Investigation of structure and properties of N-doped TiO2 thin films grown by APCVD

Using TiCl4, O2, and NH3 as gas precursors, N-doped titanium dioxide films with large areas and continuous surfaces were deposited by atmospheric pressure chemical vapor deposition (APCVD). Measurements were performed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet visible (UV–vis) transmission spectra. Using NH3 as the N-doping source, Ti4O7 is induced into the thin films, and anatase–rutile transformation is inhibited. Compared to pure TiO2, N-doped TiO2 films deposited with lower NH3 flows (<90 sccm) give a relatively narrow band gap (from 3.21 to 2.76 eV), and their visible light-induced photocatalysis and hydrophilicity are much enhanced without a decrease in ultraviolet light activity. Preparation of N-doped TiO2 films by APCVD with low cost and high deposition rate (150 nm/min) is compatible with float glass processing, and has a potential industrial application.