The Ru-doped VO2 films fabricated by rapid thermal annealing of V–Ru co-sputtered alloy films with lowered phase transition temperature and narrowed hysteresis for smart windows.

Vanadium dioxide (VO2), a current favorite in the field of smart windows as a thermochromic material, faces limitations in practical application due to its high phase transition temperature (Tt, ~ 68 ℃) and wide hysteresis curve (ΔT). In this study, Ru-doped VO2 thin films with reduced Tt and narrower ΔT were prepared through co-sputtering tetravalent metal Ru and V using magnetron sputtering to form alloy thin films, followed by rapid thermal annealing. Compared with pure VO2 thin films, at the Ru doping concentration of 4.98 at%, the Tt was lowered from 59.6 °C to 35.8 °C, and the ΔT was reduced from 10.5 °C to 2.8 °C, primarily due to the structural similarity between RuO2 and rutile phase VO2, smaller grain size, and greater grain uniformity. The optical properties of Ru-doped VO2 thin films had also been discussed, revealing only minor reductions in luminous transmittance (Tlum) and the solar modulation ability (ΔTsol) when the Tt decreased to 35.8 °C. This methodology offers a viable path for applying VO2 in smart windows, providing effective reductions in Tt and ΔT with minimal impact on optical performance. [ABSTRACT FROM AUTHOR]