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.