The equilibrium phase diagram of mo

The equilibrium phase diagram of molybdenum-nitrogen proposed by Jehn, enriched by computed phases of nonstoichiometric transition metal nitrides Mo3N2, shows three stable phases: the tetragonal β-Mo2N phase at low temperature, the cubic γ-Mo2N phase stable at high temperature and the hexagonal δ-MoN phase up to 50 at.% nitrogen concentration. Using non-equilibrium processes, the phase structure of Mo-N coatings depends on the deposition technology, and mainly on the pressure of nitrogen in the working chamber and the substrate bias voltage. Ihara et al. report also on the existence of a cubic ζ-MoN phase. While this phase is thermodynamically unstable, a stabilization can be achieved using non-equilibrium techniques such as R.F. sputtering in high nitrogen partial pressure, nitrogen ion implantation, or low energy ion assisted deposition. The mechanical properties of the molybdenum nitride coatings are firmly dependant on the nitrogen pressure in reactive sputtering. The ζ-MoN phase is predicted to have the highest superconducting temperature among all refractory binary carbides and nitrides with Tc =29.4 K. However, a narrow set of parameters provide an incomplete and misleading results, so more information about the material structure and applicability can be gained by mechanical testing.