Influence of Oxygen Flow Rate on the Properties of FeOXNY Films Obtained by Magnetron Sputtering at High Nitrogen Pressure

Fe-O-N films were successfully deposited by magnetron sputtering of an iron target in Ar-N-2-O-2 reactive mixtures at high nitrogen partial pressure 1.11 Pa (Q(N-2) = 8 sccm) using a constant flow rate of argon and an oxygen flow rate Q(O-2) varying from 0 to 1.6 sccm. The chemical composition and the structural and microstructural nature of these films were characterized using Rutherford Backscattering Spectrometry, X-ray diffraction, and Conversion Electron Mossbauer Spectrometry, respectively. The results showed that the films deposited without oxygen are composed of a single phase of gamma"-FeN, whereas the other films do not consist of pure oxides but oxidelike oxynitrides. With higher oxygen content, the films are well-crystallized in the alpha-Fe2O3 structure. At intermediate oxygen flow rate, the films are rather poorly crystallized and can be described as a mixture of oxide gamma-Fe2O3/Fe3O4. In addition, the electrical behavior of the films evolved from a metallic one to a semiconductor one, which is in total agreement with other investigations. Comparatively to a previous study carried out at low nitrogen partial pressure (0.25 Pa), this behavior of films prepared at higher nitrogen partial pressure (1.11 Pa) could be caused by a catalytic effect of nitrogen on the crystallization of the hematite structure.