Using Si/MoS₂ Core-Shell Nanopillar Arrays Enhances SERS Signal

Two-dimensional layered material Molybdenum disulfide (MoS₂) exhibits a flat surface without dangling bonds and is expected to be a suitable surface-enhanced Raman scattering (SERS) substrate for the detection of organic molecules. However, further fabrication of nanostructures for enhancement of SERS is necessary because of the low detection efficiency of MoS₂. In this paper, period-distribution Si/MoS₂ core/shell nanopillar (NP) arrays were fabricated for SERS. The MoS₂ thin films were formed on the surface of Si NPs by sulfurizing the MoO₃ thin films coated on the Si NP arrays. Scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were performed to characterize Si/MoS₂ core-shell nanostructure. In comparison with a bare Si substrate and MoS₂ thin film, the use of Si/MoS₂ core-shell NP arrays as SERS substrates enhances the intensity of each SERS signal peak for Rhodamine 6G (R6G) molecules, and especially exhibits about 75-fold and 7-fold enhancements in the 1361 cm^-1 peak signal, respectively. We suggest that the Si/MoS₂ core-shell NP arrays with larger area could absorb more R6G molecules and provide larger interfaces between MoS₂ and R6G molecules, leading to higher opportunity of charge transfer process and exciton transitions. Therefore, the Si/MoS₂ core/shell NP arrays could effectively enhance SERS signal and serve as excellent SERS substrates in biomedical detection.