Irradiation wavelength selective surface modification of a triazeno polymer

Standard spectroscopic and surface analysis techniques were used to study a triazeno polymer after laser treatment. Two different excimer lasers, KrF at 248 nm and XeCl at 308 nm, were applied as irradiation sources. For both excimer lasers fluences below and above the threshold of ablation were used. In the case of fluences below the threshold of ablation the irradiation led to a decrease of the absorption of the triazeno chromophore. From XPS spectrum and contact angle measurements a surface oxidation of the polymer is identified. After irradiation with fluences above the threshold of ablation for both irradiation wavelengths a different behavior is observed. Irradiation with the XeCl laser led to a less pronounced surface roughening as compared to KrF laser treatment. With the XPS and contact angle measurements, only slight changes could be detected. A totally different behavior was found for irradiation with the KrF excimer laser. The surface of the polymer turned black after the irradiation, and the oxygen and nitrogen content is drastically reduced, as determined from the XPS spectrum. The SEM pictures revealed the appearance of microstructures of about 5 mu m size with some ''treelike'' structures at the top of the ''naps''. Contact angle measurements show also the existence of a nonpolar surface. Spectroscopic techniques showed that there exists a clear difference between the irradiation of the triazeno polymer at the two wavelengths under ablation conditions. Excitation of the triazeno chromophore at 308 nm leads to clear ablation, whereas the irradiation with 248 nm introduces microstructures and a carbonized surface.