Atomic Origin for Hydrogenation Promoted Bulk Oxygen Vacancies Removal in Vanadium Dioxide.

Oxygen vacancies (V), a common type of point defect in metal oxides materials, play important roles in the physical and chemical properties. To obtain stoichiometric oxide crystal, the pre-existing V is always removed via careful post-annealing treatment at high temperature in an air or oxygen atmosphere. However, the annealing conditions are difficult to control, and the removal of V in the bulk phase is restrained because of the high energy barrier of V migration. Here, we selected VO crystal film as the model system and developed an alternative annealing treatment aided by controllable hydrogen doping, which can realize effective removal of V defects in the VO crystal at a lower temperature. This finding is attributed to the hydrogenation accelerated oxygen vacancies recovery in the VO crystal. Theoretical calculations revealed that the H-doping-induced electrons are prone to accumulate around the oxygen defects in the VO film, which facilitates the diffusion of V and thus makes it easier to be removed. The methodology is expected to be applied to other metal oxides for oxygen-related point defects control.