Semiconductor Metasurfaces for Surface-enhanced Raman Scattering

TL;DR

This paper introduces a novel semiconductor metasurface platform using TiO2 and bound states in the continuum to significantly enhance surface-enhanced Raman scattering, overcoming previous limitations of weak electromagnetic confinement.

Contribution

The study develops a TiO2-based metasurface leveraging BICs to boost SERS activity, achieving high electromagnetic field enhancement and spectral tunability with earth-abundant materials.

Findings

Achieved electric field enhancement of |E/E0|^2 ~ 10^3.

Demonstrated spectral tunability of SERS using semiconductor metasurfaces.

Provided a new approach for bio-compatible and earth-abundant SERS substrates.

Abstract

Semiconductor-based surface-enhanced Raman spectroscopy (SERS) substrates, as a new frontier in the field of SERS, are hindered by their poor electromagnetic field confinement, and weak light-matter interaction. Metasurfaces, a class of 2D artificial materials based on the electromagnetic design of nanophotonic resonators, enable strong electromagnetic field enhancement and optical absorption engineering for a wide range of semiconductor materials. However, the engineering of semiconductor substrates into metasurfaces for improving SERS activity remains underexplored. Here, we develop an improved SERS metasurface platform that leverages the combination of titanium oxide (TiO2) and the emerging physical concept of optical bound states in the continuum (BICs) to boost the Raman emission. Moreover, fine-tuning of BIC-assisted resonant absorption offers a pathway for maximizing the photoinduced charge transfer effect (PICT) in SERS. We achieve ultrahigh values of BIC-assisted electric field enhancement (|E/E0|^2 ~ 10^3), challenging the preconception of weak electromagnetic (EM) field enhancement on semiconductor SERS substrates. Our BIC-assisted TiO2 metasurface platform offers a new dimension in spectrally-tunable SERS with earth-abundant and bio-compatible semiconductor materials, beyond the traditional plasmonic ones.