Structure and chemical composition of polymer films deposited in a dielectric barrier discharge (DBD) in Ar/fluorocarbon mixtures

The properties of fluorocarbon polymer films deposited on Si wafers, foils, and technical textiles in a DBD at atmospheric pressure have been studied. Fourier transform infrared (FTIR) absorption spectroscopy and X-ray photo electron spectroscopy (XPS) were applied to get information on the atomic content and structure of the deposited polymer films in dependence on fluorocarbon molecules CF4, C2F6, C3HF7, C2H2F4, C3F8 and c-C4F8. Analysis of the XPS-spectra indicates that polymer films can be deposited if the F/C ratio of the starting fluorocarbon molecules is smaller, or close to 3. FTIR-absorption spectra of films on Si wafers show an “amorphous” film structure with the main absorption peak of CF2-groups at 1200 cm−1. By variation of the F/C ratio it could be shown that plasma polymerisation correlates strongly to the appearance of an “amorphous” PTFE absorption peak at 740 cm−1 in the FTIR-absorption spectra in the DBD. H-atoms in the starting fluorocarbon molecules as well as admixture of hydrogen influence the cross linking effects in the film during plasma polymerisation process.