Fig. 4
a Typical bipolar I–V characteristics and b comparison of ON/OFF resistance ratios of the Pt/HfO2/Al2O3/TaN memristive device under different reset-stop voltages, i.e., + 2.0 V and + 3.0 V, with fixed set voltage of − 5 V. c, d Schematic illustration of switching mechanism of OFF state at different reset-stop voltages (2.0 V and 3.0 V) for the prepared Pt/HfO2/Al2O3/TaN memristive device