Direct identification of the synergism between methyl radicals and atomic hydrogen during growth of amorphous hydrogenated carbon films

The simultaneous interaction of methyl radicals (CH3) and atomic hydrogen (H) with the surface of amorphous hydrogenated carbon (a-C:H) film is investigated. Two identical quantified beam sources for H and CH3 are used. The growth and/or erosion during the simultaneous interaction of the two beams with an amorphous hydrogenated carbon film is monitored by using in situ real-time ellipsometry at a substrate temperature of 320 K. Interaction with the CH3 beam alone causes slow growth, corresponding to a sticking coefficient for CH3 of ∼3×10−5. Simultaneous interaction of the atomic hydrogen beam and the CH3 radical beam yields a sticking coefficient for CH3 of 3×10−3, which is two orders of magnitude larger than for CH3 alone. From a microscopic modeling of this synergistic growth, the reaction probability for CH3 adsorbing at an adsorption site, which is created by atomic hydrogen at the surface, is derived to be 0.14.