Controllable Doping Characteristics for WSxSey Monolayers Based on the Tunable S/Se Ratio

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 MoSxSey, MoxWyS2, MoxWySe2, and WSxSey monolayers that exhibit tunable band gap energies. However, few works have examined the doping behavior of those 2D monolayers. This study synthesizes WSxSey monolayers using the CVD process, in which different heating temperatures are applied to sulfur powders to control the ratio of S to Se in WSxSey. Increasing the Se component in WSxSey 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 WSxSey monolayers. In addition, Raman spectra showed a red shift of the WS2-related peaks, indicating n-doping behavior in the WSxSey monolayers. In contrast, with the increase of the sulfur component, the blue shift of the WSe2-related peaks in the Raman spectra involved the p-doping behavior of WSxSey monolayers. In addition, the optical band gap of the as-grown WSxSey 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 WSxSey monolayers provide more options in electronic and optical design.

Automated summary

Transition metal dichalcogenides have unique characteristics and potential applications in electronic devices. This study focuses on the doping behavior of WSxSey monolayers synthesized using the CVD process. Increasing the Se component leads to a transformation from p-type to n-type electronic state, while increasing the S component enhances the p-type characteristics. Raman spectra indicate n-doping behavior with a red shift in WS2-related peaks and p-doping behavior with a blue shift in WSe2-related peaks. The optical band gap of WSxSey monolayers can be precisely tuned through different chalcogenide heating temperatures.