Metal interdiffusion enhanced WOx/CuOx heterojunction optoelectronic memristive synapses for face recognition application

Annealing improves the switching and synaptic performance of ITO/WOx/CuOx/ITO transparent devices. The device has low SET and RESET voltages, stable and robust AC endurance of up to 106 cycles, and can retain the states for more than 104 s. The device demonstrates synaptic capabilities by emulating neural functions under both electrical and light stimuli. The behaviors including long-term potentiation/depression, paired-pulse facilitation, spike-timing-dependent plasticity, and fully tunable relaxation time of short-term memory, mimicking the temporal dynamics of the biological neuron, are declared. A convolutional neural network operation is conducted by exploiting the synaptic functions of the device. The high accuracy of 96.67% with high noise tolerance (close to an ideal synapse) can be achieved. Material analyses are conducted, and switching/synaptic mechanisms are proposed to explain such phenomena.