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

• Vanadium dioxide (VO2) films are formed on glass at 300 °C by RF + DC sputtering.
• The VO2 films deposited at 300 °C show good thermochromic properties (△Tsol ~ 13%).
• 300 °C-deposited VO2 shows a lowered Tc of 59 °C and a narrow hysteresis width of 3 °C.
• Tc and hysteresis width are affected by compressive stress and film densification.

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.