Fig. 2: The vdW ferroelectric memristor device structure and the ferroionic electrical property of CuInP₂S₆.

a Schematic of the vertical heterojunction integrating the functionality of the MoS₂ / CuInP₂S₆ / MoS₂ memristor and MIS-FET. b Schematic of neurons and chemical synapses. c The energy band diagram of the device in both high resistance state (HRS) and low resistance state (LRS), depicting ferroelectric polarization mode (upper) and ion migration mode (lower), respectively. d The demonstration of the memory windows of a typical S-FE-S memristor. The red arrows indicate the current measured via applying the voltage pulse train (shown in the inset). e The LTP and LTD measured under the ferroelectric polarization working mode. Here, the 40 set (30 reset) pulses are organized into a group, with the voltage ranging from 7 V to 14.5 V (−5 V to −6.6 V) in fixed intervals of 0.5 V (−0.1 V) between distinct groups. Each pulse had a duration of 0.01 s, followed by an interval of 0.4 s with no voltage. Finally, each state was assessed as shown in Supplementary Fig. 4. f Retention characteristics of 16 distinct ferroelectric polarization states. The different states were obtained by the same excitation pulses as in (e). g I–V characteristic of the device while applying a fixed gate voltage of −4 V. The blue arrows denote the switching direction. h The LTP and LTD measured under the ion migration working mode. The bias voltage was programmed by a series of set pulses (−1.5 V, 0.2 s) followed by a series of reset ones (0.22 V, 0.4 s) and each excitation pulse is accompanied by a fixed read pulse (−0.6 V, 0.1 s). i The evolution trend of current with time in different states under a fixed read pulse sequence. Here, distinct ion migration states were achieved utilizing the same pulse pattern as in (h), but with varying numbers. The inset is the replotted segments within the range of 45 s.