The use of SiO2-like layers as adhesion-promoting inter-layers between a reactive plasma polymer film and a gold substrate is compared to a self-assembled monolayer of dodecanethiol and to bare gold. The chemical structure of the silicon oxide film is optimized by varying feed gas ratios and process input power. A 5 s oxygen plasma modification of the SiO2-like film deposited. from hexamethyldisiloxane has been found to be vital to prepare the surface for covalent bonding of the subsequently deposited reactive polymer layer. Film chemical structures and reactivity have been studied using IR reflection-absorption spectroscopy, XPS, contact angle goniometry and SPR spectroscopy.