The effect of buffer layer on the thermochromic properties of undoped radio frequency sputtered VO2 thin films

Thermochromic (TC) coatings can find use in a wide range of applications. Vanadium dioxide (VO2) specifically, can be potentially used as a smart window coating, as it presents a metal-to-semiconductor transition close to the room temperature (Tc=68°C). This results in low transmission in the infrared (thermal) part of the spectrum, while preserving its transmittance in the visible. In the present work, vanadium dioxide (VO2) thin films with a thickness of ~85nm were prepared by radio frequency sputtering, to investigate the influence of the buffer layer and deposition properties employed, on their thermochromic behavior. The substrates used were uncoated glass and pre-coated glasses with SnO2 or ZnON as buffer layer. The lowest growth temperature applied was 300°C, yielding TC-VO2, without the necessity of any post-growth treatment. The structure of the VO2 films was studied by X-ray diffraction and temperature-dependent micro Raman techniques, and the transition temperatures were determined through transmittance measurements. •RF-sputtered thermochromic VO2, was grown at 300°C and 400°C.•Buffer layers of SnO2 or ZnON are used over glass.•Low Tc, without post-treatment, for both buffer-layers and T-growth•Thermochromicity of glass/VO2, at low T-growth, is improved by ZnON buffer layer.