Improved optical response for N-doped anatase TiO2 films prepared by pulsed laser deposition in N2/NH3/O2 mixture

Nanostructured N-doped TiO2 films in anatase phase were prepared by laser ablation of titanium target in N2/O2 and NH3/N2/O2, respectively. The films were deposited on glass substrates which were heated to 400 °C. The as-deposited films were characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and atomic force microscope (AFM). Nitrogen doping is more efficient when adding a little NH3 into N2/O2 mixture. The nitrogen concentrations are 2.0% and 4.4% for the films deposited in N2/O2 and NH3/N2/O2, respectively. A remarkable improvement of optical absorption in the visible light region has been detected for the film deposited in NH3/N2/O2. The mechanism for the redshift in photoabsorption spectra of N-doped TiO2 films has been discussed.