A kinetic Monte Carlo investigation was made of an atomistic model for 3-dimensional structural configurations of TiO2 memristors; focusing on oxygen vacancy migration and interaction under an external voltage bias. Kinetic Monte Carlo methods permitted access to experimental time-scales so that the formation of well-defined vacancy filaments in thin TiO2 films could be simulated. The results showed that the electric field drove vacancy migration; and vacancy hopping-induced localized electric field played a key role in filament evolution. Using the kinetic Monte Carlo structure of the filaments at different stages of the formation process, electronic density of states were calculated using density functional theory. Filament-induced gap states were found which gave rise to a transition from insulating behavior to conducting behavior during the filament formation process. By varying kinetic Monte Carlo simulation parameters, relationships between vacancy diffusion, filament formation, and density of states in the TiO2 thin film were elucidated.

Oxygen Vacancy Filament Formation in TiO2: a Kinetic Monte Carlo Study. D.Li, M.Li, F.Zahid, J.Wang, H.Guo: Journal of Applied Physics, 2012, 112[7], 073512