Split-Wedge Antennas with Sub-5 nm Gaps for Plasmonic Nanofocusing

Journal Article · Wed Nov 30 00:00:00 EST 2016 · Nano Letters

DOI:https://doi.org/10.1021/acs.nanolett.6b04113· OSTI ID:1333971

Chen, Xiaoshu ^[1]; Lindquist, Nathan C. ^[2]; Klemme, Daniel J. ^[1]; Nagpal, Prashant ^[3]; Norris, David J. ^[4]; Oh, Sang-Hyun ^[1]

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1. Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
2. Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States, Physics Department, Bethel University, Saint Paul, Minnesota 55112, United States
3. Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80303, United States
4. Optical Materials Engineering Laboratory, ETH Zurich, 8092 Zurich, Switzerland

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 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.

• Research Organization: Univ. of Colorado, Boulder, CO (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: FG02-06ER46348; 339905
• OSTI ID: 1333971
• Alternate ID(s): OSTI ID: 1337514
• Journal Information: Nano Letters, Journal Name: Nano Letters Vol. 16 Journal Issue: 12; ISSN 1530-6984
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

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