Plasma polymerization of CF 4 + H 2 mixtures on the surface of polyethylene and polyvinylidene flouride substrates

Abstract

A non-equilibrium low pressure plasma was established in a bell-jar type reactor with a corona discharge configuration of electrodes (hollow blade electrode-grounded cylinder) at a low pressure (150 Pa), with a 70 kHz excitation source, for the plasma polymerization of CF 4 + H 2 mixtures on polyethylene (PE) as well as on the flourine-containing substrate material polyvinylidene flouride (PVDF). The effect of the feed composition, treatment time and the nature of the substrate both on the chemical structure of the deposited film and on the growth mechanism were analysed. In particular, it was found that the structure of the film was highly dependent on the hydrogen concentration in the feed and on the treatment time. Furthermore, it became clear that the polymerization rate on a PE substrate decreased with increasing treatment time and that the flourine constituent in a PVDF substrate participated in the etching processes. Therefore, as compared with a PE substrate, a higher concentration of hydrogen in the CF 4 + H 2 mixtures is needed to form a polymer on a PVDF substrate.