Abstract
Surface-enhanced Raman scattering (SERS) is commonly associated with metal nanostructures. However, recently large Raman enhancement has also been reported for two-dimensional (2D) semiconductors. In the present work, we exam systematically the influence of thin 2D molybdenum disulfide (MoS2) films on the SERS properties of a typical silver (Ag) nanocavity formed by a single Ag nanoparticle (NP) and a flat Ag surface. The dependence of the localized electric field, Raman enhancement and spatial resolution on the NP-MoS2 film distance, the thickness of MoS2 film, as well as the NP radius were quantitatively calculated and analyzed. The results show that the presence of MoS2 film could efficiently enhance the plasmonic coupling between the NP and the substrate, leading to more significant SERS enhancement. Thinner MoS2 film and shorter NP-film distance will further improve the localized plasmonic enhancement. The calculated Raman enhancement factor reaches 9.1 ×1010 with monolayer MoS2 film under the 660-nm excitation. We also show that the spatial resolution for Raman spectroscopy could be significantly improved by reducing the NP radius, and the maximum resolutions is 4.5 nm at the radius size of 20 nm. Our results offer a theoretical guidance for better understanding the SERS properties of the novel 2D material and its further applications.
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