Figure 2.  Characterization of the poly (vinyl alcohol) based vertical-type memristor. (a) A photographic image of the vertical-type memristor prepared on a glass substrate. An inset image illustrates the device configuration. (b) Current-voltage characteristics of the device. (c) Memory retention performances of the device. The read voltage (Vread) of 0.2 V was used in the measurements. (d) Dispersions of the writing (left) and erasing (right) voltages of the device during the 50 cycles. (e) Electrical durability of the device. A cycle test based on the voltage sweeps was performed, and each resistance state was checked at the Vread of 0.2 V. (f) A schematics presenting the multilevel conductances in the device, induced by the control of the CF thickness. (g) Demonstration of the multilevel conductance in the device by tuning the compliance current (CC) condition.