Nanoscale morphology and oxidation of ion-sputtered Rh(1Â 1Â 0) and Ru(0Â 0Â 0Â 1)

The influence of nanoscale morphology of the Rh(1 1 0) and Ru(0 0 0 1) surfaces on their oxidation by molecular oxygen has been studied by scanning tunneling microscopy (STM) and scanning photoelectron microscopy (SPEM). The STM results clearly show that after roughening by ion sputtering, these surfaces consist of step-bunching areas and almost atomically flat plateaus. For both metals SPEM measurements reveal that the step-bunching areas, consisting of narrow terraces separated by single atomic steps, oxidize more promptly than plateaus. The locally higher chemical activity of the step-bunching areas is tentatively attributed to the higher density of defects, which promotes the penetration of oxygen underneath the surface.