Abstract

The thermochromic properties of vanadium dioxide have been deeply investigated since 1959 when Morin reported for the first time the evidence of the semiconductor-metallic phase transition (SMT) [1]. The attention given to the material is due to its extraordinary feature of drastically changing the electrical properties (electrical conductivity may change up to 5 orders of magnitude) as well as the optical properties during the SMT (first-order phase transition) from the semiconductor state (rutile crystallographic structure), to the metallic state (monoclinic structure), taking place at a critical temperature of about T_c 68°C with a very narrow hysteresis if single crystal. In synthesis at high temperatures (T>T_c) vanadium dioxide exhibits metallic properties, showing a high electrical conductivity, and inhibiting the propagation of electromagnetic waves. On the contrary at low temperatures (T<T_c) VO₂ behaves as a semiconductor, showing a relatively high transparency in the infrared spectral range. Thanks to the SMT, that is ultrafast, vanadium dioxide is a unique material, very promising for various applications (“smart” windows, thermally controllable localized-plasmon, ultrafast switching of the photonic stop band in photonic crystals, and manipulation of the infrared emission [2,3]).

© 2015 IEEE