Characterization of the layer growth of plasma-polymerized HMDSO coatings on polycarbonate

Plasma-polymerized silicon organic coatings have a cauliflower-like structu re with embedded agglomerates. Oxygen as an additional reactive gas leads t o more glass-like coatings with a smoother surface. Also the structure of t he substrate affects the structure of the plasma-polymerized coating. Thus defects on the substrate cause volume polymerization as well as an increase d agglomerate growth. These agglomerates have an oxygen-enriched and silico n-reduced chemical composition compared to the surrounding matrix. Moreover these agglomerates are also softer than the matrix. This results in a chan ged behavior towards stress. If there is a crack nucleation within the laye r, the cracks will run mainly around the agglomerates. The cracks do also f ollow a line up of agglomerates, which is caused by a bulge or a scratch on the substrate surface. A large number of agglomerates does not only cause a haze of the coating by changed light scattering, but also by the formatio n of cracks water can get between the substrate and the coating and thus ha ve a negative influence on layer adhesion. I Consequently a large number of agglomerates has to be avoided. The tests have shown that structures like those on a written, but not sputtered CD are flattened with a HMDSO coating after 80 s. The edges of the pits do not lead to a changed layer growth. [GRAPHICS]