TEM characterisation of GdN thin films

Abstract

The rare-earth metal nitrides have been predicted to possess a wide range of electronic structures, ranging from ferromagnetic to halfmetallic to semiconducting, which makes these materials attractive for a range of applications. In this study, GdN thin films were grown at room temperature on silicon and glass quartz substrates by thermally evaporating gadolinium metal in nitrogen atmospheres. A detailed microstructural characterisation of these films was carried out using a variety of techniques such as transmission electron microscopy (TEM), Rutherford backscattering spectroscopy (RBS) and energy dispersive X-ray spectrometry. TEM analysis indicated the films are nano-crystalline, with crystallite sizes being affected by the ionisation state of the nitrogen atmosphere used. Sources of the films’ internal stress were discussed with a significant amount of oxygen absorption, identified by RBS, being a probable cause. Electron diffraction and energy dispersive X-ray studies found that GdN was the only phase present with oxygen uniformly distributed throughout the film.