Diffusion of oxygen vacancies on a strained rutileTiO2(110)surface

Abstract

Based on first-principles calculations of the rutile ${\text{TiO}}_{2}(110)$ surface with different types of oxygen vacancies, a phase diagram is constructed for the energetically favorable oxygen vacancy as a function of the externally applied in-plane strain. When the strain is relatively small, the bridging oxygen vacancy (BOV) is the energetically favorable one. The pathways and the energy barriers of surface diffusion of the BOV under different external strain are studied. For the cross row diffusion of the BOV along $[1\overline{1}0]$, a concerted diffusion mechanism mediated by the in-plane oxygen vacancy is found to be energetically more favorable than the hopping diffusion. The energy barrier of the concerted diffusion along $[1\overline{1}0]$ and that of the hopping diffusion along [001] are found to decrease with increasing strain. The former decreases more dramatically than the latter when the strain is applied along $[1\overline{1}0]$, which suggests a possible way of facilitating the diffusion anisotropy.