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

Abstract

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°C. By superimposition of RF and DC magnetron sputtering, we were able to fabricate VO2 films with high solar transition efficiency (△Tsol) of 12.8% at a substrate temperature of 300°C, which was comparable to the results attained at 450°C by conventional DC sputtering. The VO2 crystallization at a lower temperature of 300°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°C exhibited a reduced transition temperature of 59°C and a narrow hysteresis width of 3°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.