Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 51: Poster: Electronic Structure of Surfaces: Spectroscopy, Surface States

O 51.3: Poster

Dienstag, 13. März 2018, 18:15–20:30, Poster B

Electron-Rich surface of thin La_0.7Sr_0.3MnO₃ films revealed by Surface-Enhanced Raman Spectroscopy — •Sebastian Merten, Vitaly Bruchmann-Bamberg, Bernd Damaschke, Konrad Samwer, and Vasily Moshnyaga — I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Perovskite manganites are appealing materials for various potential applications in spintronics, catalysis or fuel cells. For all of them the electronic and atomic structure of the surface/interface is crucial for the performance of the future device. Unfortunately, the understanding of the manganite surface is still in its infancy. Surface-Enhanced Raman (SER) Spectroscopy represents a versatile tool to simultaneously probe different degrees of freedom and the small penetration depth of the surface plasmon (< 5nm) limits the probing area to the surface layers. Here, we present a detail SER study of thin La_0.7Sr_0.3MnO₃ (LSMO) films grown on different substrates. SER spectra reveal a Jahn-Teller (JT) dominated surface structure, in contrast to the "bulk" Raman spectra where the JT modes are suppressed due to the rhombohedral structure of LSMO. Our experiments confirm theoretical calculations, which show a charge-transfer from the bulk to the surface and thus, formation of Mn³⁺-ions at the surface. Furthermore, an enhancement of a specific JT mode depending on the epitaxial strain was observed. Temperature-dependent measurements reveal a second transition temperature at around T = 260 K. Financial support from DFG via SFB 1073 (TP B01, B04 and A02) is acknowledged.