Influence of N₂ Gas Flow Ratio and Working Pressure on Amorphous Mo-Si-N Coating during Magnetron Sputtering

In this study, Mo-Si-N coatings were deposited on Si wafers and tungsten carbide substrates using a reactive direct current magnetron sputtering system with a MoSi powder target. The influence of sputtering parameters, such as the N-2 gas flow ratio and working pressure, on the microstructure and mechanical properties (hardness (H), elastic modulus (E), and H/E ratio) of the Mo-Si-N coatings was systematically investigated using X-ray diffractometry (XRD), scanning electron microscopy (SEM), nanoindentation, and transmission electron microscopy (TEM). The gas flow rate was a significant parameter for determining the crystallinity and microstructure of the coatings. A Mo2N crystalline coating could be obtained by a high N-2 gas flow ratio of more than 35% in the gas mixture, whereas an amorphous coating could be formed by a low N-2 gas flow ratio of less than 25%. Furthermore, the working pressure played an important role in controlling the smooth surface and densified structure of the Mo-Si-N coating. For the amorphous Mo-Si-N coating deposited with the lowest working pressure (1 mTorr), the hardness, elastic modulus, and H/E ratio reached from 9.9 GPa, 158.8 GPa, and 0.062 up to 17.9 GPa, 216.1 GPa, and 0.083, respectively.