The Oxide Films Formed on Copper Single Crystal Surfaces in Water

Abstract

Studies of the effect of illumination on the growth of oxide films on copper single crystal surfaces immersed in water containing different amounts of dissolved oxygen reveal that, while illumination has little effect on the oxidation process when the water is in equilibrium with a 100% oxygen atmosphere, it does lower the rate of film formation when the water is in equilibrium with 1% oxygen. For both the (111) and (100) planes illumination causes a departure from the rate law observed for oxidation in the dark. At intensities of 290 µw/cm2 or higher the film formed on the (111) plane never grows beyond a limiting thickness of 100Aå. The behavior observed can be explained on the basis of a competition between growth and dissolution reactions, the dissolution reaction being promoted by illumination.