Thickness dependence of resistive switching characteristics of the sol-gel processed Y₂O₃ RRAM devices

In this study, yttrium oxide (Y₂O₃)-based resistive random-access memory (RRAM) devices were fabricated using the sol-gel method. The fabricated Y₂O₃ RRAM devices exhibited conventional bipolar RRAM device characteristics and did not require a forming process. The Y₂O₃ film thickness was controlled by varying the liquid-phase precursor concentration. As the concentration increased, thicker Y₂O₃ films were formed. In addition, the concentration of oxygen vacancies increased. The RRAM device properties were not observed for thin Y₂O₃ films, which had the lowest oxygen vacancy concentration. Moreover, RRAM devices, which consisted of the thickest Y₂O₃ films with the largest oxygen vacancy concentration, showed poor non-volatile properties. The optimized Y₂O₃-based RRAM devices with a thickness of 37 nm showed conventional bipolar RRAM device characteristics, which did not require an initial forming process. The fabricated RRAM devices showed a high resistance state to low resistance state ratio of over 10⁴, less than +1.5 V of SET voltage, and −15.0 V of RESET voltage. The RRAM devices also showed promising non-volatile memory properties, without significant degradation after 10³ s retention and 10² cycle endurance tests.