Raman Scattering Analysis of Thin Film Coatings Using Guided Waves

Abstract

Selected refractory oxide, thin film coatings have been analyzed using Raman spectroscopy. Diamond and rutile prisms were used to couple the probe beam into the thin film coatings which served as waveguides. Propagation of the probe beam as a guided wave in the thin film increases the probability for Raman scattering by species in the thin film, compared to techniques which depend on a single pass through or probe beam reflection at the film. Because the probe beam is confined entirely within the thin film coating, Raman spectra are obtained which are generally free of vibrational bands due to the substrate. The combination of more efficient coupling between the probe beam and the thin film and the elimination of substrate interferences results in improved sensitivity and the ability to record recognizable Raman spectra of thin films composed even of materials that are relatively inefficient Raman scatterers.