Measured features of TiO
-based ReRAM devices. (a) SEM image of a crossbar-type prototype based on TiO2 cell with an active area of 5 × 5 μm2. (b) Measured I-V characteristics showing a typical unipolar switching signature. Inset: schematic view of the measured cell. (c, d) Resistance evolution results of two practical devices with identical initial resistive states at room temperature. (e) Pulse-induced programming and evaluating scheme, where Vset and Vread represent resistance programming and evaluating pulses, respectively.