Thickness effect on the bipolar switching mechanism for nonvolatile resistive memory devices based on CeO₂ thin films

Impact of switching layer thickness on the bipolar resistive memory performance, stability and uniformity has been investigated in Ti/CeO₂/Pt devices. XRD and FTIR analyses demonstrate polycrystalline nature of CeO₂ films and the formation of a TiO interface layer. The bipolar switching characteristics like HRS and LRS dispersion are found to be dependent on the thickness of CeO₂ layer. As it is noted that forming as well as SET voltages gradually increase with increasing CeO₂ layer thickness however RESET voltages are slightly affected. Oxygen gettering ability of Ti causes the formation of TiO layer, which not only extracts oxygen ions from the ceria film but also acts as ion reservoir, hence plays a key role in stable functioning of the memory devices. Current transport behavior is based upon Ohmic and interface modified space charge limited conduction. Based on unique distribution characteristics of oxygen vacancies in CeO₂ films, a possible mechanism of resistive switching in CeO₂ RRAM devices has been discussed.