Sol-Gel Preparation of HfO ₂ Films and Their Resistive Switching Characteristics under Different Annealing and Test Conditions

In this study, Pt/HfO 2 /Pt sandwich-structured resistive switching (RS) devices are fabricated using the sol-gel method. The effects of annealing oxygen partial pressure (0.001-1 atm), test environments (air, low vacuum, and high vacuum), ambient temperature (250-350 K), and compliance current on the RS performance of HfO 2 films are systematically investigated. It is found that a reduction in annealing oxygen partial pressure significantly increases the oxygen vacancy (Vₒ) concentration, thereby decreasing the Set voltage from 3.3 V (1 atm O 2 ) to 2.1 V (0.001 atm). However, an excessive Vₒ concentration degrades the RS performance. The optimal RS performance is achieved in samples annealed in ambient air, exhibiting a resistance ratio of ~40 and a figure of merit of 13.7. The atmospheric regulation experiments reveal that superior RS performance is achieved under low-vacuum conditions (100 Pa), while high-vacuum environments (10 -4 Pa) significantly impede the Reset operation owing to pronounced oxygen depletion, consequently reducing the switching window. The variable-temperature characteristics demonstrate that reduced ambient temperatures suppress oxygen ion (O 2- ) migration, leading to increased Set voltages, but also enhance the stability of the resistive states. Furthermore, compliance current experiments reveal that thermal accumulation promotes O 2- migration, enabling resistive state transitions below the Reset voltage. This finding suggests a thermally assisted electric-field-driven mechanism, in which Joule heating enhances oxygen vacancy migration, thereby promoting conductive filament rupture. These studies provide new insights into the RS mechanism of inert-electrode/HfO 2 systems and offer valuable guidance for the development of high-performance RS devices.