Fig. 2

a Schematic diagram of Pt/HfO₂/Al₂O₃/TaN memristive device in electrical measurement configuration, which shows that the external voltage is applied to the Pt top electrode with the TaN bottom electrode electrically grounded. b I–V curves of an electroforming process (blue) and reset process (red). The arrows and numbers represent voltage sweep directions and sequences, respectively. c Typical bipolar I–V characteristics of 100 consecutive cycles, where green arrows indicate the set and reset directions. d DC endurance test results over 1000 cycles; the values of ON-state and OFF-state resistances were read at ± 0.2 V under ambient conditions. e Data retention characteristics of ON state and OFF state under a constant voltage stress of 0.2 V for 10⁴ s at room temperature. f Statistical distribution analyses of set and reset voltages for the 100 switching cycles