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O: Fachverband Oberflächenphysik

O 59: Plasmonics and Nanooptics

O 59.8: Poster

Dienstag, 21. März 2017, 18:30–20:30, P2-OG1

Raman enhancement due to gold nanoparticles on a graphene monolayer — •Marcel Weinhold, Sangam Chatterjee, and Peter J. Klar — Justus Liebig University Giessen, Institute of Experimental Physics I, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany

Tip-enhanced Raman spectroscopy (TERS) is a powerful technique for analyzing molecular vibrations as well as lattice dynamics in bulk materials with a high spatial resolution down to a few nanometers, and combines the advantages of ordinary Raman spectroscopy and atomic force microscopy.
Despite the huge progress in improving the achievable spatial resolution of tip-enhanced Raman spectroscopic techniques, there remain many questions unanswered regarding the mechanisms, that lead to the enhancement of Raman signals. The understanding of these effects is essential for improving the TERS techniques. We study the enhancement effects of gold nanoparticles (representing a TERS tip) deposited on a graphene monolayer. Graphene was employed because of its two-dimensionality, its strong Raman signals, and the opportunity of purchasing samples with coverages close to 100%. We used Raman mapping with different excitation lasers, and various laser powers to determine the influence on the Raman enhancement. The enhancement factor shows a dependence on the excitation wavelength and varies for the different graphene modes. Additionally, we obtain a systematic shift in the measured phonon-frequencies probably related to a plasmonic coupling between gold and graphene that correlates with the applied laser power.