Study On The Preparation Process And Metal-insulation-transformation Properties Of Titanium Dioxide

In recent years, new non-volatile memory, for instance RRAM, has attracted wide attention in next-generation storage devices application. The resistive random access memory based on binary transition metal oxides has better performance on storage capacity, such as low power consumption, small size, simple memory cell, faster read-write capacity, better compatibility with CMOS process.In this paper, we mainly studied the resistive switching characteristics of TiO₂ thin film. We used ultra-high vacuum multifunctional magnetron sputtering system to prepare TiO₂ thin film. Morphology, microstructure and resistive switching properties of TiO₂ thin film were characterized by atomic force microscope (AFM), X-ray diffraction (XRD), semiconductor parameter analyzer (SPA), respectively.Firstly, we studied effects of substrate temperature on the structure and the switching characteristics of TiO₂. Electrical test results showed that, with the temperature increasing from 200℃to 300℃, the fluctuation of Vreset for the samples became larger, and finally reversible resistive switching disappeared. The sample deposited at room temperature appeared stable resistive switching properties. But film deposited at 350℃comparison to RT exhibited more stable and superior resistance switching behaviors with the set and reset voltage as low as 0.58V and 0.45V, respectively.Next, we studied effects of different oxygen flow ratios on switching properties of TiO₂. Electrical tests showed that film samples at FO2%=10% performed a relatively stable resistance switching characteristics and highly repeatable characteristics of BRS and URS.Finally, the study examined effects of Cu, Ag, Al, W and Ti bottom electrode (BE) on resistive switching behavior in Cu/TiO₂/BE sandwich structure by current-voltage (I-V) measurement. Results suggested that a relative high potential barrier was formed at Cu/TiO₂ interface, and unipolar resistance switching (URS) was accompanied by SCLC and Schottky emission. At TiO₂/Ag interface, which formed a relatively low potential barrier height, only BRS characteristics were observed. For Cu/TiO₂/Al structure resistive switching behaviors was failing to be observed due to interface chemical reaction. After twice switching, Cu/TiO₂/W structure showed ohmic properties. For the Ti electrode, resistive switching was not observed because TiO phase was formed at the interface.In a word, the effects of deposition conditions on the resistance switching of TiO₂ thin film were systematically studied in this paper, and the resistance mechanisms were also conducted a preliminary exploration. The work we done had laid a foundation for the next research of resistance-change memory.