ABSTRACT
Thin films of tetraethoxysilane (TEOS) and tetraethylsilane (TES) were plasma-polymerized in an RF glow-discharge and deposited on polyethylene terephthalate) (PET) and stainless steel (SS) substrates. Changes in composition were studied as a function of various parameters including the nature of the monomer and different deposition conditions, among them, the flow-rate of oxygen used as carrier gas. Particular emphasis was placed on the carbon content which allows modifying the physical and mechanical characteristics of the so-formed SiOxCy films by passing from organic-like to inorganic-like materials. Chemical characterization was carried out by low-energy electron induced X-ray spectroscopy (LEEIXS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Permeation properties toward water vapor were studied for films containing 65, 33 and 6 at.% carbon deposited on PET substrates 25 μm in thickness. Good barrier properties against water vapor permeation were obtained for polymer-like films (containing 33 or 65 at.% carbon) since improvement factors in the range 100–400 were determined for films 200–500 nm in thickness. Furthermore, coating adhesion was evaluated using a fragmentation test for films deposited on PET substrates and a three-point flexure test for films deposited on SS substrates. In both cases, the best adhesion performances were observed for polymer-like films due to their intrinsic flexibility.
