Mössbauer characterization of reactively sputtered iron nitride films

We have shown by Mössbuaer spectroscopy and x-ray diffraction that single-phase, small crystallite size films in the Fe–N system (γ′-Fe4N and Fe3N) can be synthesized by varying reactive sputtering conditions in Ar+N2 gas mixtures. The γ′-Fe4N phase can be further produced and controlled by addition of H2 to the sputtering gas with single phase films (i.e., no unreacted α-Fe present) obtained only at a 1:3 N2:H2 mixture. The film microstructures are consistent with the structure zone model classification scheme and show that faceted, high surface area, single phase γ′-Fe4N and Fe3N films can be prepared with crystallite sizes of ∠400–500 Å.