Dresden 2017 – scientific programme

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DS: Fachverband Dünne Schichten

DS 36: Postersession I

DS 36.25: Poster

Wednesday, March 22, 2017, 17:00–19:00, P2-EG

Surface-enhanced Raman spectroscopy (SERS) on La_0.7Ca_0.3MnO₃: Indication for a Jahn-Teller dominated surface structure — •Sebastian Merten, Bernd Damschke, Konrad Samwer, and Vasily Moshnyaga — I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany

Raman spectroscopy is a powerful tool to study different degrees of freedom at the same time. However, for thin films its use is limited by the normally strong background of the substrate. SERS allows one to overcome this limitation and opens new insights into the structural properties of ultrathin films and surfaces due to the small penetration depths of less than 5 nm. Here we report SERS measurements on thin TiO₂ and La_0.7Ca_0.7MnO₃ films grown by metalorganic aerosol deposition (MAD). As model system we used 20nm thick TiO₂ on a Si(100) substrate and a gold nano-layer on top of it, both grown by MAD. Only Si background is seen in the Raman spectrum of bare TiO₂. After deposition of the Au-layer, a strongly enhanced E_g-mode at 143 cm⁻¹ of the anatase TiO₂ phase was observed. LCMO/MgO(100) and LCMO/LaAlO₃(001) films show a strong enhancement of the Jahn-Teller modes compared with normal Raman spectroscopy. This suggests the presence of cooperative Jahn-Teller effect at the film surface due to symmetry-breaking-induced electron-lattice reconstruction. Financial support from DFG via SFB 1073 (TP B01 and B04) is acknowledged.