Polarization-Controlled Dual-Mode Switching in van der Waals α-In2Se3 Memristors for Multitime-Scale Reservoir Computing

Electrochemical-metallization (ECM) memristors can implement both nonvolatile memory switching and volatile threshold switching, making them attractive for neuromorphic and reservoir computing; however, the stochastic formation of metallic filaments causes variability in the threshold voltage and switching instability. Here, we report a van der Waals α-In2Se3-based ferroelectric-semiconductor ECM (FeS-ECM) memristor in which a bidirectionally polarized α-In2Se3 layer is inserted between the inert electrode and the switching layer. The out-of-plane ferroelectric polarization, programmed through a decoupled in-plane poling terminal, deterministically selects within the low-compliance operating regime between nonvolatile bipolar memory switching and volatile unipolar threshold switching within a single device, with a coefficient of variation in the set voltage of 4.7% and stable operation over more than 9000 cycles. Exploiting these two modes, a single α-In2Se3 platform exhibits both the volatile reservoir dynamics and the nonvolatile conductance modulation required for the readout weights of a physical reservoir-computing system, in which the pulse width electrically programs multiple relaxation time constants. This pulse-width multitime scale reconfigurability enables efficient temporal information processing, demonstrated through MNIST classification and chaotic time-series prediction.