Ternary Synaptic Plasticity Arising from Memdiode Behavior of TiO_x Single Nanowires

Electric field‐induced resistive switching (RS) effect has been widely explored as a novel nonvolatile memory over the past few years. Recently, the RS behavior with continuous transition has received considerable attention for its promising prospect in neuromorphic simulation. Here, the switching characteristics of a planar‐structured TiO_x single nanowire device are systematically investigated. It exhibits a strongly history‐dependent rectifying behavior that is defined as a “memdiode.” It is further demonstrated that a ternary synaptic plasticity could be realized in such TiO_x nanowire device, characterized by the resistance and photocurrent response. For a given state of the memdiode, a conjugated memristive characteristic and a distinct photocurrent can be simultaneously obtained, resulting in a synchronous implementation of various Hebbian plasticities with the same temporal order of spikes. These intriguing properties of TiO_x memdiode provide a feasible way toward the designing of multifunctional electronic synapses as well as programmable artificial neural network.