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A novel strategy based on defect engineering is proposed for high-performance multibit data storage in oxide-based resistive random access memory (RRAM). Key innovations are: 1) material-oriented cell engineering for desired modification of physical locations of generated oxygen vacancies in resistive switching layer; and 2) operation scheme to control the amount of oxygen vacancy generated in the conducting filament regions during switching. Proper doping approach is applied to suppress the formation of oxygen vacancy clusters due to the avalanching effect in the forming and set processes. Gradual resistive switching process is observed in the devices with proper doping at the proper switching operation modes. Multilevels of resistance states are measured by the optimized dc or ac switching mode. Excellent memory performance with four-level data storage (good resistance uniformity under pulse switching, retention >10 4 s at 150°C, and endurance >10 6 cycles) is successfully demonstrated in hafnium oxide-based RRAM devices, indicating the viability of the proposed engineering design strategy. The proposed methodology helps to understand the mechanism of multilevel switching and provides guidelines for the design of high-performance multibit resistive switching memory devices.
Gao et al. (Thu,) studied this question.