W/Mg co-doped VO2 thin films with improved transition temperature, optical, and structural properties

W/Mg co-doped VO₂ thin films were prepared by co-sputtering of magnesium, tungsten, and vanadium (V(99%)W(1%) alloy targets at a substrate temperature of 425 °C. The films were characterized by X-ray diffraction, atomic force microscopy, Rutherford backscattering spectroscopy, the two-point probe, and UV/VIS/NIR Spectrometer. W/Mg co-doped VO₂ films with concentrations of~0.95 at.% and~3.1 at.% for W and Mg, respectively, showed relatively lower crystallite sizes and reduced hysteresis loop widths of 3.9 nm and~2 °C compared to 11.4 nm and 17.8 °C, respectively, for pristine VO₂. The integrated luminous transmittance of the co-doped samples was~47%, compared to 26% and 41% for the W-doped and pristine VO₂ films, respectively. A significant reduction in transition temperature to below 33 °C was realized for the co-doped films, compared to 64.8 °C and 44 °C for the undoped and W-doped VO₂-based thin films, respectively. This work shows that a controlled amount of Mg in the W-doped VO₂ films could potentially make VO₂ thin films useful for smart window applications.