Secondary ion mass spectrometry and X-ray photoelectron spectroscopy studies on TiO2 and nitrogen doped TiO2 thin films

Anatase phase TiO2 and nitrogen (N) doped TiO2 thin films were synthesized by an ultrasonic spray pyrolysis technique on c-Si (100) substrates in the temperature range 300–550 °C. The former used a precursor solution of titanium oxy acetylacetonate in methanol whereas the later used a titanium oxy acetylacetonate hexamine mixture in methanol. Homogeneity across the film’s thickness and the nature of the film–substrate interface were studied by dynamic depth profiling acquired using secondary ion mass spectrometry SIMS. The stoichiometry and bonding state of various species present in the films were studied using X-ray photoelectron spectroscopy (XPS). N-doping was confirmed by both SIMS and XPS. XPS studies revealed that the nitrogen content of the films synthesized at 300 °C (3.2%) is high compared to that of films made at 350 °C (1.3%).

Research highlights
► N-doped TiO2 thin films were synthesized, in a single step, by spray pyrolysis for the first time.
► The film homogeneity and O/Ti ratio across the film’s thickness is measured using SIMS.
► XPS and SIMS studies shows nitrogen incorporation in to the TiO2 crystal lattice.
► The amount of nitrogen incorporated in the crystal lattice as Ti–N bond is estimated from XPS studies.
► Results obtained from SIMS as well as XPS are corroborated.