Microstructure and resistance switching in NiO binary oxide films obtained from Ni oxidation

Oxide Resistive Random Access Memories (OxRRAM) are discussed for future high density non volatile memory chips. NiO and other simple binary transition metal oxides (such as TiO₂, HfO₂ or ZrO₂) have recently attracted much attention. In most cases, polycrystalline oxide films are deposited by reactive sputtering on conductive substrates to form bi-stable Metal/Resistive oxide/Metal (MRM) structures. In this paper, an alternative way is explored to obtain NiO films from the controlled oxidation of a Ni metallic film. Different thermal treatments were evaluated to oxidize the metallic film with conditions preventing the complete consumption of Ni film used as bottom electrode. Process parameters of Rapid Thermal Annealing (RTA) route were adjusted to achieve controlled oxidation. Microstructural and electrical analyzes were performed to apprehend the influence of the process parameters on the switching behavior. Reproducible resistive switching phenomena have been demonstrated in Pt/NiO/Ni structures with threshold voltage varying from 2 to 5 V depending on oxidizing conditions.