RF sputtered amorphous chalcogenide thin films for surface enhanced infrared absorption spectroscopy

In this work, the fabrication of amorphous chalcogenide thin films (As2S3 and Ge25Sb10Se65) by radio-frequency sputtering was studied. The morphology, chemical composition, optical properties and structure of fabricated layers as well as bonding arrangement at the surface of the films were investigated by scanning electron microscope with an energy-dispersive X ray analyzer, atomic force microscopy, transmittance measurements, variable angle spectroscopic ellipsometry, prism coupling technique, X-ray reflectometry, profilometry, conductivity measurements, Raman scattering spectroscopy and X-ray photoelectron spectroscopy. As2S3 thin films show some crystals formation on the surface indicating the ageing (oxidation) of the films. Ge25Sb10Se65 layers are more stable against oxidation and the morphology of the layers seems to be influenced by the sputtering pressure. Moreover, gold nanoparticles were deposited onto Ge25Sb10Se65 thin films by direct-current sputtering to assess surface enhanced infrared absorption spectroscopy of prepared structures. The morphology and thickness of gold films were also investigated. The infrared transmission spectra of a self-assembled monolayer of 4-nitrothiophenol deposited on gold are enhanced according to surface selection rules