Fig. 2: Junction structure, electrical characteristics, and synaptic functions of the TaO_y/NP TaO_x memristor synapse.

a Schematic of a memristor synapse with a junction diameter of 200 μm. b Cross-sectional TEM image of the memristor synapse. c Self-rectifying I–V switching curves of the memristor synapse versus the magnitude of V_s (from 4 to 8 V). The inset shows the I–V curves on a linear scale. d Consecutive I–V switching curves (1000 times) at |V_s| = 4 V. e, f XPS depth-profiling analysis of the Ta 4f spectra as a function of the sweeping direction of programing voltage applied to the Pt electrode [V > 0 for (e) and V < 0 for (f)]. V > 0 indicates a voltage sweep from 0 to 10 V and V < 0 indicates voltage sweeping from 0 to −10 V. g Plot of x (or y) in TaO_{x (or y)} as a function of junction depth, showing the change in the \(V_o^{..}\) distribution and position of the Ohmic-like contact at NP TaO_x/Ta. h Plots of PSC as functions of the pulse width (from 20 to 40 ms) in response to potentiating and depressing input-signal trains (100 pulses for each pulse train). Implementation of LTP and LTD. The PSC was read at V_r = 5 V whenever one programming pulse was applied