NiO films were prepared on Pt/Ti/SiO2/Si substrates by rf reactive sputtering. The voltage-current characteristics of the Pt/NiO/Pt structures showed reproducible resistive switching behaviors at room temperature. The high- and low-resistance states were retained without applying an external bias voltage; the high- to low-resistance ratio was greater than 10. To investigate the influence of the oxygen content on the electrical properties, voltage-current characteristics of NiO films grown at various oxygen contents were investigated. As oxygen content increased from 5% to 10%, the resistance value of the NiO film drastically increased, and a resistive switching behavior was observed. However, as the oxygen content increased to 20%, the resistive switching behavior disappeared. The change in switching behavior was discussed in terms of Ni vacancies and compensating holes inside the NiO film. In addition, the memory properties of NiO-based resistive random-access memory were also investigated. (c) 2006 American Vacuum Society.