Size and crystallinity control of dispersed VO2 particles for modulation of metal–insulator transition temperature and hysteresis

Abstract

VO₂ particles with a reduced size enable the optimization of its metal–insulator transition (MIT) temperature and hysteresis width. The accurate modulation of particle size and the underlying mechanism of transition behavior remains a critical issue. In this study, the annealing process of a V₂O₅ precursor film was systematically controlled with the guidance of the V–O phase diagram. The film undergoes a synergistic solid-state dewetting and pyrolysis process in the first step to form dispersed VO₂ particles, and then a crystallization process to achieve the preferred orientation, which allows fine control of the particle size and crystallinity by thickness control of the precursor film. Then, the MIT behavior of VO₂ particles with controlled sizes 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 °C without hysteresis was realized. Size dependent crystallinity, strain and defect analyses showed that compressive stress dominates the MIT behavior of larger sized particles, while surface tensile stress and surface defect effects become prominent in smaller sized particles. This work provides a feasible strategy to control the size effect of dispersed VO₂ particle films and deepen our understanding on the MIT behavior in single domains.