Growth and characterization of epitaxial iron–nitride thin films

• Alpha phase (α″-Fe16N2) has been obtained in its highest concentration (36%) in the sample.
• Epsilon paramagnetic phase (ε-Fe2.1N) has been obtained with 100% purity.
• Gamma phase (γ″-FeN phase) with N concentration in the phase diagram of 50% has been obtained and the production of this phase was worked out.
• The knowledge of the studied iron-nitride phases in the phase diagram can be extended.

Many of the Fe–nitride phases have been studied in much detail. Nevertheless there is still a debate on the most efficient, exact and controlled way of obtaining thin films of the desired iron nitrides phases. We present the recent state of our research focusing on the low and high nitrogen-iron phases and transformations between them due to irradiation, temperature and time exposure. Thin films of iron nitrides were deposited by Molecular Beam Epitaxy in Ultra High Vacuum conditions. We grew films of the FeN alpha (α″-Fe16N2), epsilon (ε-FexN, 2 ⩽ x ⩽ 3) and gamma (FeNy, y > 0.5) phases. By changing the parameters of growth conditions we tried to obtain the α″-phase in its possible purest form. We grew the ε-phase mainly in a nonmagnetic form. We worked also on iron mononitride FeN, which is known to exist in different phases. There is a debate on the exact crystal structure and the coexistence of these phases. On the basis of room temperature Conversion Electron Mössbauer Spectroscopy analysis accompanied with Rutherford Backscatering Spectroscopy spectra we show our results on the growth and transformations of the samples under different conditions.