Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 29: Near-Field Microscopy
O 29.4: Talk
Tuesday, March 17, 2015, 14:45–15:00, MA 042
Gap mode formation in metallic, nanofocusing SNOM tapers — •Simon F. Becker1, Martin Esmann1, Kyungwan Yoo1,3, Petra Groß1,2, Ralf Vogelgesang1, Namkyoo Park3, and Christoph Lienau1 — 1Carl von Ossietzky Universität, 26111 Oldenburg, Germany — 2Universität Osnabrück, 49076 Osnabrück, Germany — 3Seoul National University, Seoul, Korea
Surface plasmon polaritons (SPPs) propagating on metallic tapers get nanofocused at the apex. This largely reduces unwanted background contributions in apertureless scanning near-field optical microscopy (SNOM) [1,2] and provides direct access to broadband nanospectroscopy.
Here, we analyze the near-field formation at the apex of single crystalline gold tapers by using them as SNOM probes [3]. We investigate the imaging mechanism in scattering geometry and in the Fourier domain. The experimental results are compared to detailed finite element method (FEM) simulations. In particular, we find strong evidence for the formation of a gap mode between probe and sample, both in the experiment and the simulation. The results indicate that this spectrally broadband interaction is extremely short-ranged and has the potential to enhance the spectroscopic imaging resolution down to the single nanometer regime.
[1] M.I. Stockman, PRL 93, 137404 (2004); [2] S. Schmidt et al., ACS Nano 6, 6040 (2012); [3] M. Esmann et al., BJ Nano 4, 603 (2013).