Oxygen vacancy filament formation in TiO2: A kinetic Monte Carlo study

We report a kinetic Monte Carlo (kMC) investigation of an atomistic model for 3-dimensional structural configurations of TiO2 memristor, focusing on the oxygen vacancy migration and interaction under an external voltage bias. kMC allows the access of experimental time scales so that the formation of well defined vacancy filaments in thin TiO2 films can be simulated. The results show that the electric field drives vacancy migration; and vacancy hopping-induced localized electric field plays a key role for the filament evolution. Using the kMC structure of the filaments at different stages of the formation process, electronic density of states (DOS) are calculated by density functional theory. Filament induced gap states are found which gives rise to a transition from insulating behavior to conducting behavior during the filament formation process. By varying kMC simulations parameters, relations between vacancy diffusion, filament formation, and DOS in the TiO2 thin film are elucidated. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757584]