Customized binary and multi-level HfO-based memristors tuned by oxidation conditions.

The memristor is a promising candidate for the next generation non-volatile memory, especially based on HfO, given its compatibility with advanced CMOS technologies. Although various resistive transitions were reported independently, customized binary and multi-level memristors in unified HfO material have not been studied. Here we report Pt/HfO/Ti memristors with double memristive modes, forming-free and low operation voltage, which were tuned by oxidation conditions of HfO films. As O/Hf ratios of HfO films increase, the forming voltages, SET voltages, and R/R windows increase regularly while their resistive transitions undergo from gradually to sharply in I/V sweep. Two memristors with typical resistive transitions were studied to customize binary and multi-level memristive modes, respectively. For binary mode, high-speed switching with 10 pulses (10 ns) and retention test at 85 °C (>10 s) were achieved. For multi-level mode, the 12-levels stable resistance states were confirmed by ongoing multi-window switching (ranging from 10 ns to 1 μs and completing 10 cycles of each pulse). Our customized binary and multi-level HfO-based memristors show high-speed switching, multi-level storage and excellent stability, which can be separately applied to logic computing and neuromorphic computing, further suitable for in-memory computing chip when deposition atmosphere may be fine-tuned.