Plasmon localization and giant fields in holographic metasurface for SERS sensors

TL;DR

This paper introduces a holographic metasurface with plasmon localization that significantly enhances local electromagnetic fields, enabling sensitive SERS detection of molecules with a detection limit of 230 nM.

Contribution

It presents a novel metal holographic metasurface design that acts as an open plasmon resonator, demonstrating large field enhancement and practical SERS sensing capabilities.

Findings

Large local electromagnetic fields predicted and experimentally confirmed.

Achieved a SERS detection limit of 230 nM for specific molecules.

Demonstrated effective fabrication on a 4-inch silicon wafer.

Abstract

We present SERS-active metal holographic 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-inch Si wafer. The enhancement of the local electric field results in surface-enhanced Raman scattering (SERS). To investigate the SERS effect, the metasurfaces are covered by molecules of 4-mercaptophenylboronic acid, which form covalent bonds with the silver nanolayer and serve as a proof-of-concept. Finally, we obtain a detection limit of 230 nM for molecules of 4-mercaptophenylboronic acid.