Evaluation of deposition conditions to design plasma coatings like SiOx and a-C:H on polymers

RF excited gas discharges of hexamethyldisiloxane (HMDSO) with and without oxygen and methane (CH4) without further carrier gas were examined to identify reaction parameters determining deposition rate and film properties of SiOx and a-C:H films, respectively. This evaluation is supported by the used reactor type which enables well-defined deposition conditions. Both symmetrical and asymmetrical electrode configurations are investigated. It is found that the deposition rate depends on the reaction parameter power input per gas flow where the gas flows of monomer and reactive carrier gases are added. Thus, O2 in conjunction with HMDSO can be considered as a film-forming gas. Even in asymmetrical discharges the concept of the reaction parameter W/F holds, as long as the increasing ion bombardment allows a continuous film growth. While W/F controls the chemical composition of the films, the potential drop across the plasma sheath influences the mechanical film properties. With these findings SiOx and a-C:H plasma coatings can be designed.