Low-temperature gaseous nitriding and subsequent oxidation of epitaxial Ni/Fe bilayers

Low-temperature gaseous nitriding was applied to epitaxial Ni/Fe bilayers deposited onto a MgO(001) substrate. The pore-free nitride layers produced were subsequently oxidized in oxygen. The samples were analyzed by conversion electron Mossbauer spectroscopy (CEMS), x-ray diffraction (XRD), and Rutherford backscattering spectroscopy in combination with channeling techniques. Nitriding in pure NH3 gas at 300 degrees C led to the formation of a textured E-Fe-nitride layer with a predominant composition of Fe2.07N. The epitaxial relationship of the E-Fe-nitride layer with the MgO substrate was found to be epsilon-Fe2.07N{203}(010)//MgO(001)(110). The nitride layer produced was subsequently oxidized in p(O-2) = 100 mbar at 275 degrees C. While the XRD spectra acquired on the oxidized samples revealed the formation of a Fe-oxide phase with a spinel structure, the GEMS spectral lines could not be interpreted in terms of any Fe-oxide or Fe-hydroxide phase know. It is suggested that the peculiarities in the GEMS data are caused by N atoms incorporated into the oxide lattice