Iron nitride thin films deposited by chloride assisted plasma enhanced chemical vapour deposition: facile stoichiometry control and mechanism study

A facile method for iron nitride thin film preparation by the plasma enhanced chemical vapour deposition technique using FeCl2, N-2 and H-2 as starting materials was developed. Iron nitride thin films with different phase structures, including three stoichiometric phases (gamma'-Fe4N, epsilon-Fe3N and zeta-Fe2N) and solid solutions in between could be prepared by this method. Variation of N-2 or H-2 flow, plasma power or FeCl2 evaporation temperature allowed continuous adjustment of the film stoichiometry. Typical deposition rates of 10-20 nm min(-1) was achieved in typical conditions, much faster than that in most conventional low pressure thin film fabrication methods. This method was also successfully applied to prepare the nitrides of Mn, Co and Ni by simply replacing FeCl2 with the corresponding metal chlorides. The mechanisms determining film stoichiometry and deposition rate were interpreted by a simple chemical model together with optical emission spectroscopy diagnostics of plasma.