Fig. 1. Schematic diagrams of device structure and electrical test. (a) Schematic diagram of device structure and correspondence between device and biological synapses; (b) schematic diagram of electrical test process

Fig. 2. Optical synaptic plasticity of B-B SJ synaptic devices. (a) I-V curves measured under dark, illumination (9 μW/cm²) and post-illumination conditions; (b) transition from STP to LTP at different pulse numbers; (c) PPF index of device; (d) measured learning-relearning behavior; (e) decay of EPSC under different pulse numbers (inset is relationship among degree of learning, rate of forgetting, and number of pulses)

Fig. 3. CNN model

Fig. 4. Schematic diagram of mapping of conductivity to weight and variations of conductivity and EPSC of B-B SJ devices. (a) Schematic diagram of mapping process of conductivity to weight in memristive array; (b) characteristic plot of first convolutional layer; (c) EPSCs excited by different pulse numbers (3, 6, and 10); (d) variation in conductivity for different pulse numbers (3, 6, and 10)

Fig. 5. Recognition accuracy confusion matrices and accuracy distributions of M-CNNs corresponding to different pulse numbers. (a) Confusion matrix corresponding to 3 pulses; (b) accuracies of training set and test set corresponding to 3 pulses; (c) confusion matrix corresponding to 6 pulses; (d) accuracies of training set and test set corresponding to 6 pulses; (e) confusion matrix corresponding to 10 pulses; (f) accuracies of training set and test set corresponding to 10 pulses