Effect of SiN_x diffusion barrier thickness on the structural properties and photocatalytic activity of TiO₂ films obtained by sol–gel dip coating and reactive magnetron sputtering

We investigate the effect of the thickness of the silicon nitride (SiN_x) diffusion barrier on the structural and photocatalytic efficiency of TiO₂ films obtained with different processes. We show that the structural and photocatalytic efficiency of TiO₂ films produced using soft chemistry (sol–gel) and physical methods (reactive sputtering) are affected differentially by the intercalating SiN_x diffusion barrier. Increasing the thickness of the SiN_x diffusion barrier induced a gradual decrease of the crystallite size of TiO₂ films obtained by the sol–gel process. However, TiO₂ obtained using the reactive sputtering method showed no dependence on the thickness of the SiN_x barrier diffusion. The SiN_x barrier diffusion showed a beneficial effect on the photocatalytic efficiency of TiO₂ films regardless of the synthesis method used. The proposed mechanism leading to the improvement in the photocatalytic efficiency of the TiO₂ films obtained by each process was discussed.