Berlin 2015 – scientific programme

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DS: Fachverband Dünne Schichten

DS 26: Layer Properties: Electrical, Optical, and Mechanical Properties

DS 26.7: Talk

Wednesday, March 18, 2015, 16:30–16:45, H 2032

Tip-enhanced Raman spectroscopy (TERS) on La₂CoMnO₆ thin films: Field enhancement and polarisation effects — •Christoph Meyer, Sebastian Merten, Sebastian Hühn, Markus Jungbauer, Vasily Moshnyaga, Bernd Damaschke, and Konrad Samwer — I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen

B-site ordered La₂CoMnO₆ (LCMO) with monoclinic P12₁/n₁ structure can be derived from a perovskite ABO₃ by alternating layers of Co²⁺ and Mn⁴⁺ on the B-site. It is a promising material for spintronic applications due to ferromagnetic ordering, magnetodielectric coupling and multiferroic behavior. Since the performance of LCMO is strongly affected by the degree of B-site ordering, we applied Raman spectroscopy to correlate phonon spectra with the ordering. A study of the far-field Raman and tip-enhanced Raman spectroscopy (TERS) of LCMO thin films on SrTiO₃(100) and SrTiO₃(111) substrates, grown by metalorganic aerosol deposition (MAD), was performed. Polarization dependent TERS was carried out to determine the contributions for enhancement due to surface plasmon polariton (SPP) excitation and depolarization. Due to B-site cation ordering, the spectra exhibit a strong A_g mode at 645 cm⁻¹, generated by octahedral (Co/Mn)O₆ stretching vibrations with largest TERS contrast of ∼60−100 in the crossed polarization configuration. A tip-induced depolarization effect and a significant enhancement due to general field amplification were observed. Financial support by the DFG via project SFB 1073/B04 is gratefully acknowledged.