Microstructure and mechanical properties of carbon nitride multilayer films deposited by DC magnetron sputtering

Carbon nitride (CNx/CNx) multilayers with sequential sp3-rich and sp2-rich layers were deposited on c-Si substrate by direct current magnetron sputtering. The composition, microstructure and morphology of the films were investigated by the X-ray photoelectron spectroscopy and transmission electron microscopy. In the films, the sp3 C–N rich and the sp2 C–N rich layers exhibit amorphous feature and graphite-like structure, respectively, and the multilayered structure is continuous over relatively well defined and smooth layer interfaces. The mechanical properties of the films were measured by the nanoindentation and nanoscratch tests. The multilayer films showed lower compressive stress and higher hardness than their monolayer components. Meanwhile, the a-CNx multilayer film with a bilayer period of 60 nm exhibited the improved mechanical properties, and the lowest friction coefficient and the highest wear resistance.