Reactive magnetron sputter deposition of polycrystalline vanadium nitride films

Polycrystalline vanadium nitride films were deposited onto M2 steel substrates using a high-rate reactive dc magnetron sputtering system by sputtering vanadium metal in an Ar+N2 atmosphere under N2 partial pressure control. The crystal structure, surface morphology, and properties of the films were affected by several process parameters such as nitrogen partial pressure, target power, and negative substrate bias. Analytical techniques including x-ray diffraction and scanning electron microscopy were used to characterize the structure and morphology of the films, and the mechanical properties of the films were measured by a Vickers microhardness and a scratch adhesion testers. The nitrogen partial pressure was found to be the dominant deposition parameter for the formation of different phases which includes crystalline V metal, hexagonal β-V2Nx, and cubic δ-VNx, amorphous V–Nx solid solution, and their mixtures. The film hardness was affected by crystalline phase, and a maximum hardness of 3000 kgf/mm2 Hv0.05 was found at the β-V2Nx phase. The morphology of the films varied in a wide range from cauliflowerlike rough and porous surface to smooth and dense surface, and can be correlated to deposition parameters.