Effect of oxygen vacancy concentration on the resistive random access memory characteristics of NiO_x (x = 1, 0.97, 0.94) thin films

Polycrystalline NiO thin films with controlled oxygen vacancy concentration were deposited on Pt/Ta/SiO₂/Si substrates using RF sputtering. Auger electron spectroscopy experiments confirmed that the NiO thin films exhibit approximately stoichiometric compositions of NiO, NiO_0.95, and NiO_0.94. These compositions were achieved using sputtering targets with controlled oxygen vacancy concentrations. The NiO resistive random access memory (RRAM) capacitors exhibited reduced formation voltage, SET voltage, and RESET voltage with increasing oxygen vacancy concentration. The decrease in forming, SET, and RESET voltages is attributed to the reduced Schottky barrier caused by oxygen vacancies at the Pt electrodes-NiO thin films interface. In particular, the increase in the oxygen vacancy concentration has the effect of reducing the voltage distributions of the forming, SET, and RESET voltages. Therefore, the results of this study are expected to be utilized in RRAM technology by understanding the values and distributions of formation voltages, SET voltages, and RESET voltages according to changes in oxygen deficiency concentration in the NiO RRAM capacitors.