Fig. 1
Integrate-and-fire dynamics of the dynamic pseudo-memcapacitor (DPM). a Scanning electron micrograph of the plan view of the integrated DPM, and a transmission electron micrograph of the cross-section. b Charge–voltage relationship of the integrated DPM. The hysteresis loops reveal the volatile switching between the intrinsic parallel capacitor CP of the memristor and the series capacitor CS. c Schematic representation of a biological neuron generating an action potential after receiving high-frequency post-synaptic inputs. At time t1, the membrane potential did not reach the threshold so few sodium channels were open upon the arrival of the signal. As the neuron received further input stimuli, the membrane potential hit the threshold at time t2 inducing quick opening of all available sodium ion channels. The potential reached its maximum and started to decrease due to the repolarization caused by the opening of the potassium ion channel and inactivation of sodium ion channels. d The integrate-and-fire process of a DPM. At time t1′, the potential across the capacitor rose upon the input stimulus due to the nonlinear OFF state resistance of the diffusive memristor. At time t2′, the diffusive memristor was switched ON by the pre-synaptic spike to fully charge the capacitor, which replicated the upswing of membrane potential due to the opening of all sodium ion channels at t2 of c. At time t3′, the pre-synaptic input was low. The memristor was first switched OFF and then switched ON again with opposite bias, which quickly discharged the capacitor and brought the membrane potential back to its resting value, similar to the repolarization caused by the opening of potassium ion channels. e Schematic of the neuro-transistor, consisting of a DPM integrated onto the gate of a MOSFET. f Dynamics of the neuro-transistor integrate-and-fire process. The left panel shows a sequence of input spikes at high frequency (20 µs intervals, blue line), the potential of the series capacitor (black lines), and the axon membrane current (red line) indicated in e. In the right panel, identical pulses with 80 µs intervals were applied, leading to a much slower firing rate
