Dynamics of the O induced reconstruction of the Rh(110) surface: A scanning tunnelling microscopy study

The oxygen adsorption on the unreconstructed Rh(110) surface has been studied by scanning tunnelling microscopy (STM), by imaging the evolution of the surface reconstruction in situ during oxygen uptake at 390 K. The dynamics terminate with the formation of a strained (10×2)–O structure with high local oxygen coverage. Initially, kink atoms are detached from the steps and diffuse over the surface, most probably as Rh–O units, as inferred by comparison to x-ray photoelectron spectroscopy (XPS) data, until they condense in zigzag structures characteristic for the (2×2)p2mg–O structure (0.5 ML). At oxygen doses above 0.12 L, missing rows begin to be dug along the [11̄0] direction into the steps, detaching further Rh atoms. The reconstruction proceeds as a missing/added row reconstruction. With ongoing surface reconstruction, a second reconstruction mechanism of local nature sets in: Rh atoms start to be ejected out of the terraces and condense at the ends of the so formed troughs. Dosing further oxygen on the (2×2)p2mg–O structure leads to the formation of the strained (10×2)–O structure. The ejection of two of every 10 Rh atoms proceeds only if the Rh rows are not neighbored by troughs.