X-ray Photoelectron Spectroscopy Analysis of Nitrogen-Doped TiO2 Films Prepared by Reactive-Ion-Beam Sputtering with Various NH3/O2 Gas Mixture Ratios

Nitrogen-doped TiO2 films were prepared by reactive ion-beam sputtering deposition (IBSD) in a mixed atmosphere of NH3 and O-2 at a substrate temperature of 400 degrees C. X-ray photoelectron spectra revealed the presence of six ions, i.e., N3-, N2-, N1-, N+, N2+, and N3+, respectively, in the films. The amorphous films had complex, randomly oriented chemical bonds. The Tauc-Lorentz model was employed to determine the bandgap energy of the amorphous films prepared using different NH3/O-2 gas mixing ratios by ellipsometry. In addition, the optical constants of the films were measured. With the increase in the NH3/O-2 gas mixture ratio to 3.0, the bandgap of N-doped TiO2 narrowed to similar to 2.54 eV.