Oxygen vacancies are among the most abundant native point defects in ZnO and are major actors in many surface reactions important for catalysis and gas sensing. We have explored the electronic character of such F centers at the surface and in the bulk. We have also explored how dopants and temperature affect the nature of the oxygen vacancies and the cost to create them. The main methods used in this work are static first-principles calculations and ab initio molecular dynamics simulations.
We find that the electron density associated with the defect state in reduced ZnO shows partial localization of electrons in the F-center but also on its nearest oxygen neighbors. Following the introduction of dopant atoms, major changes in the local electronic structure connected to the oxygen vacancy were found. Indeed, Li-doping is effectively compensating the F-center impurity state and lowers the oxygen vacancy formation energy. This decrease in vacancy formation energy is found to be strongly dependent of the dopant position. |