Resistive switching of HfO2-based Metal–Insulator–Metal diodes: Impact of the top electrode material

This paper deals with the impact of the top metal electrode on the resistive switching properties of HfO2-based Metal-Insulator-Metal diodes. By screening five different metals as top electrode, Al–Cu–Hf–Pt–Ti, we have demonstrated the feasibility of the resistive switching effect on HfO2. Metals with a low enthalpy of formation of oxides ΔHf0 (Pt and Cu) lead to uni-polar switching whereas easily oxidizable metals with a higher ΔHf0 (Al, Hf and Ti) lead to bipolar switching. Cu-, Hf- and Pt-based devices show a degradation of the top electrode after the forming step by the formation of bubbles whereas such phenomenon was not observed in Al- and Ti-based devices. 200 switching cycles were performed on each device in order to extract the main parameters of the resistive switching effect: ION and IOFF currents in the mA range, ROFF/RON resistance ratio up to 5, Vset and Vreset, voltage levels around 1 V, and powers dissipated during read and write operations in the μW and mW range, respectively. For all systems, the reset process dissipates higher power than the set process. From these results, the Ti top adlayer shows the best performance in terms of stability and resistive switching characteristics.