Thermally oxidized nickel oxide films for development of high performance nonvolatile bipolar resistive random-access memories

Abstract

This study employs a thermal oxidation process to transform a Ni metal film into a NiO_x layer and fabricate a high-performance Ag/NiO_x/n⁺-Si resistive random-access memory (RRAM). Initially, small grains are observed in the SEM image of the Ni film. After the oxidation process, the Ni film converts into a NiO_x layer with larger grains. XRD analysis indicates that the NiO_x film is mainly composed of NiO bunsenite phase with a grain size of 39.8 nm, and no detectable diffraction peaks corresponding to Ni₂O₃ or other phases are observed. Furthermore, XPS depth profile analysis verifies that the entire Ni film has been transformed into a NiO_x layer. The Ag/NiO_x/n⁺-Si device exhibits stable bipolar resistive switching (RS) behavior, achieving a large memory window of 10⁶ and stable endurance over 10³ DC switching cycles. Data retention and read-disturb immunity tests confirm that the device can reliably maintain the resistance states for over 10⁴ s. These results demonstrate the suitability of Ag/NiO_x/n⁺-Si RRAM for future high-performance and cost-effective memory technologies.