N-derived signals in the x-ray photoelectron spectra of N-doped anatase TiO2

The plasma-assisted molecular beam epitaxial anatase TiO2-xNx (x < 0.3) films were chosen to investigate the N-derived variation in the x-ray photoelectron spectroscopy (XPS). With increasing nitrogen concentration, the small chemical shift and the shoulder of the main peak emerge in the N 1s, O 1s, or Ti 2p(3/2) core level spectra. In combination with the experimental results obtained from x-ray diffraction and atomic force microscopy, the variations in the spectra could be ascribed to the microstructural distortion. This distortion, induced by the N-3- substitution for lattice O2-, could slightly decrease the average ionicity of the Ti-O (or N) bonds. In addition, the other N 1s features (at 399.8 and 401.8 eV) and the oxygen vacancy are also discussed. For the N-doped TiO2, this work introduces a correlation between the microstructural properties and the XPS signals. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3143882]