Microstructure and properties of DLC/CNx films with different CNx sublayer thicknesses.

The DLC/CN x multilayer films with different CN x sublayer thicknesses were deposited on Si wafer by using magnetron sputtering technique. The microstructure and properties of the films were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nano-indentation, scratch tests and a ball-on-disc tribometer. All the DLC/CN x films were amorphous and compact with low internal stresses and strong reinforcement effects. The content of sp 3 bonds in CN x sublayer, the hardness and adhesion of the overall films decreased while the wear rate of the multilayer films increased with increasing the CN x sublayer thickness. The friction states of the multilayer films in vacuum and air were very stable. The friction coefficients of the DLC/CN x films were ~0.16 in vacuum and ~0.20 in air, and they were independent of CN x sublayer thickness. The multilayer film with CN x sublayer thickness of 0.5 nm was of a hardness of 36.9 GPa and interface adhesion of 27 N, which exhibited excellent tribological properties in vacuum and in air. • DLC/CN x multilayers with thin CN x sublayer were prepared. • A strong interface strengthening effect was observed in the films. • Microstructure of CN x sublayer was related to its thickness. • Multilayers exhibited better tribological properties than DLC in vacuum and in air. [ABSTRACT FROM AUTHOR]