Vertically-Oriented WS 2 Nanosheets with a Few Layers and Its Raman Enhancements

Vertically-oriented two-dimensional (2D) tungsten disulfide (WS ) nanosheets were successfully grown on a Si substrate at a temperature range between and 550 °C via the direct chemical reaction between WCl 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 WS 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 WS nanosheets exhibited strong Raman enhancement effects up to 9.2 times greater than that on the exfoliated WS monolayer flake sample. From our results, we suggest that the WS nanosheets can be an effective surface-enhanced Raman scattering substrate for detecting target molecules.