Multiscale simulation on electromigration of the oxygen vacancies in metal oxides

The energetics and dynamics of electromigration of the oxygen vacancy is investigated with first-principles calculations and kinetic Monte Carlo methods. To simulate the charged oxygen vacancy under external fields within the first-principles approach, we introduce a slab model with electron-accepting dopants in the surface. The analysis of the density of states confirms that the oxygen vacancies are positively charged. When the external field is applied, the total energy of the slab linearly changes with respect to the position of the charged vacancy in the field direction, which allows for probing local permittivity around the vacancy site. The activation energy of vacancy migration is lowered along the field direction in a manner that the charge state of the vacancy is maintained along the migration path. Kinetic Monte Carlo simulations based on the first-principles inputs are also carried out and it is shown that the high-temperature condition is important for the fast redistribution of charged vacancies.