Unravelling the Role of Steps in Cu2O Formation via Hyperthermal O2 Adsorption at Cu(410)

Abstract

We studied the oxidation of Cu(410) using high-resolution electron energy loss spectroscopy and X-ray photoemission spectroscopy performed with synchrotron radiation. Cu2O formation starts above half a monolayer oxygen coverage, and the oxidation rate is larger than for the parent low Miller index Cu(100) surface. Open steps favor therefore the process by opening pathways for subsurface migration and oxygen incorporation. Oxidation occurs only above 500 K when dosing O2 by backfilling, but the ignition temperature can be lowered to room temperature by dosing O2 via a supersonic molecular beam at hyperthermal energy indicating the opening of a different pathway. The oxidation rate is maximal at normal incidence; at grazing incidence, it is higher when O2 impinges nearly normal to the (100) nanofacets than when it hits the surface close to the normal to the step rises. A collision induced absorption mechanism can explain the experimental findings.