Size and crystallinity control of dispersed VO2 particles for modulation of metal-insulator transition temperature and hysteresis
VO2 particles with reduced size enable optimization of its metal-insulator transition (MIT) temperature and hysteresis width. Accurate modulation of particle size and the underling mechanism on transition behavior remains a critical issue. In this study, the annealing process of V2O5 precursor film was systematically controlled under the guidance of V-O phase diagram. The film undergoes a solid-state dewetting and pyrolysis synergistic process in the first step to form dispersed VO2 particles, and then a crystallization process to achieve preferred orientation, which allows fine control of the particle size and crystallinity by thickness control of precursor film. Then the MIT behavior on VO2 particle with controlled size from 220 nm to 1.64 μm was systematically investigated. With decreasing size, the MIT temperature decreases and then increases with enlarged hysteresis. A minimum MIT temperature of 41 ℃ without hysteresis was realized. Size dependent crystallinity, strain and defects analysis showed that compressive stress dominates the MIT behavior in larger size, while surface tensile stress and surface defect effect becomes prominent in smaller size. This work provides a feasible strategy to control the size effect of dispersed VO2 particles film and deepen our understanding on the MIT behavior in single domain.