Nitrogen-doped titanium dioxide—Characterization of structural and optical properties

We have chosen oxidation of titanium nitride, TiN, in air atmosphere as a preparation method of nitrogen-doped titanium dioxide for photocatalytic application. Powders and thin films were selected for systematic studies. Self-propagating high-temperature synthesis (SHS) and dc reactive magnetron sputtering were used for elaboration of stoichiometric TiN powder and thin films, respectively. Samples microstructure was studied by means of AFM and SEM. The phase and chemical composition were investigated by means of XRD and XPS. The optical spectra were measured over the visible and UV ranges of light spectrum. SEM images of powders revealed a change in grain shape from sharp-edged TiN grains with well-defined facets to regular and oval TiO2. XRD studies set out the temperature limit of TiN existence at 400 °C. XPS investigations confirmed nitrogen presence in TiO2 lattice even at 500 °C. Optical analysis revealed an additional absorption over the visible range – powders, and a shift of the fundamental absorption edge towards visible range of the light spectrum – thin films.