ADHESION OF A THIN SILICON-OXIDE FILM ON A POLYCARBONATE SUBSTRATE

The present paper analyzes the adhesion mechanisms of a silicon oxide film on a polycarbonate substrate, combining XPS, UV-visible ellipsome try and Fourier transform infrared phase-modulated ellipsometry (FTPME ) measurements. In particular, we present the new FTPME technique: Due to its submonolayer sensitivity to vibrational properties, it suits w ell to physico-chemical studies, such as plasma-surface interactions. A preliminary plasma treatment of the polymer substrate before film gr owth is found to increase the sticking of the first monolayers of the film, and therefore its adhesion, as shown by conventional thermal adh esion tests. The treatment consists of three successive steps: argon p lasma, (NH3, Ar) plasma and (SiH4, He, Ar) plasma. The first two steps induce a densification of the bulk and an activation of the surface ( formation of C-N bonds), while the silane plasma leads to the growth o f a very thin silicon oxide layer. In particular, the increase in the film adhesion appears to be closely related to the presence of a Si-O vibrational mode located at 1030 cm-(1).