Laser ablation of aryltriazene photopolymer films: Effects of polymer structure on ablation properties

Laser ablation of a homologous series of four tailor-made UV-sensitive aryltriazene polymers with an increasing content of photodecomposible chromophore units has been studied with a XeCl excimer laser (emission wavelength 308 nm). Irradiation induces a photolytic cleavage of the aryltriazene chromophores which then leads to a fragmentation of the polymer main chain. Resulting effects of different chromophore densities on the ablation parameters of thin films were investigated by profilometry analysis of the ablated spots. No relevant influence of the chromophore density was found for the threshold fluence of laser ablation (∼25 mJ/cm2) of the four polymers for single-pulse experiments. In the same way, ablation depths per pulse at a given laser fluence and with the same film thickness showed no significant differences. Remarkable differences were found for the resulting surface morphology of ablated spots at laser fluences near the ablation threshold. Homogeneous ablation resulting in a flat and smooth bottom surface of the ablated pits were observed mainly for laser fluences above the range of two times the ablation threshold (>∼50 mJ/cm2). Investigating the ablation behaviour of such triazene-based photopolymers allows to derive photophysical key parameters necessary for the optimization of application processes where the designed polymers are used as sacrificial absorbing release layers in advanced laser-induced forward transfer (LIFT) applications.