Plasma assisted thin film formation

Abstract

Thin films of fluorocarbon-based polymers can be deposited by plasma assisted polymerisation of various perfluorocarbons. The chemical natures of plasma polymers of hexafluoropropene and perfluorohexane were examined as a function of power, flow rate and position in reactor. Polymerised hexafluoropropene displayed increased fluorine contents at high powers; this is at odds with perfluorohexane which demonstrated lower fluorine contents. Differing reaction mechanisms between saturated and unsaturated perfluorocarbons were proposed to explain this. Both perfluorocarbons were found to give increased CF(_2) contents out of the plasma glow region. This was demonstrated to be a function of distance from the monomer inlet, and was ascribed to the production of long lived polymer forming species in the gas phase. Plasma oxidation of low density polyethylene, polystyrene and poly (ether ether ketone) with oxygen and carbon dioxide was modelled by corresponding photooxidation reactions. Correlations between the structure of the polymer, the treatment used, and the final products were drawn. Aliphatic components tended to give carbon-oxygen single bonds, phenyl rings were oxidised to carbonyl and acid groups, and carbonyl groups to acids. Metal-containing polymeric thin films were produced from plasmas of zinc acetylacetonate and aluminium tri-sec -butoxide. The products from each monomer were different, with the zinc compound resulting in a high proportion of zinc carboxylate and the aluminium compound giving the oxide or hydroxide. Incorporation of these compounds into a perfluorohexane plasma resulted in the formation of metal fluoride containing thin films.