Resonant Optical Antennas with Atomic-Sized Tips and Tunable Gaps Achieved by Mechanical Actuation and Electrical Control Academic Article uri icon

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abstract

  • Enhanced electromagnetic fields in nanometer gaps of plasmonic structures increase the optical interaction with matter, including Raman scattering and optical absorption. Quantum electron tunneling across sub-1 nm gaps, however, lowers these effects again. Understanding these phenomena requires controlled variation of gap sizes. Mechanically actuated plasmonic antennas enable repeatable tuning of gap sizes from the weak-coupling over the quantum-electron-tunneling to the direct-electrical-contact regime. Gap sizes are controlled electrically via leads that only weakly disturb plasmonic modes. Conductance signals show a near-continuous transition from electron tunneling to metallic contact. As the antenna's absorption cross-section is reduced, thermal expansion effects are negligible, in contrast to conventional break-junctions. Optical scattering spectra reveal first continuous red shifts for decreasing gap sizes and then blue shifts below gaps of 0.3 nm. The approach provides pathways to study opto- and electromolecular processes at the limit of plasmonic sensing.

authors

  • Gruber, Cynthia M
  • Herrmann, Lars
  • Bellido, Edson P
  • Dössegger, Janine
  • Olziersky, Antonis
  • Drechsler, Ute
  • Puebla-Hellmann, Gabriel
  • Botton, Gianluigi
  • Novotny, Lukas
  • Lörtscher, Emanuel

publication date

  • June 10, 2020