ABSTRACT
Graded films have higher adhesion strengths because very firm organic-toorganic bonding at the interface between the substrate and initial plasma coating layer exists, and a gradual change of composition and structure over the thickness of film is obtained. If the single-graded process is used, copper or silver can be deposited at the very beginning of the film deposition due to the high sputter yield of copper or silver, and this may inhibit organic-to-organic bonding. This becomes clearer if adhesion values of the film at different argon-to-methane ratios are compared. A low methane-to-argon ratio gives high sputtering of copper or silver, thus decreasing the adhesive strength. The copper or silver content in the initial plasma polymer layer, as indicated in Tables 21.3 and 21.4, respectively, shows the expected trend.
