Observation of bias-dependent noise sources in a TiO_x/TiO _y bipolar resistive switching frame

We report the conduction features associated with the evolution of oxygen ions (or vacancies) under bias for a TiO_x (oxygen ion-rich)/TiO _y (oxygen ion-deficient) bi-layer cell by identifying low-frequency noise sources. It is believed that a low resistance state enhances the formation of conductive filaments exchanging electrons through a nearest-neighbor hopping process, while a high resistance state (HRS) emphasizes the rupture of conductive filaments inside the insulating TiO_x layer and a reduction/oxidation reaction at the oxide interfaces. The high resolution transmission electron microscope images of as-grown and HRS cells are also discussed.