Tribological properties of hard a-C:H:F coatings

Abstract Hydrogenated amorphous carbon thin films containing fluorine (a-C:H:F) have been produced by radio-frequency plasma enhanced chemical vapor deposition by using different F/H ratios in the gas phase. The introduction of fluorine from 0 to 19 at.% resulted in a decrease of hydrogen content and to the formation of C F and C F 2 bonds. For all the films, Raman analysis showed a typical diamond-like carbon response with an evolution of the structure to larger sp 2 clusters with less hydrogen while fluorine content increased. The drop in hardness generally observed in the literature with fluorine introduction was less abrupt here: for a fluorine content up to 6.5 at.%, the measured hardness was 28 GPa, and for 19 at.% of fluorine, value was 20 GPa. These are quite high values for a-C:H:F thin films. Moreover, fluorine improved tribological behavior in dry conditions with friction coefficient slightly reduced at low fluorine content and wear rate significantly reduced: divided by two to four than the fluorine free reference coating.