Non-volatile and volatile switching behaviors determined by first reset in Ag/TaO_x/TiN device for neuromorphic system

We fabricate the Ag/TaO_x/TiN device and confirm the structure of the element with transmission electron microscopy (TEM) and energy dispersive spectroscopy line scan (EDS). The device shows non-volatile bipolar resistive switching as well as volatile threshold switching. In order to identify the threshold switching, the first reset voltage is needed to activate the device and check how much the current level decreases by the reset voltage. The current gradually increases and drops at a relatively high compliance current (CC) with positive and negative values, respectively. To demonstrate the temporal learning in the volatile switching with short-term memory effect, the states of [1111], [1001], and [1000] 4-bits are controlled by applying different pulse streams, which outputs the letter “P” in the reservoir computing system. At the lowest CC, the abrupt threshold switching is obtained, and the relaxation time in transient measurement is investigated depending on the voltage amplitude.