Self-Limited Growth of a Thin Oxide Layer on Rh(111)

The oxidation of the Rh(111) surface at oxygen pressures from ${10}^{\ensuremath{-}10}\text{ }\mathrm{mbar}$ to 0.5 bar and temperatures between 300 and 900 K has been studied on the atomic scale using a multimethod approach of experimental and theoretical techniques. Oxidation starts at the steps, resulting in a trilayer O-Rh-O surface oxide which, although not thermodynamically stable, prevents further oxidation at intermediate pressures. A thick corundum like ${\mathrm{Rh}}_{2}{\mathrm{O}}_{3}$ bulk oxide is formed only at significantly higher pressures and temperatures.