Berlin 2024 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 21: Optical Analysis of Thin Films
DS 21.6: Vortrag
Freitag, 22. März 2024, 11:15–11:30, A 053
Surface-Sensitive and Bulk-Suppressed Raman Scattering by Transferable Nanoporous Plasmonic Membranes — •Pietro Marabotti1, Roman M. Wyss1, Günter Kewes1, Martin Frimmer2, Karl-Philipp Schlichting2, Markus Parzefall2, Eric Bonvin2, Martin F. Sarott2, Morgan Trassin2, Lala Habibova1, Giorgia Marcelli1, Marcela Giraldo2, Jan Vermant2, Lukas Novotny2, Mads C. Weber3, and Sebastian Heeg1 — 1Humboldt-Universität zu Berlin, Germany — 2ETH Zürich, Switzerland — 3Le Mans Université, France
The Raman response of surfaces or thin films is often too weak to be detected and obscured by dominant bulk signals. Here we overcome this limitation by placing a transferable porous Au membrane (PAuM) on top of the surface of interest. Slot-like nanopores in the membrane act as plasmonic slot antennas and enhance the Raman response of the surface underneath. The PAuM also suppresses the penetration of the excitation laser into the bulk, efficiently blocking the bulk Raman signal. Using graphene as a model surface, we show that these two effects increase the surface-to-bulk Raman signal ratio by 3 orders of magnitude. We find that 90% of the Raman enhancement occurs within the top 2.5 nm of the material, demonstrating truly surface-sensitive Raman scattering. To validate our approach, we analyze the surface of a LaNiO3 thin film, observing a Raman mode splitting from the surface-layer, which is evidence that the surface structure differs from bulk. This shows that PAuM give direct access to Raman signals of surfaces and their structural properties.
Keywords: Raman spectroscopy; Surface; Surface-sensitive Raman scattering; Plasmonic nanopore; Complex oxide thin film