Split-Wedge Antennas with Sub-5 nm Gaps for Plasmonic Nanofocusing
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Date
2016-12-14
Publication Type
Journal Article
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Abstract
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 λ3/106. Experimentally, Raman enhancement factors exceeding 107 are observed from a 2 nm gap split-wedge antenna, demonstrating its potential for sensing and spectroscopy applications.
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published
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Journal / series
Volume
16 (12)
Pages / Article No.
7849 - 7856
Publisher
American Chemical Society
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Subject
Optical antenna; Surface-enhanced Raman scattering (SERS); Template stripping; Gap plasmon; Atomic layer deposition; Atomic layer lithography
Organisational unit
03875 - Norris, David J. / Norris, David J.