Tuning Effect of N₂ on Atmospheric-Pressure Cold Plasma CVD of TiO₂ Photocatalytic Films

To deposit TiO2 films through plasma CVD, the partial pressure ratio of O₂ to TiCl₄ should be greater than the stoichiometric ratio (pO2=pTiCl₄ > 1). However, this may lead to the formation of powder instead of film on the substrate when using volume dielectric barrier discharge (volume-DBD) at atmospheric pressure. In this study, by adding N2 into the working gas Ar, TiO₂ photocatalytic films were successfully fabricated in the presence of excess O₂ (pO₂=pTiCl₄ = 2:6) by using a wire-to-plate atmospheric-pressure volume-DBD. The tuning e®ect of N₂ on the deposition of TiO2 film was studied in detail. The results showed that by increasing the N₂ content, the deposition rate and particle size of the TiO₂ film were reduced, and its photocatalytic activity was enhanced. The tuning mechanism of N₂ is further discussed.