Analysis of nonpolar resistive switching exhibited by Al/Cu x O/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 x O 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 x O/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 & 1B). R OFF /R ON ratios of up to 4,000 were observed.