XPS investigation of the chemical characteristics of Kapton films ablated by a pulsed TEA CO2 laser

Laser ablation of 125-μm-thick Kapton polyimide films was carried out in air using a pulsed TEA CO2 laser at 9.3 μm. Laser-produced fibers protruding from the ablated surface results in a bad surface quality. Changes in the composition and the chemical characteristics of the ablated surfaces were identified by X-ray photoelectron spectroscopy (XPS). The C/O and C/N atomic ratios as well as the peak area of the C 1s spectra at 284.7 eV in the ablated area increase, while the peak areas of the C 1s spectra corresponding to the carbonyl groups (CO) in the imide system and the ether groups (CO) decrease. These suggest that the fiber bundles consist mainly of carbon. Moreover, the amide groups, nitrile groups (CN) and the benzene derivatives were detected after laser irradiation due to the breakage of the CN bonds in the imide ring and ether groups. Upon increasing the fluence to 10.6 J/cm2, the shake up at 537.6 eV decreases further, yet the amide groups as well as the shake up at 291 eV almost disappeared. This is because benzene derivatives decompose completely and the carbonyl groups are eliminated from the aromatic systems due to a large temperature rise. Therefore, the increase in fluence may improve the thermal decomposition during the TEA CO2 laser ablation of the Kapton films.