Graphene-In₂Se₃ van der Waals Heterojunction Neuristor for Optical In-Memory Bimodal Operation

Functional diversification at the single-device level has become essential for emerging optical neural network (ONN) development. Stable ferroelectricity harnessed with strong light sensitivity in α-In₂Se₃ holds great potential for developing ultrathin neuromorphic devices. Herein, we demonstrated an all-2D van der Waals heterostructure-based programmable synaptic field effect transistor (FET) utilizing a ferroelectric α-In₂Se₃ nanosheet and monolayer graphene. The devices exhibited reconfigurable, multilevel nonvolatile memory (NVM) states, which can be successively modulated by multiple dual-mode (optical and electrical) stimuli and thereby used to realize energy-efficient, heterosynaptic functionalities in a biorealistic fashion. Furthermore, under light illumination, the prototypical device can toggle between volatile (photodetector) and nonvolatile optical random-access memory (ORAM) logic operation, depending upon the ferroelectric-dipole induced band adjustment. Finally, plasticity modulation from short-term to prominent long-term characteristics over a wide dynamic range was demonstrated. The inherent operation mechanism owing to the switchable polarization-induced electronic band alignment and bidirectional barrier height modulation at the heterointerface was revealed by conjugated electronic transport and Kelvin-probe force microscopy (KPFM) measurements. Overall, robust (opto)electronic weight controllability for integrated in-sensor and in-memory logic processors and multibit ORAM systems was readily accomplished by the synergistic ferrophotonic heterostructure properties. Our presented results facilitate the technological implementation of versatile all-2D heterosynapses for next-generation perception, optoelectronic logic systems, and Internet-of-Things (IoT) entities.