Durability of thermochromic VO2 thin films under heating and humidity: Effect of Al oxide top coatings

Abstract An explorative study was performed on sputter-deposited thermochromic (TC) VO 2 films exposed to heat treatment under dry and humid conditions. The ambient conditions were harsh and 80-nm-thick VO 2 films were rapidly converted to non-TC V 2 O 5 . It was found that a 30-nm-thick sputter-deposited Al oxide top coating provided good protection and delayed the oxidation for more than one day upon heating in dry air at 300 °C and that protection occurred for several days at 95% relative humidity and 60 °C. The thickness of the Al oxide was important and, expectedly, increased thickness yielded enhanced protection. Our results are important for TC fenestration as well as for other technical applications.