Formation of the surface structure of polyethylene-terephtalate (PET) due to ArF excimer laser ablation

The development process of the surface structure on polyethylene-terephtalate (PET) has been investigated. It was found that the average dimension and shape of its unit cells depend on the excimer laser fluence, the incident angle of the ablating laser beam (the longitudinal dimension is proportional to cons X tan(alpha)+D formula, where D means the average dimension of the unit cell at alpha = 0 degrees) and the number of shots (the average dimension and height proportional to the logarithm of the number of shots). A dye laser based arrangement was constructed to investigate the temporal dependence of the scattered probe light intensity from the ablated polymer surface. It was found that the formation of the surface structure takes place in the time range of 5-10 mu s. We used a heat diffusion melting model to explain the development of the surface structure. A simple 1D simulation of the heat transfer shows that the lifetime of the liquid phase (similar to 1-7 mu s) is comparable with the time scale mentioned above.