Oxygen adsorption at heterophase boundaries of the oxygenated Cu(110)

Abstract

Many metal-oxygen systems involve progressive stages of oxygen chemisorption induced surface phase transition and restructuring that result in the formation of heterophase boundaries within the oxygen chemisorbed layer. Using the density functional theory calculations, we investigated the effect of such heterophase boundaries formed by the (2 × 1)-O → c(6 × 2)-O phase transition on Cu(110) on the onset of bulk oxidation. Upon the increased oxygen coverage, we show that some (2 × 1)/(6 × 2) boundaries allow for further propagation of the (2 × 1)/(6 × 2) phase boundary while the other boundaries promote subsurface oxygen adsorption that results in the formation of Cu2O-like tetrahedrons. By comparing the surface height of the Cu atoms within the heterophase boundary area, we show that the boundaries with a larger surface elevation of the Cu atoms are prone to form Cu2O-like tetrahedrons by subsurface oxygen occupancy. These results indicate that the presence of the two-phase boundaries formed by the surface phase transition in the oxygen chemisorbed layer facilitates the inward diffusion of oxygen atoms and thus initiates the onset of bulk oxidation.