Dependence of the photoelectric performance of the CVD-grown 2D WS₂ on the oxygen-doping concentration

Two-dimensional transition metal dichalcogenides (2D TMDCs) are considered as candidate materials for the next generation of nanoscale electronic and optoelectronic devices because of their unique properties. However, the reported photoelectric performances of 2D TMDCs vary dramatically and the reason for the variation in the photoelectric performance remains unclear. In this paper, the mechanism for the variation in the photoelectric performance of the photodetector based on the CVD-grown WS₂ is investigated. It is found that triangle monolayer WS₂ with a size of 100 µm can be grown on sapphire substrate by adopting the CVD method. Besides, monolayer WS₂ can be transferred from sapphire substrate onto Si/SiO₂ substrate with polymethyl methacrylate (PMMA) and polydimethylsiloxane (PDMS) as the intermediates. Oxygen doping and sulfurization have significant effect on the photoresponsivity of the CVD-grown WS₂. The photoresponsivity of the CVD-grown 2D WS₂ depends not only on the oxygen-doping concentration but also on the light wavelength. The CVD-grown WS₂ contains oxygen under the current experiment condition. Sulfurization can make the oxygen-doping concentration of the CVD-grown WS₂ decrease while oxygen doping can make it increase. The reported difference in photoelectric performance of the photodetector based on CVD-grown WS₂ is caused by the difference in the doping concentration.