Chemical modifications in femtosecond ultraviolet (248 nm) excimer laser radiation-processed polyimide

Using X-ray photoelectron spectroscopy (XPS), we have investigated the surface of polyimide (kapton), which was subjected to processing by femtosecond UV radiation from an excimer laser (KrF: λ=248 nm , t p∼380 fs) in air. Significant variations were observed in the C 1s and O 1s spectra of the processed surface of kapton, indicating chemical modifications due to loss of volatile groups such as CO and CN. Incorporation of oxygen via bonding as COC of the aromatic rings was observed during processing. Bulk characterization of the processed kapton by Fourier transform infrared spectroscopy (FTIR) allowed a study of laser-induced modifications in the material at energy densities below the ablation threshold. Scanning electron microscopy (SEM) studies of the surface morphology of the processed zone of kapton indicates mechanically clean and damage-free processing with good edge quality.