Resistive switching mechanism of Ag/ZrO2:Cu/Pt memory cell

Resistive switching mechanism of zirconium oxide-based resistive random access memory (RRAM) devices composed of Cu-doped ZrO₂ film sandwiched between an oxidizable electrode and an inert electrode was investigated. The Ag/ZrO₂:Cu/Pt RRAM devices with crosspoint structure fabricated by e-beam evaporation and e-beam lithography show reproducible bipolar resistive switching. The linear I?CV relationship of low resistance state (LRS) and the dependence of LRS resistance (R _ON) and reset current (I _reset) on the set current compliance (I _comp) indicate that the observed resistive switching characteristics of the Ag/ZrO₂:Cu/Pt device should be ascribed to the formation and annihilation of localized conductive filaments (CFs). The physical origin of CF was further analyzed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). CFs were directly observed by cross-sectional TEM. According to EDS and elemental mapping analysis, the main chemical composition of CF is determined by Ag atoms, coming from the Ag top electrode. On the basis of these experiments, we propose that the set and reset process of the device stem from the electrochemical reactions in the zirconium oxide under different external electrical stimuli.