Fig. 2: Structure and electrical characterization of the flexible VO₂ memristor.

a Photograph of flexible VO₂ memristors developed in this work (top right: enlarged scanning electron microscope (SEM) image of the planar structure, bottom right: magnified SEM image of the channel with a length of 500 nm). b Typical threshold switching (TS) characteristic of the VO₂ memristor. The current-voltage (I-V) sweeps show no variation after the 2000 cycles. c The endurance test showing no degradation of signals over 10¹² cycles by applying the pulse pair of 3.0 V/1 μs and 0.5 V/1 μs. In-situ scattering-type scanning near-field optical microscopy (s-SNOM) image of the device ON/OFF area under 1 switch (d) and 10¹⁰ switches (e). The morphology of the conductive channel did not show observable changes after 10¹⁰ switches. f The TS characteristics of the flexible VO₂ memristor under different bending radii (r from 10 to 1 mm). g Comparison of reported silicon-based^{21,22,42,43,44,45,46} and flexible^{37,38,39,40,41} neuronal switching devices with the present VO₂ memristor in terms of endurance and flexibility characteristics. The device-to-device variation of the threshold voltage (V_th) (h) and holding voltage (V_hold) (i) from 15 × 15 memristor matrix showing a 97.8% device yield.