Examination of the influence of molecular weight on polymer laser ablation: polystyrene at 248 nm

Following previous studies on the influence of the polymer molecular weight (M-W) on the ablation of poly(methyl methacrylate) (PMMA) at 248 nm, this work extends the examination to the ablation of polystyrene (PS) at 248 nm. The ablation threshold and the etching rates are found to be nearly independent of M-W. Optical microscopy demonstrates an excellent crater morphology, few small bubbles are formed on the surface of the low M-W. Examination of the formation kinetics of products in the irradiation of samples doped with the photoreactive iodophenanthrene demonstrates that high temperatures develop upon irradiation, suggesting that thermal mechanism dominates in the ablation of PS at 248 nm. In similarity to the etching rates, the attained temperatures are largely independent of the PS M-W. The factors for the weak dependence of the process on PS M-W are discussed.