Selective near infrared transmittance control of thermochromic VO2 thin films through colloidal lithography

This paper presents the optical characteristics of 2D honeycomb structured vanadium dioxide (VO2) thermochromic thin films with different pattern size prepared by sol-gel method with adopting colloidal lithography. Pattern sizes of films were varied as a diameter of polystyrene spheres and size of obtained films are 550, 900, and 1230 nm, respectively. Crystal structure of prepared films is monoclinic phase of VO2 (M) and there are no impurities or other oxides. The transmittance curve change was observed for all patterned VO2 thin films and it is strongly correlated with pattern sizes and shapes which can make difference in photonic band gap. In addition, it is found that such transmittance curve change are originated from reflection at certain wavelength section which confirmed by reflectance spectra. (C) 2018 Elsevier B.V. All rights reserved.