  Vanadium dioxide (VO2) as a phase-change material controls the transferred
heat during phase transition process between metal and insulator states. At
temperature above 68C, the rutile structure VO2 keeps the heat out and
increases the IR radiation reflectivity, while at the lower temperature the
monoclinic structure VO2 acts as the transparent material and increase the
transmission radiation. In this paper, we first present the metal-insulator
phase transition (MIT) of the VO2 in high and low temperatures. Then we
simulate the meta-surface VO2 of metamaterial reflector by Ansys HFSS to show
the emittance tunability of the rutile and monoclinic phase of the VO2. In next
section, we will review the recent progress in the deposition of thermochromic
VO2 on glass and silicon substrate with modifying the pressure of sputtering
gases and temperature of the substrate. Finally, we present the results of the
in-situ sputtered VOx thin film on thick SiO2 substrate in different
combination of oxygen and argon environment by V2O5 target at temperature
higher than 300C and then, analyze it with x-ray diffraction (XRD) method. The
thermochromic VO2 based metamaterial structures open a new route to the passive
energy-efficient optical solar reflector in the past few years.
