Multi-functional TiO2/Si/Ag(Cr)/TiNx coatings for low-emissivity and hydrophilic applications

Abstract

Multi-functional (coatings with some additional functional properties such as high transparency, antireflection, hydrophilicity and antifogging) coatings are indispensable for the modern energy saving systems. In this regard, we deposited TiO2/Si/Ag(Cr)/TiNx multilayer thin films on soda-lime glass by using RF and DC magnetron sputtering to achieve a multi-functional thin film stack with the combination low-emissivity (low-e) and hydrophilicity properties in addition to the high transparency. Primary deposition of Ag(Cr)/TiNx was tried for the low-e effect and successfully obtained a very low emissivity value of 0.067, and then Si and TiO2 films with different bandgap were subsequently deposited to provide the hydrophilic properties. X-ray diffraction results revealed the anatase phase formation of TiO2 after annealing the films at 673K by using the rapid thermal annealing system. Rutherford Backscattering Spectrometry (RBS) was carried out to determine the chemical composition and elemental depth distribution. The multilayer stack exhibited superhydrophilicity with a water contact angle of about 5° after irradiation by UV light. A Heterojunction film with wide and narrow bandgap semiconductor materials was effective to improve the hydrophilicity. The films exhibited a high visible transmittance (∼85.5%, at 550nm) and low infrared transmittance (7%, at 2000nm) including low-e and superhydrophilicity.