Optimization of the Cycle Numbers of TiO₂ Resistive Random-Access Memory Devices by Annealing

Resistance switching (RS) devices that are based on titanium dioxide (TiO 2 ) nanomaterials have recently attracted substantial research interest because of their simple preparation technology and potential applications in the applications of memory devices. In this paper, the RS characteristics of TiO 2 -based memristors were regulated by changing the crystal structure of the TiO 2 film. Resistive switching memory, consisting of Ag/amorphous TiO 2 /Ti fabricated by anodic oxidation, exhibited poor cycling stability. Annealing was applied to the anodized sample over the temperature range of 230–680 °C, and the structure of TiO 2 was investigated throughout the process. Amorphous TiO 2 transformed into the anatase phase as the annealing temperature was increased to 280 °C and the stable cycle number of the device peaked at 51. By annealing at >450 °C, TiO 2 was gradually transformed into the rutile phase, and the stable cycle number of the device decreased to 7. X-ray photoelectron spectroscopy confirmed that the concentration of oxygen vacancies in rutile TiO 2 decreased with increasing temperature compared with that in anatase TiO 2, resulting in the declining performance of the device. This work presents a low-cost annealing process to prepare stable anatase TiO 2 -based memristors, which will promote the industrialization of the devices for nonvolatile memory applications in the future.