UV-irradiation induced modification of PDMS films investigated by XPS and spectroscopic ellipsometry

UV-irradiation (172 nm) induced changes of PDMS surfaces were investigated with X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry (SE). Both methods indicate the modification of the PDMS to a silica-like surface (SiO2). These conclusions could be drawn from the elemental composition determined by XPS and the binding energy shifts in the XPS spectra of the Si 2p and O 1s levels. Similarly the refractive index n determined with ellipsometry reaches a value close to the one of SiO2. Additionally, ellipsometry allows to monitor the decrease of the original film thickness with increasing UV-irradiation time.