Tuning the phase transition temperature, electrical and optical properties of VO2 by oxygen nonstoichiometry: insights from first-principles calculations

Abstract

Vanadium dioxide (VO₂) is one of the most promising thermochromic materials with a reversible metal–insulator transition (MIT) from a high-temperature rutile phase to a low-temperature monoclinic phase, although a high MIT temperature (T_c) of 340 K for bulk VO₂ restricts its wide application. Our first-principles calculations show that the oxygen nonstoichiometry plays an important role in tuning the MIT behavior of VO₂. The O-vacancy in bulk VO₂ gives rise to an increase in electron concentration, which induces a decrease in T_c. On the other hand, O-vacancy and O-adsorption on VO₂(R) (1 1 0) and VO₂(M) (0 1 1) surfaces could alter their work functions and in turn regulate T_c. In addition, the formation and adsorption energies of O-adsorption on the two types of surfaces are negative, indicating that VO₂ surfaces are prone to oxidation in ambient air. The present results contribute to both tuning phase transition behaviors experimentally and reducing hindrances for the advanced applications of VO₂-based materials.