handbook of carbon, graphite, diamond and fullerenes

346 Carbon, Graphite, Diamond, and Fullerenes
3.3 DLC by PVD-CVD Process from a Hydrocarbon Source
In the PVD-CVD process, the carbon source is a hydrocarbon gas
instead of the solid carbon target of the purely PVD process. The same
activation methods (ion-beam sputtering, laser, glow-discharge, or others)
are used but a-C:H is deposited instead of a-C.
Deposition by RF Activation. A common activation method is a
high-frequency RF gas discharge (13.56 MHz), generated in a mixture of
hydrogen and a hydrocarbon such as methane (CH4), n-butane (C4H10), or
acetylene (C2H2). A diagram ofthe equipment is shown in Fig. 14.5 J 17 ' Two
factors, the asymmetry of the electrodes and the considerable difference in
mobilities between electrons and ions, cause the spontaneous generation
of a negative potential at the substrate which, as a result, is bombarded by
the ionized gas species.
Gas Manifold
fit
1 1
RF
Generator
Work
^~ Piece
Vacuum
Pump
~ Matchbox
Figure 14.5. Schematic of apparatus for the deposition of a-C:H DLC.' 17 '