Anion-migration-induced bipolar resistance switching in electrochemically deposited TiO_x films

TiO_x films were electrochemically deposited on TiN and Pt electrodes with a subsequent annealing under N₂ or O₂ ambient. The resistive switching characteristics of such TiO_x films were investigated. The electrodeposited TiO_x films showed bipolar resistive switching and the operation voltages such as electroforming voltage, and reset/set voltages showed a dependence on the annealing ambient, displaying higher operation voltages for the annealing under O₂ than for the annealing under N₂. The compositions of the different chemical states of species in TiO_x films were observed to be modulated by the condition of electrochemical deposition and the subsequent annealing. The TiO_x films annealed under the O₂ ambient showed a less concentration of nonlattice oxygen ions than under N₂ ambient. The reduction of nonlattice oxygen for annealing under O₂ was accompanied by the increase of Ti³⁺ in TiO_x films and the increased reset/set voltages. It was concluded that the bipolar resistive switching of the electrochemically deposited Ti O_x film was strongly related to the nonlattice oxygen anions in the films.