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Vanadium dioxide (VO2) thin films were deposited at room temperature on Corning 2947 glass substrates by direct current (DC) magnetron sputtering with a high purity VO2 target. Crystal structure, surface topography, surface morphology and optical properties of the deposited VO2 thin films were investigated. The deposited films exhibited a single orientation of (110) with a crystallite size of 41.3 nm as confirmed by the X-ray diffraction analysis and Scherrer formula, respectively. From the surface topography analysis, the film surface had root mean square surface roughness of ~6.8 nm and consisted of round-shaped grains. Similarly, from the surface morphology analysis, spherical-like grains were observed on the surface of the deposited VO2 thin films with estimated average grain size of 34.2 nm. The deposited thin films showed high transmittance and low reflectance in the visible and near-infrared wavelength regions at room temperature. In addition, from the optical transmittance against temperature measurements, only a few transmittance variation and a slight change in hysteresis loop were detected during heating and cooling between room temperature and 100 °C. Hence, the deposited VO2 thin films were found to exhibit lack of phase transition.

Investigation on properties of vanadium dioxide (VO2) thin films has received significant attention as it is a thermochromic material potentially for applications on architectural glazing in order to reduce energy consumption from usage of air-conditioning system. Most studies have focused on the hysteresis behavior of thermochromic VO2 thin films that occurs at a certain phase transition temperature. Although large area coating techniques have recently been developed, there are still many obstacles in trying to deploy energy-efficient windows. Hence, this work concisely reviews on VO2 thin films as thermochromic materials, and developments on preparation methodologies in order to enhance the thermochromic characteristics of VO2 thin films.

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