Platform for surface-enhanced Raman scattering in layered quantum materials

Raman spectroscopy has been used to study transition metal dichalcogenides (TMDs), quantum materials with promising properties. However, monolayer (1L) TMDs have limited observable Raman modes due to low light absorption. In this study, we propose a potential platform that can effectively enhance Raman scattering and increase the number of observable Raman modes in 1L TMDs. To enhance Raman scattering in 1L TMDs, a platform was fabricated by forming large-scale periodic arrays of gold micropillars (MPs) using conventional photolithography followed by gold film deposition. 1L WSe₂ was transferred onto the Au MPs and Raman scattering was observed. The Raman intensity of 1L WSe₂ on Au MPs was 19 times higher than that of 1L WSe₂ on SiO₂ plates, and Raman modes difficult to detect in typical 1L WSe₂ are observed. Confocal Raman spectroscopic mapping revealed that the strong local Raman enhancement at the edge of the Au MP resulted in the amplification of Raman scattering in 1L WSe₂ on Au MP. This local field enhancement was theoretically verified using finite difference time domain (FDTD). The platform has industrial advantages and wide applicability due to its low cost, simple process, large controllable area, and short process time.