Nitrogen Location and Ti–O Bond Distances in Pristine and N-Doped TiO2 Anatase Thin Films by X-ray Absorption Studies

Abstract

This Article reports detailed extended X-ray absorption fine structure (EXAFS) analysis of spray pyrolysis synthesized TiO2 thin films to locate the position of nitrogen in N-doped phase pure (anatase) TiO2 and evaluate Ti–O bond distances and the coordination number of Ti. The thin films were synthesized at three different substrate temperatures viz. 400, 450, and 500 °C leading to concomitant occurrence of varying nitrogen concentration (N/Ti) of 0.282, 0.237, and 0.24, respectively. The coordination number extracted from the EXAFS fitting revealed that films synthesized at 450 °C are stoichiometric, whereas those synthesized at 400 and 500 °C are substoichiometric. The intensity of near edge peaks in XAS was employed to delineate the contribution from both symmetry of TiO6 polyhedra and particle size. The axial and equatorial Ti–O bond distances, corresponding to the different nitrogen concentrations, extracted from the EXAFS fitting, showed good agreement with those calculated from density functional ...