Microstructure and tribological properties of the a-C:H films deposited by magnetron sputtering with CH4/Ar mixture

►The a-C:H films deposited by magnetron sputtering with CH4 have low internal stress (<1 GPa). ►The CH4/Ar ratio plays an important role in the H content but acts a little function on the sp3/sp2 ►The fraction of sp3 C alone is not a reliable estimate of the film structure or properties. ►The film with dense structure and moderate sp3 C-C/sp3 C-H has the best tribological properties.