Structural defects and electronic structure of N-ion implanted TiO2: Bulk versus thin film

Systematic investigation of atomic structure of N-ion implanted TiO₂ (thin films and bulk ceramics) was performed by XPS measurements (core levels and valence bands) and first-principles density functional theory (DFT) calculations. In bulk samples experiment and theory demonstrate anion N → O substitution. For the thin films case experiments evidence valuable contributions from N₂ and NO molecule-like structures and theoretical modeling reveals a possibility of formation of these species as result of the appearance of interstitial nitrogen defects on the various surfaces of TiO₂. Energetics of formation of oxygen vacancies and its key role for band gap reduction is also discussed.