Role of the top electrodes and their interfaces on the resistive switching behavior of epitaxial NiO thin films

Initial I-V characteristics of resistive switching behavior have been investigated with epitaxial NiO films grown on (100) SrRuO$_3$ by using Al, Pt, and CaRuO$_3$ as the top electrodes. SRO/NiO/Al and SRO/NiO/Pt require an electroforming process for the initialization of the resistive switching, while SrRuO$_3 $/NiO/CaRuO$_3$ is initially in a low-resistance state. The temperature dependence of the initial I-V characteristics indicates that insulating layers exist at the NiO/Al and NiO/Pt interface, presumably broken by the electroforming process. On the other hand, SRO/NiO/Al does not show the resistive memory switching behavior despite the electroforming behavior. The resistive switching endurance is also distinct depending on the top electrodes. Our results suggest that the oxygen defects and their bonding energy with the top electrode metal play a critical role on the resistive switching behavior.