Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 75: Plasmonics and Nanooptics
O 75.8: Poster
Wednesday, March 18, 2015, 18:15–21:00, Poster A
Enhanced near-field coupling of plasmonic antennas with few-nm gap sizes fabricated by helium ion beam milling — Heiko Kollmann1, Xianji Piao2, Martin Esmann1, Simon F. Becker1, Dongchao Hou1, Henning Vieker3, André Beyer3, Armin Gölzhäuser3, Namkyoo Park2, •Martin Silies1, and Christoph Lienau1 — 1Carl von Ossietzky-Universität Oldenburg — 2Seoul National University, Korea — 3Universität Bielefeld
Metallic nanoantennas are able to localize far-field electromagnetic waves on sub-wavelength scales. Standard fabrication tools such as Electron Beam Lithography and Ga-based Focused Ion Beam (FIB) milling lead to sub-20-nm feature sizes. In the recent past, He-ion based lithography (HIL) has proven to push this limit below 10 nm [1,2]. Here, we combine Ga-based FIB and HIL for the fabrication of gold antennas with variable gap sizes down to a few nanometers. Using polarization-sensitive linear and nonlinear third harmonic (TH) spectroscopy, the linear optical resonances of single gold antennas and the TH emission intensities are analyzed for different feed gap distances. Both the spectral red-shift of the linear emission and the increased TH signal for small feed gaps are taken as a signature for the improved coupling of the antennas. Our experimental findings are strongly supported by FEM calculations and demonstrate that He-ion beam lithography is a highly attractive and promising new tool for the fabrication of plasmonic nanoantennas with few-nanometer feature sizes.
[1] M. Melli et al., Nano Letters 13, 2687-2691 (2013) [2] H. Kollmann et al., Nano Letters 14, 4478-4784 (2014)