title: Gradual photochemical-induced conversion of liquid polydimethylsiloxane layers to carbon containing silica coatings by VUV irradiation at 172 nm.
abstract: Thin liquid layers of polydimethylsiloxane (PDMS) were irradiated by VUV light under nitrogen atmosphere using a Xe(2)- excimer lamp. The irradiated layers were analyzed with infrared reflection absorption spectroscopy (IRRAS) and X-ray photoelectron spectroscopy (XPS), showing a gradual photochemical-induced conversion of the liquid PDMS to solid SiO(2)-like coatings. IRRAS measurements revealed a smooth frequency shift of the maximal absorption band from 1111 to 1231 cm(-1) with increasing irradiation energy density caused by a gradual shift from the asymmetric Si-O stretching vibration of PDMS to the longitudinal optical (LO) mode of SiO(2). The shift was found to be dependent on the applied irradiation energy density and the O/Si ratio in the film analyzed by XPS measurements. The atomic ratio of O/Si increases from 1:1 to about 2.5:1. At the same time, the atomic ratio of C/Si decreases from 2:1 down to 1:6.5. Images taken by high resolution field emission scanning electron microscopy (FESEM) and scanning force microscopy (SFM) show a smooth surface without cracks or pores. The controllable coating properties in combination with the possibility for local irradiation using masks are promising high potential for the coating technology.
authors.affiliation: Fraunhofer Institute for Manufacturing Technology and Applied Materials Research, Wiener Strasse 12, D-28359 Bremen, Germany. doe@fraunhofer.ifam.de
authors.forename: Christopher
authors.initials: C
authors.lastname: Dölle
authors.forename: Marcus
authors.initials: M
authors.lastname: Papmeyer
authors.forename: Matthias
authors.initials: M
authors.lastname: Ott
authors.forename: Klaus
authors.initials: K
authors.lastname: Vissing