Gold coating of poly(ethylene terephthalate) modified by argon plasma

Little information has been published concerning the interaction of gold with polymers. In the context of this lack of information, we decided to investigate the effect of Ar plasma treatment on the surface properties of poly(ethylene terephthalate) (PET) in order to examine its possible application for metal-polymer adhesion improvement. The plasma treatment leads to an immediate increase of the PET's surface wettability, which however significantly depends on the sample aging, more specifically on the time elapsed after the treatment. X-ray photoelectron spectroscopy (XPS) measurements revealed that the oxygen concentration in the surface-near layers increases as a result of the treatment, but that it also changes with time for the samples in contact with the atmosphere, probably as a result of polar group rearrangements. Plasma initiated ablation and Au sputtering increases the surface roughness. The nanoindenter measurements revealed that the treatment increases the microhardness of treated PET. Contrary to hardness, the elastic modulus decreases. Scratch tests showed that the deformation of samples consisting of Au coatings deposited on both pristine and treated PET was elastic rather than plastic. We conclude from the nanoindenter data that the plasma modification does not affect the adhesion of gold on PET, but the X-ray diffractometry (XRD) analysis showed that the Au film deposited on the as-treated PET, and on PET aged for 14 d are the most stable.