Enhanced Visible Transmittance of Thermochromic VO(2) Thin Films by SiO(2) Passivation Layer and Their Optical Characterization

This paper presents the preparation of high-quality vanadium dioxide (VO(2)) thermochromic thin films with enhanced visible transmittance (T(vis)) via radio frequency (RF) sputtering and plasma enhanced chemical vapor deposition (PECVD). VO(2) thin films with high T(vis) and excellent optical switching efficiency (E(os)) were successfully prepared by employing SiO(2) as a passivation layer. After SiO(2) deposition, the roughness of the films was decreased 2-fold and a denser structure was formed. These morphological changes corresponded to the results of optical characterization including the haze, reflectance and absorption spectra. In spite of SiO(2) coating, the phase transition temperature (T(c)) of the prepared films was not affected. Compared with pristine VO(2), the total layer thickness after SiO(2) coating was 160 nm, which is an increase of 80 nm. Despite the thickness change, the VO(2) thin films showed a higher T(vis) value (λ 650 nm, 58%) compared with the pristine samples (λ 650 nm, 43%). This enhancement of T(vis) while maintaining high E(os) is meaningful for VO(2)-based smart window applications.