The Effect of step geometry in copper oxidation by hyperthermal O molecular beam; Cu(511) vs Cu(410)

超熱O分子線による銅酸化におけるステップ構造の影響; Cu(511)とCu(410)の比較

岡田 美智雄*; Vattuone, L.*; Rocca, M.*; 寺岡 有殿

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

Steps are known to be often the active sites for the dissociation of O molecules and the nucleation sites of oxide films. In order to unravel the effect of their morphology on the oxidation of Cu surfaces we present here a detailed investigation of the O interaction with Cu(511) and compare it with Cu(410). As for Cu(410) we find, by X-ray photoemission spectroscopy performed with synchrotron radiation, 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 supersonic O molecular beam. The oxidation rate of Cu(511) comes out to be lower than that of 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.