Microstructures, mechanical and tribological properties of NbN/MoS2 nanomultilayered films deposited by reactive magnetron sputtering

The NbN/MoS2 nanomultilayered films with different thickness of MoS2 were synthesized by reactive magnetron sputtering. The influences of MoS2 thickness on microstructures, mechanical and tribological properties were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscope (SEM) and nano-indentation techniques. The results indicate that the NbN/MoS2 nanomultilayered films are composed of NbN phase with (111) preferred orientation. As the thickness of MoS2 layer increases, the crystallinity of NbN phase initially improves and then deteriorates, and the hardness and elastic modulus first increases and then decreases. When the thickness of MoS2 layer is 0.8 nm, the hexagonal-structured MoS2 layers transform to B1-NaCl structure under the template effect of NbN layers and grow epitaxially with NbN layers, resulting in enhancement of hardness and elastic modulus. The maximum hardness and elastic modulus reach 30.4 GPa and 431 GPa, respectively, which are remarkably higher than those (22.8 GPa and 354 GPa) of NbN monolithic film deposited under the same conditions. The friction coefficient of NbN/MoS2 nanomultilayered films are in a range of 0.20-0.30, much lower than that of the monolithic NbN film.