Surface modification of materials by dielectric barrier discharge deposition of fluorocarbon films

Dielectric barrier discharges have been used to deposit fluorocarbon (FC) films on various materials, such as paper, glass, and silicon substrates. The primary monomers used for plasma polymerization were difluoromethane (CH2F2), octafluoropropane (C3F8), and octafluorocyclobutane (C4F8). FC films were characterized using Fourier transform infrared spectroscopy, atomic force microscopy, static contact angle measurements, and scanning electron microscopy. Surface and structural properties of deposited films are strongly dependent on the plasma compositions and plasma parameters. FC films deposited on paper are to enhance its barrier properties and to achieve hydrophobic surfaces. Contact angle studies reveal that a minimum FC film thickness of about 200 nm on paper is required to completely cover surface and near-surface fibers, thereby providing the paper with long term hydrophobic character. In the C3F8 and C4F8 systems, the contact angles of the deposited films do not change appreciably with plasma parameters and are strongly dependent on the substrate roughness. Hydrogenated FC films deposited with CH2F2 plasmas show the relatively low contact angles due to the existence of CHX (x = 1-3) groups.