| Summary: | Transition metal dichalcogenides (TMDs) have attracted much attention because of their unique characteristics and potential applications in electronic devices. Recent reports have successfully demonstrated the growth of 2-dimensional MoS<sub>x</sub>Se<sub>y</sub>, Mo<sub>x</sub>W<sub>y</sub>S<sub>2</sub>, Mo<sub>x</sub>W<sub>y</sub>Se<sub>2</sub>, and WS<sub>x</sub>Se<sub>y</sub> monolayers that exhibit tunable band gap energies. However, few works have examined the doping behavior of those 2D monolayers. This study synthesizes WS<sub>x</sub>Se<sub>y</sub> monolayers using the CVD process, in which different heating temperatures are applied to sulfur powders to control the ratio of S to Se in WS<sub>x</sub>Se<sub>y</sub>. Increasing the Se component in WS<sub>x</sub>Se<sub>y</sub> monolayers produced an apparent electronic state transformation from p-type to n-type, recorded through energy band diagrams. Simultaneously, p-type characteristics gradually became clear as the S component was enhanced in WS<sub>x</sub>Se<sub>y</sub> monolayers. In addition, Raman spectra showed a red shift of the WS<sub>2</sub>-related peaks, indicating n-doping behavior in the WS<sub>x</sub>Se<sub>y</sub> monolayers. In contrast, with the increase of the sulfur component, the blue shift of the WSe<sub>2</sub>-related peaks in the Raman spectra involved the p-doping behavior of WS<sub>x</sub>Se<sub>y</sub> monolayers. In addition, the optical band gap of the as-grown WS<sub>x</sub>Se<sub>y</sub> monolayers from 1.97 eV to 1.61 eV is precisely tunable via the different chalcogenide heating temperatures. The results regarding the doping characteristics of WS<sub>x</sub>Se<sub>y</sub> monolayers provide more options in electronic and optical design.
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