Study on the Optical Properties of WS2 Thin Films Annealed in Various Atmospheres Including Ar, Ar/H2, NH3/H2O, and O2

In this study, tungsten disulfide nanostructures are synthesized on the Si/SiO2 substrates by thermal chemical vapor deposition in a three-zone furnace. For this purpose, sulfur and tungsten oxide powders are first placed under argon gas in the first and third regions of the furnace at 220 and 1100 °C, respectively. A scanning electron microscope is then used to evaluate the morphology of the grown layers. The images confirm the growth of WS2 hexagonal flakes. The samples are then placed in a ceramic plant in the center of a single-zone furnace for re-annealing. The grown layers are reheated under different gases of Argon, Argon/Hydrogen, Oxygen, and Ammonia/Water at 450 °C for 30 minutes. To evaluate the annealing effect, X-ray diffraction, Raman spectroscopy, and Ultraviolet-Visible spectroscopy are employed. The results confirmed the effect of the Argon/Hydrogen atmosphere on the improvement in the optical and crystalline properties of the WS2 synthesized layers.