Structural and Optical Properties of Tungsten Disulfide Nanoscale Films Grown by Sulfurization from W and WO(3)

Tungsten disulfide (WS(2)) was prepared from W metal and WO(3) by ion beam sputtering and sulfurization in a different number of layers, including monolayer, bilayer, six-layer, and nine-layer. To obtain better crystallinity, the nine-layer of WS(2) was also prepared from W metal and sulfurized in a furnace at different temperatures (800, 850, 900, and 950 °C). X-ray diffraction revealed that WS(2) has a 2-H crystal structure and the crystallinity improved with increasing sulfurization temperature, while the crystallinity of WS(2) sulfurized from WO(3) (WS(2)-WO(3)) is better than that sulfurized from W-metal (WS(2)-W). Raman spectra show that the full-width at half maximum (FWHM) of WS(2)-WO(3) is narrower than that of WS(2)-W. We demonstrate that high-quality monocrystalline WS(2) thin films can be prepared at wafer scale by sulfurization of WO(3). The photoluminescence of the WS(2) monolayer is strongly enhanced and centered at 1.98 eV. The transmittance of the WS(2) monolayer exceeds 80%, and the measured band gap is 1.9 eV, as shown by ultraviolet-visible-infrared spectroscopy.