First principles modeling of charged oxygen vacancy filaments in reduced TiO2–implications to the operation of non-volatile memory devices

First principles density functional theory calculations were employed to study the band structure of reduced rutile TiO2 and the implications of oxygen vacancy charge states on the switching mechanisms observed in resistance change random access memory devices. The formation of conductive paths in TiO2 composed of oxygen vacancy filaments were investigated using the LDA+Ud+Up method to calculate the band-structure, electron localization functions, partial charge densities of defect states and the Bader charge decompositions. The thermodynamic stability of charged oxygen vacancies on resistive switching are discussed based on the defect formation energies and a resistive switching mechanism is proposed based on models of filament formation and rupture.