Double Ag Nanowires on a Bilayer MoS2 Flake for Surface-Enhanced Raman Scattering

Surface-enhanced Raman spectroscopy (SERS) of rhodamine 6G (R6G) was investigated using a hybrid nanostructure of double-aligned Ag nanowires (AgNWs) on a bilayer triangular MoS2 flake under excitation of polarized light. Enhanced R6G Raman signatures were achieved on the hybrid AgNWs–MoS2 SERS substrates as compared to the AgNWs-only ones. Moreover, the polarization has been found to affect not only the Raman intensities of R6G and MoS2 on both SERS substrates but also the R6G Raman enhancement factor on the hybrid AgNWs–MoS2 SERS substrate. Specifically, this enhancement was found to be the largest (lowest) when the polarization is perpendicular (parallel) to the axial direction of the aligned AgNWs. In addition, a theoretical simulation has revealed that the SERS enhancement by the MoS2 in the hybrid AgNWs–MoS2 SERS substrates is primarily attributed to the enhanced evanescent electric field of the hot spot at the interface between AgNWs and MoS2.