Chemical surface modification of poly (ethylene terephthalate) by excimer irradiation of high and low intensities

Poly (ethylene terephthalate) (PET) was modified by a KrF 248 nm excimer la ser with high- (above ablation threshold) and low- (below ablation threshol d) fluence. The PET surface develops usually a periodic roughness or ripple s with high fluence. The roughness size is in the micron range and the surf ace shows signs of global melting. However, the ripple size can be reduced to sub-micron level by an irradiation of the sample below the ablation thre shold with a polarized beam. The morphology of the irradiated surfaces was examined by scanning electron microscopy (SEM). Chemical surface changes of the materials were characterized by X-ray photoelectron spectroscopy (XPS) . The PET modification by high fluence will normally results in the deposit ion of some yellow to black materials (debris), on the treated surface. The debris are ionized and from carbon rich materials which finally condense f orming higher aggregates, resulting in a reduction of O/C ratio. By contras t, modification of PET surfaces by low fluence leads to an oxidation and al most no ablation is detected. The increase of oxygen concentration on low f luence modified surfaces is probably due to a subsequent reaction with atmo spheric O-2 during irradiation. Our work suggests that a careful selection of laser parameters for the surface modification of polymer is of primary i mportance.