Elsevier

Current Applied Physics

Volume 31, November 2021, Pages 16-21
Current Applied Physics

Gap plasmon modes resolved by ultraflat nanogap and linear polarization in terrace-stepped hexagonal boron nitride spacer sandwiched by Ag nanowire and metal substrates

https://doi.org/10.1016/j.cap.2021.07.008Get rights and content

Highlights

  • •

    Gap plasmon modes in terrace-stepped hBN spacer between Ag nanowire and Au film are investigated.

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    The polarization resolved excitation of gap plasmon modes in this hybrid is demonstrated.

  • •

    Polarized excitation of gap plasmon modes is resolved along the Ag nanowire of hybrid by unpolarized dark-field spectrum.

Abstract

We investigate the nanogap and polarization-resolved excitation of gap plasmon modes using terrace-stepped hexagonal boron nitride (hBN) sandwiched between Ag nanowires and Au substrates for a metal–insulator–metal gap structure. The gap plasmon modes in the proposed hybrid structure are dominantly excited by a P-polarized incident light, which is supported by full-wave numerical simulations. Plasmon mode evolution for various hBN spacer thicknesses ranging from 5 to 90 nm shows that optical signals acquired via unpolarized dark-field mapping spectroscopy are primarily due to the optical scattering of the P-polarized incident light. Moreover, this plasmonic mode changes significantly from gap plasmon mode to Fabry–Perot-type resonance in a hBN thickness of 50–90 nm. Our analysis reveals that the proposed hybrid structure based on Ag nanowires and stepped hBN provides a well-defined gap thickness and is a robust platform for analyzing gap plasmon modes.

Section snippets

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

This work was supported by the Technology Innovation Program (20005750, Commercial Development of Combustion System Control Technology for Minimizing Pollutant with Multiple Analysis) funded by the Ministry of Trade, Industry, & Energy (MOTIE, Republic of Korea). H.S.L. acknowledges the support by the Basic Science Research Program through the National Research Foundation of Korea (NRF) grant funded by the Ministry of Education (NRF-2018R1D1A1A02046206 and NRF-2021R1I1A3054688). K.-H.K.,

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