Observation of the First-Order Raman Scattering inSrTiO3Thin Films

Abstract

We have studied lattice dynamic properties of ${\mathrm{SrTiO}}_3$ thin films from 5 to 300 K using metal-oxide bilayer Raman scattering. First-order zone-center optical phonons, symmetry forbidden in single crystals, have been observed in the thin films, indicating strain-induced lowering of symmetry. The asymmetric line shape of the ${\mathrm{TO}}_2$ phonon is interpreted as evidence for micropolar regions in the thin films, likely due to oxygen vacancies. The optical phonon lines and the asymmetry persist up to room temperature.