Artificial optoelectronic synapses with both electrical and light‐induced synaptic behaviors have recently been studied for applications in neuromorphic computing and artificial vision systems. However, the combination of visual perception and high‐performance information processing capabilities still faces challenges. In this work, the authors demonstrate a memristor based on 2D bismuth oxyiodide (BiOI) nanosheets that can exhibit bipolar resistive switching (RS) performance as well as electrical and light‐induced synaptic plasticity eminently suitable for low‐power optoelectronic synapses. The fabricated memristor exhibits high‐performance RS behaviors with a high ON/OFF ratio up to 105, an ultralow SET voltage of ≈0.05 V which is one order of magnitude lower than that of most reported memristors based on 2D materials, and low power consumption. Furthermore, the memristor demonstrates not only electrical voltage‐driven long‐term potentiation, depression plasticity, and paired‐pulse facilitation, but also light‐induced short‐ and long‐term plasticity. Moreover, the photonic synapse can be used to simulate the “learning experience” behaviors of human brain. Consequently, not only the memristor based on BiOI nanosheets shows ultra‐low SET voltage and low‐power consumption, but also the optoelectronic synapse provides new material and strategy to construct low‐power retina‐like vision sensors with functions of perceiving and processing information.

A memristor is a two-terminal device with nonvolatile resistive switching (RS) behaviors. Recently, memristors have been highly desirable for both fundamental research and technological applications because of their great potential in the development of high-density memory technology and neuromorphic computing. Benefiting from the unique two-dimensional (2D) layered structure and outstanding properties, 2D materials have proven to be good candidates for use in gate-tunable, highly reliable, heterojunctioncompatible, and low-power memristive devices. More intriguing, stable and reliable nonvolatile RS behaviors can be achieved in multi-and even monolayer 2D materials, which seems unlikely to be achieved in traditional oxides with thicknesses less than a few nanometers because of the leakage currents. Moreover, such two-terminal devices show a series of synaptic functionalities, suggesting applications in simulating a biological synapse in the neural network. In this review article, we summarize the recent progress in memristors based on inorganic and organic 2D materials, from the material synthesis, device structure and fabrication, and physical mechanism to some versatile memristors based on diverse 2D materials with good RS properties and memristor-based synaptic applications. The development prospects and challenges at the current stage are then highlighted, which is expected to inspire further advancements and new insights into the fields of information storage and neuromorphic computing.

Neural synapses with diverse synaptic functions of short- and long-term plasticity are highly desired for developing complex neuromorphic system. Memristor with its two terminals respectively serving as pre- and post-neurons...

Scientists have been seeking for suitable materials with nonvolatile resistive switching (RS) performance for memristive applications. Recently, nonvolatile RS behaviors have been achieved in an increasing number of two-dimensional (2D) materials. However, 2D InSe layers have not been reported to demonstrate such nonvolatile RS behaviors. Herein, we experimentally observe nonvolatile bipolar RS behaviors in 2D InSe nanosheets through controllable oxidation. In our experiments, the exfoliated InSe nanosheets annealed at the temperature of 350 °C for 2 h show typical nonvolatile bipolar RS performance with a low SET voltage of ∼0.3 V and a high ON/OFF ratio of 4.5 × 103 at the read voltage of 0.1 V. Raman and x-ray photoelectron spectroscopy characterizations confirm the partial oxidation in InSe nanosheets after annealing. The observed nonvolatile RS behaviors are owing to the formation of In2O3 and the increased insulating characteristic in the annealed InSe nanosheets. Furthermore, the fabricated memristor exhibits good retention property and endurance performance. Such annealed InSe nanosheets not only demonstrate decent RS performance but also enrich the family of 2D materials to fabricate memristors for applications in next-generation nonvolatile memory.