Surface-enhanced infrared absorption:: Infrared ellipsometry of au evaporated ultrathin organic films

A detailed analysis of the enhancement and band shapes of vibrational bands after evaporation of 4 nm of gold on the organic film was studied. The surface enhanced infrared absorption (SEIRA) effect was observed for organic films containing the nitro group. Gold island films were prepared by evaporation of gold from a Knudsen cell. The nominal thickness was determined by quartz micro balance measurements. The nitrobenzene films (NB) were prepared electrochemically on H-passivated Si(111) substrates. A photometric ellipsometer attached to a Bruker IFS 55v/S Fourier Transform Interferometer was used for the IR ellipsometric experiments. The optical simulation of the film isotropic organic film without gold islands was performed within an optical layer model using a film with a thickness of 3 nm and a high frequency refractive index. Characteristic bands of the NB film were observed in all IR ellipsometric spectra.