Combined Effect of Temperature Induced Strain and Oxygen Vacancy on Metal‐Insulator Transition of VO₂ Colloidal Particles

Abstract

Vanadium dioxide (VO 2) is a promising material in the development of thermal and electrically sensitive devices due to its first order reversible metal-insulator transition (MIT) at 68 °C. Such high MIT temperature (T C) largely restricts its widespread application which could be enabled if a straightforward tuning mechanism were present. Here this need is addressed through a facile approach that uses the combined effects of temperature induced strain and oxygen vacancies in bulk VO 2 colloidal particles. A simple thermal annealing process under varying vacuum is used to achieve phase transformation of metastable VO 2 (A) into VO 2 (M2), (M2+M3), (M1) and higher valence V 6 O 13 phases. During this process, distinct multiple phase transitions including increased as well as suppressed T C are observed with respect to the annealing temperature and varied amount of oxygen vacancies respectively. The latent heat of phase transition is also significantly improved upon thermal annealing by increasing the crystallinity of the samples. This work not only offers a facile route for selective phase transformation of VO 2 as well as to manipulate the phase transition temperature, but also contributes significantly to the understanding of the role played by oxygen vacancies and temperature induced stress on MIT which is essential for VO 2 based applications.

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“…This result can be further verified by Raman spectrum. The sputtered VO 2 film exhibits strong M 1 phase characteristics, and is accompanied by weak M 2 phase (131.09 cm −1 ) and A phase (966.88 cm −1 ) peaks 45 . The VO 2 film grown by PLD is pure M 1 phase, and it is found that the photo-induced phase transition is caused by the transition from M 1 phase to R phase.…”

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“…10a and b. 141,142 The combined effect of temperature-induced strain and oxygen vacancies is intrinsic to phase evolution. Due to the increased crystallinity, the latent heat of phase transition is also improved.…”