The Effect of step geometry in copper oxidation by hyperthermal O molecular beam

Okada, Michio*; Vattuone, L.*; Rocca, M.*; Teraoka, Yuden

Steps are known to be often the active sites for the dissociation of O molecules since they provide paths for subsurface migration and oxygen incorporation. In order to unravel the effect of their morphology on the oxidation of Cu surfaces we present a detailed investigation of the O interaction with Cu(511) and compare it with the results for Cu(410). As for Cu(410) we find that CuO formation gradually starts above half a monolayer oxygen coverage and that the ignition of oxidation can be lowered to room temperature by dosing O via a supersonic molecular beam at hyperthermal energy. The oxidation rate for Cu(511) comes out to be lower than for Cu(410) at normal incidence, about the same when the O molecules impinge towards the ascending step rise, but higher when they hit the surface along trajectories even slightly inclined towards the descending step rise. These findings can be rationalized by a collision induced absorption mechanism.