Truly Electroforming-Free Memristor Based on TiO₂-CoO Phase-Separated Oxides with Extremely High Uniformity and Low Power Consumption

Oxide-based memristor devices are being extensively studied as one of the most promising technologies for next generation nonvolatile memory and neuromorphic computing. However, the switching process of such devices relying on the formation and rupture of conductive filaments has not been easily controlled, and thus induces large cycle-to-cycle and device-to-device variations in resistive switching, which hinders the development of high-performance memristors. High-performance memristors that meet the requirements for truly electroforming-free, highly uniform, and low-power switching are yet to be developed. Here, a phase-separated oxide memristor is demonstrated based on a spontaneous phase separation process to form amorphous TiO₂ switching medium distributed among the crystalline CoO grains. The confinement of conductive filaments into the intergrain amorphous oxide phase effectively minimizes the stochasticity of filament formation and rupture, resulting in drastically enhanced switching uniformity. The designed microstructure also facilitates filament formation and dissolution during switching processes and leads to truly electroforming-free switching and low switching power (simultaneous low switching voltage 0.4 V and low current 2.5 µA).