Fig. 3: The refresh ability of the device.

a Evolution of the device current when cyclically working under the ion migration (blue dots) and ferroelectric polarization (red dots) mode. Red arrows mark the stages of induced ferroelectric polarizations. The inset illustrates the configuration of examinations within one cycle, including polarization, ion migration, ion relaxation and polarization, sequentially. b Evolution of the device current undergoing repeated cycles of ion migration (light blue dots, obtained utilizing 60 pulses, each including a 0.2 s set voltage at −1.5 V followed by a 0.1 s read voltage at −0.6 V.) and spontaneous relaxation (deep blue dots, obtained utilizing 60 pulses, each with a duration of 3.4 s at a voltage of 0 V, followed by a 0.1 s read voltage at −0.6 V.). The varying ferroelectric polarization states were determined via 20 pulses with a period of 3 s, where 0 V is applied for 2.8 s and −0.6 V is applied for 0.2 s (deep red dots). The subsequent ferroelectric polarization states (light blue dots) were determined by 100 pulses with a period of 0.6 s, where 0 V is applied for 0.5 s and −0.6 V is applied for 0.1 s. c The normalization of the data marked by blue dots in (b). d The dependence of the maximum current (\({I}^{60}\)) induced by the ion migration process on the corresponding initial current (\({I}_{{ferr}}\)) induced by ferroelectric polarization. e The energy band diagram of the device during ion migration process at distinct ferroelectric polarization states, where a is the distance between two adjacent, equivalent lattice sites, E is the electric field and e is charge.