Gold coatings on polyethyleneterephthalate nano-patterned by F2 laser irradiation

In this work we present periodic surface structures generated by linearly polarized F₂ laser light (157 nm) on polyethyleneterephthalate (PET). Atomic force microscopy was used to study the topological changes induced by the laser irradiation. The laser irradiation induces the formation of periodic ripple structures with a width of ca 130 nm and a height of about 15 nm in the fluence range 3.80-4.70 mJ/cm² and the roughness of the polymer surface increases due to the presence of these periodic structures. Subsequently, the laser modified PET foils were coated with a 50 nm thick gold layer by sputtering. After Au deposition on the PET foils with ripple structure, the roughness of surface decreases in comparison to PET with ripples without Au coating. For 50 nm thick Au layers, the ripple structure is not directly transferred to the gold coating, but it has an obvious effect on the grain size of the coating. With considerably thinner Au layers, the ripple structures are smoothened but preserved.