Coexistence of Memristive Behaviors and Negative Capacitance Effects in Single-Crystal $\hbox {TiO}_{2}$ Thin-Film-Based Devices

Pt/TiO₂/Nb:SrTiO₃/Pt devices show pronounced bipolar multilevel resistive switching behaviors and negative capacitance effects. The active layer TiO₂ was grown on Nb-doped SrTiO₃ by molecular beam epitaxial technology. With the aid of forward or reverse bias, the devices can be switched to insulating or different conductive states. The devices show prominent negative capacitance effects strongly depending on the initial state of high or low resistance. The observed results may be attributed to oxygen vacancy´s migration-induced conductive state change of the TiO₂ thin films and to the corresponding variation of charge lagging behind that of voltage.