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 studi ed 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 (10x2)-O structure with high lo cal oxygen coverage. Initially, kink atoms are detached from the steps and diffuse over the surface, most probably as Rh-O units, as inferred by compa rison to x-ray photoelectron spectroscopy (XPS) data, until they condense i n zigzag structures characteristic for the (2x2)p2mg-O structure (0.5 ML). At oxygen doses above 0.12 L, missing rows begin to be dug along the [1 (1) over bar0] direction into the steps, detaching further Rh atoms. The recon struction proceeds as a missing/added row reconstruction. With ongoing surf ace reconstruction, a second reconstruction mechanism of local nature sets in: Rh atoms start to be ejected out of the terraces and condense at the en ds of the so formed troughs. Dosing further oxygen on the (2x2)p2mg-O struc ture leads to the formation of the strained (10x2)-O structure. The ejectio n of two of every 10 Rh atoms proceeds only if the Rh rows are not neighbor ed by troughs. (C) 2001 American Institute of Physics.