Controlled hydrothermal growth of uniform rutile TiO 2 nanorod arrays for memristive applications

Abstract

Synthesis of highly uniform rutile TiO 2 nanorod arrays has long been a priority for fabricating the high-performance memristors, given its great potential as active-layer materials in memristive devices. Herein, a controllable hydrothermal synthesis of highly uniform rutile TiO 2 nanorod arrays on fluorine-doped tin oxide (FTO) substrates is presented. Through systematic investigations, it is revealed that the highly uniform rutile TiO 2 nanorod arrays are obtained via a 3-hour hydrothermal synthesis at 160 °C on vertical FTO substrates, postannealing at 450 °C for 1 hour, followed by 25-minute ultraviolet (UV) irradiation. The obtained TiO 2 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/TiO 2 /FTO memristive devices demonstrate remarkable resistive switching characteristics: (i) the ratio of high resistance state (HRS) and 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 TiO 2 nanorod array films, demonstrating their promising applications in high-performance memristive devices.