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Issue 44, 2009
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Nitrogen diffusion in doped TiO2 (110) single crystals: a combined XPS and SIMS study

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Abstract

Rutile TiO2 (110) single crystals were doped with nitrogen by heating at 675 °C in flowing NH3 gas. This caused a red shift in the band edge and an increase in visible region absorption. Nitrogen depth profiles obtained using dynamic secondary ion mass spectrometry (SIMS) could best be fitted by assigning three distinct diffusion coefficients. X-Ray photoelectron spectroscopy (XPS) indicated the presence of two surface nitrogen states with binding energies of 395.6 eV (substitutional N) and 399.8 eV (interstitial N). Angle resolved XPS measurements allowed us to link the XPS environments to the SIMS diffusion profiles. Subsequent air annealing at 500 °C led to asymmetric diffusion of the interstitial nitrogen into the bulk, removal of substitutional nitrogen into the gas phase, a decrease in the concentration of Ti3+ and a blue shift in the band edge. These changes could be related to variation in the optical band gap, and it was found that the principle cause of band gap narrowing was substitutional rather than interstitial nitrogen.

Graphical abstract: Nitrogen diffusion in doped TiO2 (110) single crystals: a combined XPS and SIMS study

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Publication details

The article was received on 06 Jul 2009, accepted on 24 Aug 2009 and first published on 01 Oct 2009


Article type: Paper
DOI: 10.1039/B913267H
Citation: J. Mater. Chem., 2009,19, 8418-8425
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    Nitrogen diffusion in doped TiO2 (110) single crystals: a combined XPS and SIMS study

    R. G. Palgrave, D. J. Payne and R. G. Egdell, J. Mater. Chem., 2009, 19, 8418
    DOI: 10.1039/B913267H

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