Spectroscopic ellipsometry study of plasma-polymerised vinyltriethoxysilane films

Plasma-polymerised vinyltriethoxysilane (pp-VTES) films with thicknesses ranging from 20 nm to about 5 μm were studied by combined method of spectroscopic ellipsometry and optical reflectivity in VIS and UV spectral zone. For these photon energies Tauc-Lorentz dielectric function (with a band gap of about 2.5 eV) was found to be an appropriate parameterisation of pp-VTES optical constants. Various sample models, accounting for the presence of film interfaces, film refractive index gradient profile and film thickness non uniformity were considered. Pp-VTES films (t < 1 μm) can be considered as homogeneous films, whereas thick films show imperfections, which dominant character was assigned to film thickness non uniformity.