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

Abstract

Abstract 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.