Based on first-principles calculations of the rutile TiO2(110) surface with different types of oxygen vacancies, a phase diagram was constructed for the energetically favourable oxygen vacancy as a function of the externally applied in-plane strain. When the strain was relatively small, the bridging oxygen vacancy was the energetically favourable one. The pathways and the energy barriers of surface diffusion of the bridging oxygen vacancy under different external strain were studied. For the cross row diffusion of the bridging oxygen vacancy along [1¯10], a concerted diffusion mechanism mediated by the in-plane oxygen vacancy was found to be energetically more favourable than the hopping diffusion. The energy barrier of the concerted diffusion along [1¯10] and that of the hopping diffusion along [001] were found to decrease with increasing strain. The former decreases more dramatically than the latter when the strain was applied along [1¯10], which suggested a possible way of facilitating the diffusion anisotropy.

Diffusion of Oxygen Vacancies on a Strained Rutile TiO2(110) Surface. Z.W.Wang, D.J.Shu, M.Wang, N.B.Ming: Physical Review B, 2010, 82[16], 165309