Plasmon Localization and Giant Fields in an Open-Resonator Metasurface for Surface-Enhanced-Raman-Scattering Sensors

We present metal-dielectric metasurfaces fabricated from metal periodical nanograting deposited on a dielectric substrate. The metasurface consists of a modulated dielectric, which is covered by a thin silver layer. The metasurface operates as an open plasmon resonator. The theory of plasmons excited in the open resonator formed by a metal nanograting is presented. The large local electromagnetic field is predicted for optical frequencies. The excitation of plasmons is experimentally demonstrated in the metasurface designed on a 4-in. Si wafer. The enhancement of the local electric field results in surface-enhanced Raman scattering (SERS). To investigate the SERS effect, the metasurface is covered with a thin layer of the 4-mercaptophenylboronic acid that molecules form covalent bonds with the silver nanolayer. The enhancement of the Raman scattering serves as a proof of concept. We obtain a detection limit of 230 nM for molecules of 4-mercaptophenylboronic acid.

Automated summary

This study presents the design and fabrication of metal-dielectric metasurfaces, as well as their application in the excitation of plasmons and surface-enhanced Raman scattering. By utilizing the periodic arrangement of metal nanogratings on a dielectric substrate, an open plasmon resonator is formed, leading to the enhancement of the local electromagnetic field at optical frequencies.