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 N-2 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. (C) 2015 Elsevier B.V. All rights reserved.The XPS measurements and DFT calculations were supported by a grant of the Russian Science Foundation (Project No. 14-22-00004). The sample preparation and ion implantation were supported by Russian Federation Ministry of Science and Education (Government Task 3.2016.2014/K)