The Study Of Resistive Switching Memory Devices Based On TiO₂ Thin Film

In recent years, resistive random access memory have generated broad interest among academia and industry researchers due to its simple structure, high operation speed and low operation voltage. The resistive switching memories are being developed as alternatives to current technologies such as Flash memories. Though the resistive switching has been reported in many metal oxides, the switching mechanism is still unclear and drawing a matter of debate. Thus, it is of great significance to explore the physical mechanism of resistive switching. Our work focus on TiO2 based resistive switching memory device, both the metal cation and oxygen anion migration induced resistive switching were studied. Details of the work are as follows:First, the Ag/TiO2/Pt memory device shows reproductive bipolar switching behaviors. The influence of film thickness on the forming voltage has been studied. In order to understanding formation and rupture process of conductive filaments, the set and reset voltage were investigated as a function of voltage sweeping rates. Multilevel storage has been comprehensively explored in a single device via tuning the compliance current and reset voltage.Second, for the Ag/TiO2/Pt memory device, the forming process with relative large voltage is usually needed. Meanwhile, there is a large cycle-to-cycle variance in switching due to the stochastic nature of conductive filaments. To overcome these drawbacks, in this work, the TiO2 switching layer with nanopores has been synthesized by annealing TiN thin film. The ready-made filament through the nanopores can eliminate the forming process. Such nanopores TiO2 based memory device shows good switching behavior and fast write/erase whthin tens of nanosecond under 1V pulse.Third, the memory device based on the migration of oxygen ions has been prepared by Atomic Layer Deposition(ALD) of TiO2 thin film. The electric characteristic of the memory device has been studied with Pt and Al as the electrode. The device exhibits reproductive switching behavior only with the Al electrode. Further study reveals that the formed AlOx layer between Al electrode and TiO2 film is responsible for the improvement of resistive switching stability.