Simulation of the characteristics of STDP and PPF in biological synapses. (a) Schematic illustration of the structure of biological synapses. (b) The relationship between the pulse number and the resistance of the device. Applying a negative/positive pulse to the device will cause a decrease/increase in resistance, which represents the modulation of synaptic weight owing to enhancing or suppressing the pulses. (c) Schematic diagram of the pulse waveforms applied to the device for STDP simulation. (d) Measured STDP characteristics of Ag/WSe2
QDs/LSMO/STO device, the green lines are the curves fitted by Equation (5
). (e, f) Measured PPF characteristics of Ag/WSe2
QDs/LSMO/STO device, (e) and (f) are the test results after applying positive and negative voltage pulses, respectively.