Oxygen-vacancy mediated adsorption and reactions of molecular oxygen on the ZnO(10(1)over-bar0) surface

We present first-principles total-energy calculations of adsorption and reaction of molecular oxygen on the ZnO(10 (1) over bar0) surface. We find that, on stoichiometric ZnO(10 (1) over bar0) surfaces, the adsorption is fully molecular with a small adsorption energy and the dissociation is energetically unfavorable. On a partially reduced ZnO(10 (1) over bar0) surface, the dissociative adsorption is energetically preferred, with one of the resulting oxygen atoms filling the original oxygen vacancy, while the other is in between two neighboring Zn atoms, forming a bridging oxygen adatom. This bridging oxygen may diffuse along the Zn-O dimer row and capture and fill another oxygen vacancy. The dissociative adsorption influences the electronic properties of the ZnO(10 (1) over bar0) surface.