Growth of iron nitride thin films by molecular beam epitaxy

Iron nitride films were grown by atomic-nitrogen-assisted molecular beam epitaxy. ZnS-type FeN (γ″-FeN) was synthesized with low Fe evaporation rates (≤ 0.2 Å/s) at low growth temperatures below 210 °C whereas γ′-Fe4N was synthesized with high Fe evaporation rates (≥1.0 Å/s) at 130-415 °C. Our results indicate that the stabilization of ZnS-type FeN requires not only the fulfillment of thermodynamic constraints but also the control of a delicate balance of kinetically driven competition. The use of lattice-matched GaN(0001) substrates enables the growth of epitaxial films of ZnS-type FeN.