Endurance and Cycle-to-cycle Uniformity Improvement in Tri-Layered CeO2/Ti/CeO2 Resistive Switching Devices by Changing Top Electrode Material

Resistance switching characteristics of CeO₂/Ti/CeO₂ tri-layered films sandwiched between Pt bottom electrode and two different top electrodes (Ti and TaN) with different work functions have been investigated. RRAM memory cells composed of TaN/CeO₂/Ti/CeO₂/Pt reveal better resistive switching performance instead of Ti/CeO₂/Ti/CeO₂/Pt memory stacks. As compared to the Ti/CeO₂ interface, much better ability of TaN/CeO₂ interface to store and exchange plays a key role in the RS performance improvement, including lower forming/SET voltages, large memory window (~10²) and no significant data degradation during endurance test of >10⁴ switching cycles. The formation of TaON thinner interfacial layer between TaN TE and CeO₂ film is found to be accountable for improved resistance switching behavior. Partial charge density of states is analyzed using density functional theory. It is found that the conductive filaments formed in CeO₂ based devices is assisted by interstitial Ti dopant. Better stability and reproducibility in cycle-to-cycle (C2C) resistance distribution and V_set/V_reset uniformity were achieved due to the modulation of current conduction mechanism from Ohmic in low field region to Schottky emission in high field region.