Resistive switching characteristics of TiO2 films prepared by DC magnetron sputtering: Effects of nitrogen composition and phase structure

We investigate the resistive switching characteristics of TiO2 films deposited by DC magnetron sputter deposition using a metallic Ti target in different ratios of argon (Ar), oxygen (O2), and nitrous oxide (N2O) atmosphere. The resistive switching device is fabricated with a Pt/TiO2/ITO structure. It is revealed that the resistive switching characteristics of TiO2 films are strongly affected by the gas atmosphere and the substrate temperature. Using N2O as the N source to prepare N-doped TiO2 films is demonstrated to have the advantage of low temperature and no subsequent heat treatment, and the prepared TiO2 exhibits a high potential for resistive memory applications. The XRD measurement suggests that the crystal structure of the N-doped TiO2 films exhibits a rutile (110) peak when the substrate temperature is below 300 °C. When the substrate temperature is above 350 °C, both the rutile phase with a typical (110) peak and the anatase phase with a typical (101) peak will be observed. The reliability of the memory effects is evaluated by performing a switching cycling test. The retention of the high-resistance state (HRS) and the low-resistance state (LRS) for all TiO2 devices deposited at various substrate temperatures can be held over 104 s. Furthermore, the ratio of HRS/LRS for the device deposited at 300 °C temperature can approach >4 orders and exhibit long switch stability and good durability in atmosphere. All of the devices displayed dominant space charge limiting current conduction mechanisms. The optimal number of oxygen vacancies in the N2O-doped TiO2 film is beneficial for improving the resistive random-access memory performance, and the rutile phase is better than the anatase phase for resistive memory potential applications.