Resistive random access memory characteristics of NiO, NiO_0.95, and NiO_0.95/NiO/NiO_0.95 thin films

Resistive random access memory (RRAM) technology is receiving a lot of attention as one of the next-generation nonvolatile memory technologies with a simple device structure and fast operation speed. However, one of the problems that must be solved in RRAM technology is that the distribution of RRAM driving voltages of formation, SET, and RESET voltages is large. In this study, we investigated the RRAM driving voltage of formation, SET, and RESET voltages for Pt/NiO/Pt, Pt/NiO_0.95/NiO/NiO_0.95/Pt, and Pt/NiO_0.95/Pt RRAM capacitors affected by an oxygen-deficient NiO_0.95 layer. X-ray diffraction experiments confirmed that the NiO thin films exhibited reduced grain and worsened crystallinity as the oxygen vacancy concentration increased. In particular, increasing the oxygen vacancy concentration of the NiO thin films reduces the magnitude and the distribution of RRAM operating voltages of formation, SET, and RESET voltages. The decrease in RRAM operating voltages is due to the reduced Schottky barrier due to the increased oxygen vacancy concentration and the formation of a readily conducting filament due to the increased internal oxygen bonding. Additionally, it has been suggested that the reduced distribution of RRAM operating voltages is influenced by the formation volume of the conducting filament formed by increasing oxygen vacancy concentration.