Resistive Switching in Solution-Processed Copper Oxide (Cu<i>_x</i>O) by Stoichiometry Tuning

Abstract

The control of resistive switching, in low-cost solution-processed CuxO thin films, was demonstrated on the basis of intentional manipulation of intrinsic point defects. Cu interstitials offered a unique way to create metallic Cu filament even in the absence of electrochemically active Cu top electrode. The concentration of these Cu interstitials was controlled by annealing the CuO films at low temperature (300 °C) in Ar environment with different oxygen contents. By varying the oxygen content, profound effect was observed on the resistivity of CuxO thin films, which in turn controlled the memory windows in different devices. Annealing at 0% O2 atmosphere created abundant cationic defects, which resulted in poor switching behavior. With the addition of 20% oxygen and increased annealing time, transition of CuO to Cu2O, determined by X-ray diffraction and Raman spectroscopy, resulted in deterministic increase in on/off ratio by 3 orders of magnitude and improved endurance. On increasing the oxygen content above 20%, switching behavior was degraded. Increasing the oxygen content reduces the cationic defects, which cause hindrance in the formation of filament responsible for switching behavior. Grain boundaries seem to play a vital role in controlling the variation in SET and RESET voltages. We found that precise control on the switching properties can be attained by modulating the Cu interstitials in these CuxO devices.