Structural investigations of iron oxynitride multilayered films obtained by reactive gas pulsing process

Multilayered Fe-O-N films were deposited on glass and silicon substrates using reactive magnetron sputtering with a reactive gas pulsing process. The argon and nitrogen flow rates were kept constant during sputtering of a pure iron target while the oxygen flow rate was pulsed during deposition. To determine the film composition, Rutherford backscattering spectrometry was used. X-ray diffraction revealed the formation of a face-centered cubic (fcc) structure with a lattice parameter close to that of γ″′-FeN. In addition, traces of iron oxide Fe1 − xO (wüstite) have been detected in some films. Transmission electron microscopy provides clear evidence for the formation of a multilayer structure for all the coatings. Electron energy loss spectroscopy was used to check that each layer contains both nitrogen and oxygen. The local environment of iron atoms studied by 57Fe Mössbauer spectrometry at 300 K indicated that the samples consist mainly of an iron oxynitride phase with a NaCl-type structure where oxygen atoms partially substitute nitrogen ones. However, in accordance with the X-ray diffraction results, a small amount of iron nitride (FeN) and oxide (Fe1 − xO) is also present in the nitrogen-rich and oxygen-rich layers, corresponding to the sputtering time (toff) and (ton). Thus the hypothesis of a multilayer structure, type (γ″′-FeN/Fe1 − xO) can be excluded because the spectra Mössbauer always reveal the presence of iron oxynitride.