Low temperature rf-sputtered thermochromic VO2 films on flexible glass substrates

The high deposition temperature of the order of 400 o C and more is requirement for the growth of the thermochromic phase of vanadium dioxide (VO2), limits the type of substrates that one may grow them on only to rigid ones. In this work, thermochromic VO2 films were successfully deposited on flexible Corning® Willow® glass substrates, without the use of a buffer layer, by rf sputtering at a substrate temperature of 300 o C, one of the lowest for this technique ever reported. The critical transition temperature of 80 nm thin films was Tc = 50.7 o C, transmittance hysteresis width was ΔT = 12.1 o C, while the modulation of the transmittance at λ = 2000 nm measured at 25 o C and 90 o C was around 36%, leading to a solar modulation of ΔTrsol = 5%. In addition, an increase in transmittance at λ = 600nm (visible region) of 4% was observed before and after heating, while integrated luminous transmittance remained almost constant at Trlum = 34%. The thermochromic and luminous characteristics