Strongly coupled, high-quality plasmonic dimer antennas fabricated using a sketch-and-peel technique

• Main Authors: Gittinger Moritz, Höflich Katja, Smirnov Vladimir, Kollmann Heiko, Lienau Christoph, Silies Martin
• Format: Article
• Language: English
• Published: De Gruyter 2020-02-01
• Series: Nanophotonics
• Subjects: helium-ion beam lithography; sketch and peel; plasmonic nanostructures; single-particle dark-field spectroscopy; strong coupling; quality factor; near-field enhancement
• Online Access: http://www.degruyter.com/view/j/nanoph.2020.9.issue-2/nanoph-2019-0379/nanoph-2019-0379.xml?format=INT

A combination of helium- and gallium-ion beam milling together with a fast and reliable sketch-and-peel technique is used to fabricate gold nanorod dimer antennas with an excellent quality factor and with gap distances of less than 6 nm. The high fabrication quality of the sketch-and-peel technique compared to a conventional ion beam milling technique is proven by polarisation-resolved linear dark-field spectromicroscopy of isolated dimer antennas. We demonstrate a strong coupling of the two antenna arms for both fabrication techniques, with a quality factor of more than 14, close to the theoretical limit, for the sketch-and-peel–produced antennas compared to only 6 for the conventional fabrication process. The obtained results on the strong coupling of the plasmonic dimer antennas are supported by finite-difference time-domain simulations of the light-dimer antenna interaction. The presented fabrication technique enables the rapid fabrication of large-scale plasmonic or dielectric nanostructures arrays and metasurfaces with single-digit nanometer scale milling accuracy.