Influence of gas phase and surface reactions on plasma polymerization

The formation of plasma polymers is based on multistep reactions that are taking place both in the gas phase and on the surface of the growing film. In order to gain more insights and to control plasma polymerization processes, some assumptions can be made that allow a macroscopic description. Following this idea, a concept was developed based on the energy input both into the gas phase (plasma) and during film growth (surface) that helps in up-scaling plasma polymerization processes. In order to test this concept, various a-C:H:N thin films were deposited under different NH3/C2H4 gas ratios, power inputs W, and gas flow rates F. Thereby, the energy consumed in the gas phase is controlled by W/F yielding a flux of film-forming species. The comparison of two comparable plasma reactors of different sizes indicate that while the reaction parameter W/F plays a major role for the transfer of plasma polymerization processes, the energy input into the film by ion bombardment during film growth should also be taken into account.