Reliable and Low-Power Multilevel Resistive Switching in TiO Nanorod Arrays Structured with a TiO Seed Layer.

The electrical performance of TiO nanorod array (NRA)-based resistive switching memory devices is examined in this paper. The formation of a seed layer on the fluorine-doped tin oxide (FTO) glass substrate after treatment in TiCl solution, before the growth of TiO NRAs on the FTO substrate via a hydrothermal process, is shown to significantly improve the resistive switching performance of the resulting TiO NRA-based device. As fabricated, the Al/TiO NRA/TiO layer/FTO device displayed electroforming-free bipolar resistive switching behavior while maintaining a stable ON/OFF ratio for more than 500 direct sweeping cycles over a retention period of 3 × 10 s. Meanwhile, the programming current as low as ∼10 A and 10 A for low resistance state and high resistance state respectively makes the fabricated devices suitable for low-power memristor applications. The TiO precursor seed layer not only promotes the uniform and preferred growth of TiO nanorods on the FTO substrate but also functions as an additional source layer of trap centers due to its oxygen-deficient composition. Our data suggest that the primary conduction mechanism in these devices arises from trap-mediated space-charge-limited current (SCLC). Multilevel memory performance in this new device is achieved by varying the SET voltage. The origin of this effect is also discussed.