Vertically-Oriented WS₂ Nanosheets with a Few Layers and Its Raman Enhancements

Vertically-oriented two-dimensional (2D) tungsten disulfide (WS₂) nanosheets were successfully grown on a Si substrate at a temperature range between and 550 °C via the direct chemical reaction between WCl₆ and S in the gas phase. The growth process was carefully optimized by adjusting temperature, the locations of reactants and substrate, and carrier gas flow. Additionally, vertically-oriented 2D WS₂ nanosheets with a few layers were tested as a surface-enhanced Raman scattering substrate for detecting rhodamine 6G (R6G) molecules where enhancement occurs from chemical enhancement by charge transfer transition from semiconductor). Raman spectra of R6G molecules adsorbed on vertically-oriented 2D WS₂ nanosheets exhibited strong Raman enhancement effects up to 9.2 times greater than that on the exfoliated WS₂ monolayer flake sample. From our results, we suggest that the WS₂ nanosheets can be an effective surface-enhanced Raman scattering substrate for detecting target molecules.