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

Abstract

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.