Enhancing Raman spectra by coupling plasmons and excitons for large area MoS₂ monolayers

Surface-enhanced Raman spectroscopy (SERS) has been applied to analyze 2D materials with plasmonic enhancement at hotspots, localized at gaps or junctions. However, the SERS technique strongly demands hotspots at excitation laser wavelengths to achieve energy confinement at the excitation wavelength. In this study, we report the enhancement of Raman signals by the plasmon-exciton coupling between large-area monolayer MoS₂ and plasmonic nanogrooves (NGs). The plasmon-exciton coupling enhances Raman signal instead of SERS enhancement at an excitation wavelength. In addition, spectrally tunable plasmonic NGs are utilized to investigate coupled and de-coupled enhancements. The enhancement performance is further examined through electromagnetic field enhancement. We demonstrate that the proposed nanostructures integrated with atomically thin 2D materials, showing highly uniform Raman signals, are applicable for broad applications in materials science and nanophotonic.