Magnetron Sputtering of Transition Metal Oxynitrides and Their Characterization with Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy

Abstract

Transition metal oxynitrides are of growing interest for their use as electrocatalyst for nitrogen reduction reaction. The metals in the oxynitride used for catalytic process are stabilized in intermediate state for effective activation of nitrogen. Therefore, studying the interaction of metal oxynitrides films to ambient exposure is necessary. Here, sputter deposited vanadium oxynitride is compared to cobalt oxynitride using insitu Auger electron spectroscopy (AES), ex situ X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). After deposition in Ar/N2 environment, in situ AES spectra indicate that film is vanadium oxynitride despite oxygen is not the reactive gas. In contrast, in situ AES indicate film is pure cobalt nitride at the same base pressure and deposition condition (as vanadium). For ambient exposure, in situ AES indicate the incorporation of oxygen in the cobalt nitride film to form cobalt oxynitride. Ex situ XPS indicate both films get more oxidized but uniformly distributed as there is only slight difference in grazing and normal emission XPS. XRD and SEM also indicate how homogeneously distributed both films are. These finding confirms how important it is that transition metal centers are kept in intermediate oxidation state for the activation of nitrogen bond.