Controlled hydrothermal growth of uniform rutile TiO₂ nanorod arrays for memristive applications

Synthesis of highly uniform rutile TiO₂ nanorod arrays has long been a priority for fabricating high-performance memristors, given their great potential as active-layer materials in memristive devices. Herein, a controllable hydrothermal synthesis of highly uniform rutile TiO₂ nanorod arrays on fluorine-doped tin oxide (FTO) substrates is presented. Through systematic investigations, it is revealed that highly uniform rutile TiO₂ nanorod arrays are obtained via a 3 hours hydrothermal synthesis at 160 °C on vertical FTO substrates, followed by post-annealing at 450 °C for 1 hour and 25-minute ultraviolet (UV) irradiation. The obtained TiO₂ nanorod arrays exhibit excellent substrate adhesion and pinhole-free morphology, with well-defined nanorod dimensions (an average diameter of 171 nm and a length of 2.44 µm) and high crystallinity (an average crystallite size of 16.66 nm). Using such nanorod arrays as the active layers, the Ag/TiO₂/FTO memristive devices demonstrate remarkable resistive switching characteristics: (i) the ratio of the high resistance state (HRS) to the low resistance state (LRS) reaches 17.7, and (ii) the retention time is predicted to be more than 10 years. Current-voltage analysis indicates that the resistive switching behavior follows a synergistic combination of ohmic conduction and space-charge-limited current (SCLC) mechanisms. The current work offers valuable guidelines for structure-property optimization in highly uniform rutile TiO₂ nanorod array films, demonstrating their promising applications in high-performance memristive devices.