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

Abstract

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.

Authors:

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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+ Show Author Affiliations

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

Publication Date:

Wed Nov 30 00:00:00 EST 2016

Research Org.:

Univ. of Colorado, Boulder, CO (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1333971

Alternate Identifier(s):

OSTI ID: 1337514

Grant/Contract Number:  

FG02-06ER46348; 339905

Resource Type:

Published Article

Journal Name:

Nano Letters

Additional Journal Information:

Journal Name: Nano Letters Journal Volume: 16 Journal Issue: 12; Journal ID: ISSN 1530-6984

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

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