Thermal annealing effect on nitrogen-doped TiO2 thin films grown by high power impulse magnetron sputtering plasma power source

The work reports plasma assisted growth of nitrogen-doped titanium dioxide (N-TiO2) thin films using high power impulse magnetron sputtering (HiPIMS) power source and effect of post-deposition thermal annealing. The films were deposited at low pressure. The binding energies of elements of interest, the energy gap, crystallinity and morphology of the films were analyzed before and after annealing. The results showed an increase in binding energies, a fact attributed to enhanced oxidation, after the annealing process. Only nitrogen doped samples grown by HiPIMS exhibited the presence of substitutional nitrogen. The energy gap of the films was found to decrease after doping and annealing. Improvement in crystallinity with a small shift in the crystalline peaks indicating decrease in lattice parameter, which could be seen by surface smoothing, was observed after thermal annealing. As a result of the growth of films by HiPIMS, nitrogen doping and post-deposition thermal annealing, improvements in the properties of the films which have relevance for photocatalytic and energy applications were observed.