Effect of oxygen-deficient NiO _1−δ layer thickness on the resistive random access memory characteristics of NiO thin films

The resistive switching characteristics of NiO resistive random access memory (RRAM) capacitors composed of NiO thin films are influenced by variations in the oxygen concentration inside the NiO thin films. In this study, we investigated the RRAM characteristics of capacitors fabricated with a NiO thin film and an oxygen-deficient NiO 0.95 layer adjacent to each of the two electrodes. Polycrystalline NiO thin films and oxygen-deficient NiO 0.95 thin films were deposited on Pt/Ta/SiO 2 /Si substrates by radiofrequency sputtering. The thicknesses of the NiO thin films were 50 nm and those of the NiO 0.95 layers were 5 and 10 nm. It was confirmed that the NiO 0.95 layer formed at the boundary with the Pt electrodes plays a role in reducing the forming, SET and RESET voltages by reducing the height of the Schottky barrier. Although the enhancement of RRAM characteristics became more pronounced with increasing thickness of the oxygen-deficient layer, the difference between the devices with 5 and 10 nm layers was small, suggesting a tendency towards saturation.