Figure 6. Spectral analyses of photoactivated polymer surface.

(a) The carbon 1s XPS spectra are shown by black dotted curves for the spin-coated Cytop films before (upper part of panel) and after (lower part of panel) the VUV irradiation. It is clearly observed that the irradiation affords a decrease in the peak at 290.5 eV and an increase in the peak at 286.3 eV. The observed spectra were well fitted by the sum (red solid curve) of four Gaussian lines (gray solid curves for each). Among them, the largest peak at 290.5 eV can be assigned as difluoride carbons, while the peak at 286.3 eV can be assigned as the carbons in structures resulting from defluorination of the polymer. (b) First-derivative ESR spectra of a free-standing Cytop film just after the VUV irradiation with a dose of 512 mJ cm⁻² (solid curve) and 25 days after the VUV irradiation (dashed curve). The irradiation affords appearance of the ESR signal due to peroxy radicals that are most probably formed by the reaction of carbon radicals with oxygen. ESR absorption spectra obtained by integrating the first-derivative signal are shown at the bottom. The upper panel is the spectrum of the film just after the VUV irradiation, while the lower panel is the spectrum of the film 25 days after the VUV irradiation. These spectra are well fitted by the sum (red solid curve) of three resonance components, respectively; the former with g-values at 2.0252 (green curve), 2.0113 (blue curve) and 2.0062 (grey curve), and the latter with g-values at 2.0249 (green curve), 2.0114 (blue curve) and 2.0071 (grey curve).