Enhancing the nonvolatile properties of sol-gel-processed Y₂O₃ RRAM devices by suppressing oxygen vacancy formation

In this study, Y₂O₃-based resistive random-access memory (RRAM) devices with an Ag/Y₂O₃/indium tin oxide structure are fabricated on a glass substrate via sol-gel processing. These Y₂O₃ RRAM devices demonstrate typical bipolar resistance-switching characteristics without requiring a high-voltage forming process. The presence of oxygen vacancies in the metal-oxide layers alters the electrical properties of these devices. To control the oxygen vacancy concentration, the post-annealing temperatures are varied between 300 and 500 °C. As this temperature increases, the concentration of formed oxygen vacancies decreases. The RRAM devices annealed at 500 °C feature a reduced number of oxygen vacancies in Y₂O₃, initially exhibiting the highest high-resistance state. This yields the highest high-to low-resistance state ratio exceeding 10⁵. Moreover, the Y₂O₃ RRAM devices annealed at 500 °C exhibit the highest number of endurance cycles (∼10³) and good data-retention times (∼10⁴ s). In addition, the reduced oxygen vacancy concentration in these annealed Y₂O₃ films suppresses the excessive formation of conductive filaments in the low-resistance state and decreases the leakage current in the high-resistance state. Overall, these changes yield a high-to low-resistance state ratio and improved endurance characteristics owing to the reduced oxygen vacancy concentration in the Y₂O₃ films annealed at 500 °C.