Industrial applications based on plasma polymerization require reliable processes that can be transferred to production‐scale reactors. To enable an inexpensive access to control plasma deposition processes, macroscopic kinetics were investigated to describe plasma polymerization, which is based on the concept of chemical quasi‐equilibrium. The evaluation of deposition rates was carried out in order to obtain the apparent activation energy for a specific process. Influencing factors, such as substrate temperature, energetic particles, reactor geometry, plasma expansion, pressure, monomer, carrier/reactive gas, power modulation, and plasma source were thoroughly examined. The obtained activation energy was correlated to the plasma‐chemical processes, such as dissociation and radical formation, which are taking place within the active plasma zone. Since these processes are also contributing to the film growth, the activation energy was used for the scale‐up of plasma polymerization processes.

To perform a systematic study over a broad parameter range of acrylic acid discharges, we varied the energy input W/F over a wide range. Five different regimes could be identified (from low to high energy input): regime I, where oligomerization takes place; regime II, the radical‐dominated plasma polymerization of acrylic acid; regime III, a transition regime showing etching/oxidation effects; regime IV, where the plasma polymerization resembles the one observed for CO2/C2H4 discharges; and regime V, where etching effects yield a reduction in deposition rate. These results show that the polymerization mechanism can be described as a function of the energy input W/F. Specifically, a parameter range where acrylic acid can be replaced by CO2/C2H4 discharges has been identified.magnified image

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Functional plasma polymers were deposited from pure ethylene discharges and with the addition of carbon dioxide or ammonia. The incorporation of oxygen and nitrogen-containing functional groups depends on the fragmentation in the gas phase as well as on the densification during film growth. While a minimum energy per deposited carbon atom is required for cross-linking, the densification and accompanying reduction of functional group incorporation was found to scale linearly with momentum transfer through ion bombardment during film growth.

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Plasma polymer coatings with embedded Ag nanoparticles were deposited in a low pressure RF plasma reactor using an asymmetrical setup with an Ag electrode. The plasma polymer was deposited from a reactive gas/monomer mixture of CO2/C2H4 yielding a functional hydrocarbon matrix. In addition, Ar was simultaneously used to sputter Ag atoms from the Ag electrode, forming nanoparticles within the growing polymer matrix. The influence of the power input, gas ratio and coating thickness on both, the Ag content and the Ag nanoparticle morphology, as well as the distribution in the polymer matrix were investigated. It was found that both increasing the power input and the CO2 ratio result in a higher incorporation of Ag into the matrix.

Functional hydrocarbon plasma polymer coatings were investigated using a low pressure RF plasma reactor. The deposition rate was examined for different CO2/C2H4 gas ratios and different power inputs at constant pressure. The CO2/C2H4 ratio can be used to tailor the functionality and the permanence of the plasma polymer coatings which is shown by XPS. The deposition of these plasma polymer coatings was compared in a symmetrical and asymmetrical setup of the reactor and discussed regarding energy input and plasma sheath potential for the varying plasma conditions. Furthermore, the influence of Ar admixture was examined in order to identify sputtering conditions by using an asymmetric Ag electrode. While a drop in the absolute deposition rate can be seen for Ar added in symmetrical conditions, the asymmetrical setup showed no noticeable differences.magnified image