Efficient deposition technique for diamond-like carbon coatings

The favored method to prepare diamond-like (DLC) coatings is the radio frequency (r.f./13.56 MHz) plasma enhanced CVD (PECVD) working with hydrocarbon gases. Working gas pressures typically range from 0.5 to 2 Pa. However, it is difficult to scale up r.F. deposition arrangements. Furthermore the costs for the necessary r.f. generators are rather high. To overcome these problems we used so called mediumfrequency (m.f.) discharges (some 10 to 300 kHz) for plasma generation. Both, harmonic a.c. and pulsed d.c. voltages were used to excite the plasma. DLC deposition could be carried out in the above mentioned pressure range as well as at higher pressures up to some 100 Pa. The quality of the films, especially with respect to wear and friction was the same as that of r.f. plasma prepared DLC films. Some examples and coating applications will be reported.