Investigating the Electronic Properties of Oxygen Vacancies in Anatase TiO2: An ab initio Study

Metal oxide dielectrics are known as promising candidates for resistive switching or memristor applications. TiO2 has been shown to be one of the favorites for the implementation of resistive switching devices. The mobile oxygen vacancies in TiO2 are recognized as the main source of resistive switching behavior. Therefore, the investigation of atomic scale properties of oxygen vacancies is of crucial importance for the description of microscopic phenomena leading to the resistive switching behavior. In the present work we employed standard DFT within the GGA approximation as well as GGA+U correction to investigate the electronic properties of oxygen vacancies in anatase phase of TiO2. We show that the Hubbard-like term (U) is essential for the correct description of the electronic properties. The defect formation energies at different charged states and the charge transition levels are calculated for different values of U-term. It has been shown that a value of U=3.5 eV is the best choice to obtain reasonable results for the band gap as well as the position of induced defect levels, at same time. Moreover, we show that the q=+2 charged state is the energetically most favorable state for the oxygen vacancy in TiO2.