Infrared Spectroscopy of LiF on Ag and Si

We present the results of infrared optical studies of thin lithium fluoride films evaporated on silver and silicon substrates. Polarized oblique-incidence reflectance and multiple-angle-of incidence FTIR ellipsometry has been used to study the spectral range of longitudinal optic (LO) lattice vibrations. We discuss in detail the lineshapes, and use the pronounced difference of the optical response of metallic and insulating substrates to elucidate their origin. In particular, we model the field distribution in the stratified structures, and specify the spatial distribution of the absorbed energy.