Compositional study of δ-NbN film by Auger electron microscopy

The chemical stoichiometry on the surface of superconducting δ-NbN thin films is of great importance for their application. Here, we fabricated the δ-NbN thin films on SiO 2 /Si substrate by DC sputtering method. The film was characterized using X-ray diffraction (XRD) and atomic force microscopy (AFM). Transport properties were measured to reveal the field dependent superconducting transition temperature. Both XRD and electrical measurement show high crystallinity of δ-NbN phase. A homogeneous and smooth surface morphology was measured by AFM. Auger electron spectroscopy (AES) was applied to analyze the composition along the depth of the film. The evolution of Auger peak profile, heights and nitride stoichiometry at the film surface is discussed. The current study provides a more thorough understanding of complex chemical compositions of δ-NbN thin films.