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Title: Split-wedge antennas with sub-5 nm gaps for plasmonic nanofocusing

Here, we present a novel plasmonic antenna structure, a split-wedge antenna, created by splitting an ultrasharp metallic wedge with a nanogap perpendicular to its apex. The nanogap can tightly confine gap plasmons and boost the local optical field intensity in and around these opposing metallic wedge tips. This three-dimensional split-wedge antenna integrates the key features of nanogaps and sharp tips, i.e., tight field confinement and three-dimensional nanofocusing, respectively, into a single platform. We fabricate split-wedge antennas with gaps that are as small as 1 nm in width at the wafer scale by combining silicon V-grooves with template stripping and atomic layer lithography. Computer simulations show that the field enhancement and confinement are stronger at the tip–gap interface compared to what standalone tips or nanogaps produce, with electric field amplitude enhancement factors exceeding 50 when near-infrared light is focused on the tip–gap geometry. The resulting nanometric hotspot volume is on the order of λ 3/10 6. Experimentally, Raman enhancement factors exceeding 10 7 are observed from a 2 nm gap split-wedge antenna, demonstrating its potential for sensing and spectroscopy applications.
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ; ORCiD logo [1]
  1. Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Electrical and Computer Engineering
  2. Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Electrical and Computer Engineering; Bethel Univ. Saint Paul, MN (United States). Physics Dept.
  3. Univ. of Colorado, Boulder, CO (United States)
  4. ETH Zurich, Zurich (Switzerland). Optical Materials Engineering Lab.
Publication Date:
Grant/Contract Number:
FG02-06ER46348; 339905
Published Article
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 16; Journal Issue: 12; Journal ID: ISSN 1530-6984
American Chemical Society
Research Org:
Univ. of Colorado, Boulder, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
77 NANOSCIENCE AND NANOTECHNOLOGY; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; atomic layer deposition; atomic layer lithography; gap plasmon; optical antenna; surface-enhanced Raman scattering (SERS); template stripping
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1337514