Absorption of acrylates and polysilazanes in the far UVC and the VUV regions

A simple but reliable method was developed for the determination of wavelength-dependent absorption coefficients in the vacuum-UV (VUV) spectral range 160 nm < λ < 195 nm. Absorption coefficients were determined on thin layers of UV curable compounds like acrylates and of polysilazanes, which are subject to photo-induced conversion into SiOx layers. Results were discussed in terms of changing values of the absorption coefficients during irradiation. In case of acrylates polymerization leads to the decrease of the absorption coefficients especially in the wavelength range about 195 nm from about 10 μm−1 to about 1 μm−1. Results of quantum-chemical calculations explain this finding by the depletion of double bonds for which ππ* transitions are characteristic. XPS depth profiles reveal the VUV induced degradation of carboxyl and ether functionalities in a thin surface layer corresponding to the penetration depth of the VUV photons.