Change in electronic state of nitrogen in oxidized titanium nitride

Abstract

The changes in the electronic state and local structure of nitrogen in TiN powders heated in air were investigated by X-ray diffraction, diffuse reflectance, X-ray photoelectron spectroscopy (XPS), and X-ray absorption near-edge-structure (XANES) measurements. The oxidation of TiN powder accompanied by desorption of nitrogen started from the surface of the powder particle, resulting in a transformation from TiN to TiO2 with increasing heating temperature. The diffuse reflectance spectra showed the formation of nitrogen-doped TiO2 with an absorption band at 2.9 eV by heating TiN powder above 600 °C. XPS measurement revealed the presence of nitrogen with a negative charge in TiN powders and with a neutral or positive charge in highly-oxidized powders containing a small amount of nitrogen. XANES measurement for nitrogen clarified the presence of nitrogen bound to oxygen which form some complex species such as NO molecule in the powders oxidized above 400 °C.