Analysis of nonpolar resistive switching exhibited by Al/CuxO/Cu memristive devices created via room temperature plasma oxidation

Resistive memory devices based on plasma oxidized copper have been shown previously; however, the influence of the reactive ion etch (RIE) power on device operating parameters has not been established. To investigate this relationship, Cu_xO was produced on blanket ECD copper substrates by room temperature plasma oxidation under varying RIE powers levels. The RIE power was varied from 100-300 W, yielding copper oxide thicknesses ranging from 40-625 nm, as determined by SIMS analysis. This analysis also indicated that Cu:O atomic ratios of the resulting films increased from 1:1-3:2 with increasing RIE power. Following copper oxide formation, 400 nm thick aluminum top contacts (100 um diameter) were patterned with a shadow mask, resulting in Al/Cu_xO/Cu resistive memory devices. Devices from each sample exhibited both stable bipolar and unipolar switching behaviors over repeated set/reset measurements; however, device stability decreased with oxide thickness such that the RIE 100 W sample (~40nm oxide) possessed the best switching characteristics. This nonpolar behavior was operable with set and reset voltages of ± 2-3 V and ± 0.5V, respectively, with an average maximum reset current less than 8 mA (Fig. 1A & IB). R_OFF/R_ON ratios of up to 4,000 were observed.