Surface wettability and photocatalytic activities of ZrO_xN_y monolayer, ZrO_xN_y/Au bilayer and ZrO_xN_y/Au/TeO₂ trilayer for self-cleaning and antifogging coatings applications

ZrO_xN_y monolayer, ZrO_xN_y/Au bilayer, ZrO_xN_y/Au/TeO₂ trilayer films were investigated for their hydrophilic properties and photocatalytic activities. ZrO_xN_y and Au layers were prepared by dc reactive magnetron sputtering whereas TeO₂ layer was prepared by vapor transport technique. X-ray diffraction revealed the formation of monoclinic ZrO₂ phase for ZrO_xN_y films with low nitrogen content whereas mixed monoclinic and tetragonal ZrO₂ phases were formed for ZrO_xN_y films with higher nitrogen content. The chemical composition of ZrO_xN_y bottom layer affected the growth of the Au layer. The tetragonal TeO₂, in ZrO_xN_y/Au/TeO₂ trilayer, blocked most of ZrO₂ and Au crystallographic peaks. The ZrO_xN_y/Au films are composed of tiny nanoparticles in the range 27–33 nm and the ZrO_xN_y/Au/TeO₂ films have branched-nanowires morphology. ZrO_xN_y monolayer films are hydrophilic and the hydrophilicity decreases then increases with increasing the nitrogen content in the film. Adding an Au layer, then TeO₂ layer over ZrO_xN_y resulted in a pronounced decrease in water contact angle. After UV-illumination the contact angle of the films became almost zero and the surfaces transformed to super-hydrophilic. Nitrogen doping enhances the degradation rate of ZrO_xN_y monolayer film. The highest degradation rate was observed for ZrO_1.9N_0.3/Au/TeO₂ trilayer film. The prepared ZrO_xN_y/Au/TeO₂ trilayer films are good candidates for self-cleaning and antifogging applications.