Improvement of resistance switching characteristics in NiO films obtained from controlled Ni oxidation

Bi-stable resistive switching phenomena controlled by external voltages has drawn much attention for high-density nonvolatile memory devices, the resistive memory materials ranging from organic to inorganic materials, with either metallic or conductive oxide electrodes. These resistive switching phenomena have been reported in many simple transition metal oxide films such as CuO_x, TiO₂, NiO or ZrO₂. The switching mechanism in Metal/Resistive oxide/Metal (MRM) structures has been attributed to the reversible formation/rupture of filamentary conducting paths at the interfaces between metal electrodes and bi-stable oxide film. Recently, we have explored the possibility to form memory cells from the partial oxidation of blanket Ni metallic bottom electrode. The switching characteristics were progressively improved by optimizing annealing conditions and selecting appropriate substrates on which nickel film was sputtered. Reversible and repetitive resistive switching phenomena with set/reset voltages around plusmn1 V were demonstrated in NiO/NiO/Ni structures fabricated from Ni/TiN/Ti/SiO₂/Si₂N₄/Si substrates.