Vanadium oxide thin films on quartz and Al6061 with reduced phase transition temperature and low solar absorptance for advanced thermal control application in space

Abstract

Doped and co-doped vanadium oxide (VO) thin films were deposited on quartz substrates with varying concentrations of doping elements by sol-gel spin coating technique. The VO thin films were characterized by the X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), cross-sectional FESEM and X-ray photoelectron spectroscopy (XPS) techniques. The optical properties, e.g., the average solar absorptance (αs), the average solar reflectance (ρs) and the average solar transmittance (τs) of the films deposited on quartz were evaluated by using a solar spectrum reflectometer. Based on the optical characterizations, an optimized doping concentration was identified. Further, a process optimized condition was utilized to grow both doped and co-doped vanadium oxide films on metallic Al6061 substrates; which are generally used in spacecraft. The phase transitions of all as grown vanadium oxide films on Al6061 were characterized by the differential scanning calorimetry (DSC) technique. The thin films showed reversible and repeatable phase transitions at sub-zero level of temperatures e.g., ∼ ( ̶ 23.3 °C). Thus, the VO thin films developed in the present work emerge out to be of paramount importance for the smart radiative device applications in spacecraft.