Synthesis and characterization of single-phase epitaxial Cr₂N thin films by reactive magnetron sputtering

Cr₂N is commonly found as a minority phase or inclusion in stainless steel, CrN-based hard coatings, etc. However, studies on phase-pure material for characterization of fundamental properties are limited. Here, Cr₂N thin films were deposited by reactive magnetron sputtering onto (0001) sapphire substrates. X-ray diffraction and pole figure texture analysis show Cr₂N (0001) epitaxial growth. Scanning electron microscopy imaging shows a smooth surface, while transmission electron microscopy and X-ray reflectivity show a uniform and dense film with a density of 6.6 g cm^-3, which is comparable to theoretical bulk values. Annealing the films in air at 400 °C for 96 h shows little signs of oxidation. Nano-indentation shows an elastic-plastic behavior with H = 18.9 GPa and E _r = 265 GPa. The moderate thermal conductivity is 12 W m^-1 K^-1, and the electrical resistivity is 70 μΩ cm. This combination of properties means that Cr₂N may be of interest in applications such as protective coatings, diffusion barriers, capping layers and contact materials.