Microstructures and mechanical properties of MoNx isomeric multilayer films with different number of layers deposited by DC magnetron sputtering

In order to improve the mechanical properties of Mo2N films, MoNx isomeric multilayer films with Mo2N as the surface layer were prepared using DC magnetron sputtering by alternately stacking Mo2N deposited at 0.5 Pa and mixture of Mo3N2 and Mo5N6 deposited at 1.2 Pa. The microstructures and mechanical properties of films were investigated by X-ray diffraction, field emission scanning electron microscope, atomic force microscope and nanoindenter. With the increase of the number of layers, the surface particle size of multilayer films increases gradually, and the interface of multilayer films becomes much sharper. The average roughness, hardness and friction coefficient of films first decrease from 3.85 nm, 24 GPa, and 0.08 of Mo2N monolayer film to 2.83 nm, 18 GPa and 0.04 of six-layer film, and then increase to 3.45 nm, 19.8 GPa and 0.05 of ten-layer film, respectively. The Young's modulus of films decreases gradually from 289 GPa of Mo2N monolayer film to 222 GPa of ten-layer film. The critical load (Lc) of films decreases gradually from 24 mN of Mo2N monolayer film to 4 mN of ten-layer film. The changes in the performance of MoNx isomeric multilayer films are mainly attributed to the change in the microstructure of the films caused by the number of layers. [Display omitted]