We have studied lattice dynamic properties of SrTiO 3 thin films from 5 to 300 K using metaloxide 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 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. [S0031-9007(99)09277-7]

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We have used a metal-oxide bilayer Raman scattering technique to study lattice dynamics in SrTiO 3 thin films. The SrTiO 3 thin films were epitaxially grown on a conducting metal-oxide layer which reflects the exciting laser beam so that it does not enter the LaAlO 3 substrate. Raman scattering from the SrTiO 3 thin films was clearly observed, including the first-order Raman peaks forbidden by the cubic symmetry in single crystals. We suggest that strain exists in the films, which changes the crystal symmetry and will affect the dielectric properties of the SrTiO 3 thin films.

In si tu Raman scattering, ultraviolet-photoemission-spectroscopy (UPS), and electron-energy-lossspectroscopy (EELS) measurements have been performed on crystalline films of RbC6O through the fcc-toorthorhombic structural phase transition. The Raman spectra exhibit large changes in intensity of modes not active for isolated icosahedra, including ungerade vibrations. This is attributed to a substantial increase in interfullerene coupling in the presence of C60 merohedral disorder. UPS measurements indicate a finite density of states at the Fermi energy for both phases with small changes in the C60 derived states through the transition. Low-energy metalliclike excitations are observed in EELS.