Using ammonia for reactive magnetron sputtering, a possible alternative to HiPIMS?

While most of the works devoted to the synthesis of transition metal nitride coating by magnetron sputtering use N₂ as reactive gas, an alternative method is proposed, namely using ammonia (NH₃) as reactive gas. The magnetron sputtering of chromium in Ar/NH₃ atmosphere is studied and compared to Ar/N₂ atmosphere, with in situ (hysteresis curve, target voltage measurement, optical emission spectroscopy, deposition rate) and ex situ characterizations (XPS, XRD, SEM, RBS, UV–Vis, nanoindentation, 4-points probe). It appears that ammonia as a reactive gas influences the optical, electrical and mechanical properties as well as the microstructure of the thin films in a very similar way to HiPIMS with N₂ reactive gas; improved mechanical properties are obtained, attributed to a change of the morphology, from columnar-like to nanocrystalline.