Electric-induced resistance switching (EIRS) effect based on transition metal (TM) oxides, such as perovskite manganites (Pr1-xCaxMnO3, La1-xCaxMnO3) and binary oxides (NiO, TiO2 and CoO) etc, has attracted great interest for potential applications in next generation nonvolatile memory known as resistance random access memory (RRAM). Compared with other nonvolatile memories, RRAM has several advantages, such as fast erasing times, high storage densities, and low operating consumption. Up to date, the switching mechanism, property improvement and new materials exploitation are still the hotspots in RRAM research.
In this report, the main results of resistance switching of two kinds of TM oxides including La0.7Ca0.3MnO3 and TiO2 were presented. Based on the I-V characteristics, the field-direction dependence of resistance switching (RS) behavior, and the conduction process analysis, the EIRS mechanisms were studied in detail. For the La0.7Ca0.3MnO3 film, the EIRS mechanism was related to the carrier injected space charge limited current (SCLC) conduction controlled by the traps existing at the interface between top electrode and La0.7Ca0.3MnO3 film. The RS behavior is produced by the trapping/detrapping process of carriers under different voltages. For the TiO2 film, both unipolar and bipolar RS behavior can be obtained in our experiments. The interface controlled filamentary mechanism was proposed to explain the unipolar EIRS in nanocrystalline TiO2 thin films, while the bipolar RS behavior may be related to the charge trapping or detrapping effect. In addition, it was confirmed that the I-V sweeps in vacuum environment, the applying of asymmetry pulse pairs and the oxygen annealing of films can improve the endurance of the EIRS devices. Our researches will provide some meaningful clues to understanding the EIRS mechanism and some useful pathways for the development of RRAM devices.