Thermal evidences for multi-domain coexistence of freestanding VO2 crystalline microbeams with insulator–insulator transitions

Abstract

Vanadium dioxide (VO2) exhibits multiple insulating states and complex transitions, both among these states and to a metallic rutile (R) phase. In this study, we investigate freestanding VO2 microbeams that undergo reversible transitions from an insulating triclinic (T) phase to an insulating monoclinic (M2) phase, followed by a transition to the R phase. The latent heat changes associated with these first-order phase transitions are monitored using a recently developed chip-based differential scanning calorimetry technique, which demonstrates exceptional sensitivity and resolving power. A series of sharp endothermic and exothermic peaks are observed during the temperature ramping process. In contrast to the abrupt and complete transformation typically observed in conventional insulator-to-metal transitions, our findings reveal a scenario in which multiple domains coexist, and phase transitions occur sequentially within each domain. These results underscore the intricate relationship between domain dynamics and the multiple phase structures in VO2. Furthermore, they highlight the potential of advanced thermal analysis techniques to detect subtle thermal signals associated with phase transition processes, providing fresh insights into the underlying mechanisms.