 x 2) and c(2 x 2) phases. Additionally, the symmetry of the phase formed at satura tion coverage is identified as (2 x 2)p4g rather than (2 x 2)p2gg as h ad been proposed previously. STM images of both the c(2 x 2) and (2 x 2)p4g phases show that the O atoms sit in alternate four-fold hollow s ites. It is proposed that the difference between these two structures is a result of overall oxygen coverage, In the c(2 x 2) case we specul ate that surface strain is relieved by the formation of islands, but t hat for the saturation coverage (2 x 2)p4g structure surface strain is reduced by the O atom burrowing into the surface, causing the charact eristic clock reconstruction of the substrate Ph atoms.