ION-INDUCED RADICAL PRODUCTION ON SURFACES DURING DEPOSITION OF HYDROGENATED AMORPHOUS-CARBON

In a methane/argon discharge used for deposition of hydrogenated amorphous carbon (a-C@B: H), energetic ion bombardment yields radicals on solid surfaces by two mechanisms: (i)fragmentation of hydrocarbon ions at their impact on the surface and (ii)sputtering of the already deposited a-C:H film. To discriminate between these two mechanisms, the emission intensity of CH(A-X) in the vicinity of a negatively biased electrode was measured as a function of the ion impact energy. The threshold energy for yielding the excited CH radical was found to be ∼2 eV for fragmentation and ∼80 eV for sputtering. The fragmentation yield is much larger on a metal surface than on a-C:H layer. The sputtering yield dominates over the fragmentation yield for the high impact energy(>150 eV).