Oxynitride perovskite LaTiOxNy thin films deposited by reactive sputtering

This paper reports on the first study of structural and optical properties of reactively RF-sputtered lanthanum titanium oxynitride thin films using an original oxynitride LaTiO₂N target and an argon–nitrogen mixture as reactive plasma. The depositions were carried out by varying the process parameters such as RF power, total pressure, argon and nitrogen rates and substrate temperature. Wavelength dispersive spectrometry (WDS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–visible spectroscopy show that titanate lanthanum oxynitride compounds can exist as a domain composition, LaTiO_xN_y. Films prepared in pure argon are oxide films, transparent, amorphous and insulating. Polycrystalline and 001]-textured oxynitride thin films, with different nitrogen contents, can be deposited on SrTiO₃ substrates, depending on the sputtering conditions. As expected, the introduction of nitrogen in the coatings leads to a band gap narrowing. Oxynitrides' thin films are thus coloured and semiconductive.