Low-temperature deposition of thermochromic VO2 thin films on glass substrates

Highly dense and highly crystalline vanadium dioxide (VO2) thermochromic thin films were successfully sputter-deposited on glass substrates at a low substrate temperature of 300 degrees C. By superimposition of RF and DC magnetron sputtering, we were able to fabricate VO2 films with high solar transition efficiency (Delta T-sol) of 12.8% at a substrate temperature of 300 degrees C, which was comparable to the results attained at 450 degrees C by conventional DC sputtering. The VO2 crystallization at a lower temperature of 300 degrees C could be achieved using a high-energy and high-density plasma induced by RF-superimposed DC sputtering. The hysteresis curves of transmittance as a function of temperature revealed that the VO2 films by RF-superimposed DC sputtered at 300 degrees C exhibited a reduced transition temperature of 59 degrees C and a narrow hysteresis width of 3 degrees C. The enhanced transition properties might result from the compressive stress in the b and c axes as well as the densification of the films due to ion bombardment effect. (C) 2016 Published by Elsevier B.V.