Oxidation of the titanium(0001) surface: diffusion processes of oxygen from DFT

Abstract

The initial oxidation process of the Ti(0001) surface is investigated based on the diffusion of oxygen with a potential barrier by first-principles methods. The results show that oxygen molecules can dissociate freely at the Ti surface without an energy barrier and oxygen atoms are chemisorbed on the face-centered cubic (FCC) site of the surface. At low oxygen coverage on the surface, the nearest-neighbor oxygen can assist the diffusion of oxygen from the surface into the sublayer, due to the decrease in the energy barrier. Based on the analysis of the adsorption energy and diffusion barrier, the double-layer model of oxygen adsorption is proposed. With this model, the change in work function is analyzed by following the increase in adsorbed oxygen from 0 to 200%, and is consistent with the experimental results.