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Oxygen Passivation Mediated Tunability of Trion and Excitons in MoS2

TitleOxygen Passivation Mediated Tunability of Trion and Excitons in MoS2
Publication TypeJournal Article
Year of Publication2017
AuthorsGogoi, Pranjal Kumar, Hu Zhenliang, Wang Qixing, Carvalho Alexandra, Schmidt Daniel, Yin Xinmao, Chang Yung-Huang, Li Lain-Jong, Sow Chorng Haur, Neto Castro A. H., Breese Mark B. H., Rusydi Andrivo, and Wee Andrew T. S.
JournalPhys. Rev. Lett.
Date Published08/2017
Keywords2-dimensional semiconductors, approximation, defects, energy, molybdenum-disulfide, monolayer mos2, optical-absorption, optoelectronics, photoluminescence, transition-metal dichalcogenides

Using wide spectral range in situ spectroscopic ellipsometry with systematic ultrahigh vacuum annealing and in situ exposure to oxygen, we report the complex dielectric function of MoS2 isolating the environmental effects and revealing the crucial role of unpassivated and passivated sulphur vacancies. The spectral weights of the A (1.92 eV) and B (2.02 eV) exciton peaks in the dielectric function reduce significantly upon annealing, accompanied by spectral weight transfer in a broad energy range. Interestingly, the original spectral weights are recovered upon controlled oxygen exposure. This tunability of the excitonic effects is likely due to passivation and reemergence of the gap states in the band structure during oxygen adsorption and desorption, respectively, as indicated by ab initio density functional theory calculation results. This Letter unravels and emphasizes the important role of adsorbed oxygen in the optical spectra and many-body interactions of MoS2.


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