Structures and photocatalytic behavior of tantalum-oxynitride thin films

Tantalum oxynitride films were created by direct nitridation/oxidation during rapid thermal annealing at temperatures 450–700 °C. Instead of during deposition, this post process may be proved to be an alternative way to make transition metallic oxynitride films. With sufficient supply of oxygen flow (≥ 30 sccm), TaOxNy was formed as examined from X-ray diffraction (XRD) analysis. This oxynitride film has a broad optical absorption over the range of visible light and sufficient photocatalytic function. For optical absorption, the films' transmittance and reflectance were measured by a UV–VIS–NIR spectrophotometer with wavelengths ranging from 300 to 900 nm. The broad visible light absorption is associated with the formation of band gap in TaOxNy film, which was examined by the theoretical calculations combining the Beer–Lambert law and Tauc formula. Lastly, the photocatalysis of TaOxNy was gauged by the photodegradation test which measured the reduction of light absorbance affected by the decomposition of methylene blue (C16H18N3SCl.3H2O) on TaOxNy under visible light irradiation.