Nitrogen redistribution in annealed LaFeOxNy thin films investigated by FTIR spectroscopy and EELS mapping

LaFeOxNy thin films have been deposited by magnetron sputtering in Ar/O2/N2 gas mixture at 800°C. Such oxynitride perovskites present an uncommon infrared vibration mode position at 2040cm-1, due to presence of nitrogen, which disappears with heating in air. The evolution of this vibration mode with temperature has been studied and permit to determine an activation energy of thermal degradation of LaFeOxNy. The quantification of nitrogen by Elastic Recoil Detection Analysis (ERDA) before and after heating exhibits the same nitrogen content, indicating a redistribution of nitrogen. Such nitrogen redistribution is observed by Electron Energy Loss Spectroscopy (EELS) mapping, showing migration of nitrogen into grain boundaries, in association with film oxidation.