Ion-induced surface activation, chemical sputtering, and hydrogen release during plasma-assisted hydrocarbon film growth

Abstract

Synergisms between different species emerging from hydrocarbon plasmas can enhance the chemisorption of radicals at the surface of a growing film. It has been shown that the rate of CH3 chemisorption can be increased by a simultaneously incident flux of ions or H atoms; the latter species cause the formation of surface dangling bonds, which serve as preferred adsorption sites for incoming CH3. These synergisms can, however, be counteracted by erosion processes due to the same species. The interplay between the enhancement of film growth by ion/H atom assisted chemisorption and simultaneous erosion processes is investigated in a particle-beam experiment. An a-C:H film is exposed to three individually controllable quantified particle beams—ions, CH3, and atomic hydrogen. The data can be consistently explained if we include two effects counteracting ion- or H-induced chemisorption: (i) recombination of neighboring dangling bonds and (ii) the occurrence of chemical sputtering in case of an intense H flux. Finally, the balance between H incorporation and ion-induced hydrogen release is investigated. The latter process can be compensated by incident thermal hydrogen atoms as long as the ion range inside the film does not exceed the range of the hydrogen atoms.