Investigation of nitrogen-doped TiO₂ thin films grown by reactive pulsed laser deposition

Nitrogen-doped titanium dioxide (TiO₂) thin films were synthesized on glass substrates by reactive pulsed laser deposition technique (PLD). A frequency quadrupled Nd:YAG (λ = 266 nm, τ_FWHM ≅ 5 ns, ν = 10 Hz) laser source was used for the irradiations of TiO₂ targets. The experiments were performed in controlled reactive atmosphere consisting of mixtures of oxygen and nitrogen gases. We demonstrated that there exists the possibility for the accurate control of the nitrogen incorporation through the growth parameters, i.e., the nitrogen partial pressure in the reaction enclosure. The substitutional nitrogen doping of the anatase phase TiO₂ thin films allows for the continuous shift of the optical absorption edge towards the visible spectral range. When a threshold value of the nitrogen dopant level is surpassed the crystallization structure of the TiO₂ anatase phase thin films changes, and the onset of a stable titanium-oxinitride phase formation takes place.