Transparent Dielectric TiO2/SiO2 Coatings for Thermal Shielding and Self-Cleaning Applications

The economical fabrication of one-dimensional dielectric reflectors using the hybrid sol-gel spin coating process is significant compared to sophisticated chemical and physical vapor deposition techniques. In this work, we opted for alternate layers of TiO2 and SiO2 films to fabricate near-infrared dielectric reflectors owing to their high refractive index contrast and easy tunability of the reflection window in the desired spectral range. X-ray diffraction (XRD) studies of the monolayer TiO2 and SiO2 confirmed the existence of anatase-TiO2 and amorphous-SiO2 phases, respectively. Spectroscopic ellipsometry investigation of TiO2 and SiO2 films revealed the refractive indices of 2.6 and 1.5, respectively. The field-emission scanning electron microscopy (FESEM) analyses evidenced the fabrication of 2.5 stacks/bilayers of TiO2/SiO2 (TiO2/SiO2)2.5S. The reflectance measurement demonstrated 100% reflection in the near-infrared region with its center wavelength of 833 nm. In addition, we have examined the water contact angle of various samples using the sessile drop technique, and 2.5 stacks-based reflector showed its lowest contact angle of 29.3o, which suggests its anti-fogging and self-cleaning applications.