Fig. 4
Nonlinear transmission characteristics and spike-timing-dependent plasticity (STDP) of the memristor device. a Response of a memristor device to different pulse programs; b Emulation of STDP learning rule in Pt/HfOx/ZnOx/TiN memristive device—the relative change of the memristor synaptic weight (ΔW) versus the relative spike timing (Δt). And the solid line is the fitting exponential curve to the experimental data. The insets illustrate various spike schemes. The pulse pair comprises a positive and a negative voltage pulse with amplitude of 1.0 V and width of 50 ms. The interval between the two pulses is Δt ms (t = ±10n, n = 1, 2, …, 10). The current compliance is not set in the whole emulation process. The current values are read at 0.1 V after 5 min of the spikes