Ferroelectric Switching Behavior in Two-Dimensional Semiconductor α-In₂Se₃ for Nonvolatile Memory

Ferroelectric memristors, a type of nonvolatile resistive switching memory, have enormous potential in applications, including information storage and neuromorphic computing. The recent focus on two-dimensional (2D) ferroelectrics highlights their significance as a promising platform for the next generation of functional electronic devices. Here, we report ferroelectricity in exfoliated 2D alpha-In2Se3 flakes through piezoelectric force microscopy and transport measurement. An out-of-plane ferroelectricity is directly characterized by a box-in-box ferroelectric domain pattern. In-plane ferroelectricity is also proved in alpha-In2Se3 planar ferroelectric devices by the large hysteresis loop, while the out-of-plane ferroelectricity is further observed by the electric field gating effect. Remarkably, this 2D alpha-In2Se3-based ferroelectric semiconductor field-effect transistor exhibits a high on/off ratio as well as good cyclability. Additionally, few-layer graphene/alpha-In2Se3/few-layer graphene ferroelectric heterojunctions are also fabricated, which showcase the potential of alpha-In2Se3 for vertical ferroelectric memristors.