Oxygen passivation mediated tunability of trion and excitons in MoS${}_2$

Abstract

Using wide spectral range in situ spectroscopic ellipsometry with systematic ultra high vacuum annealing and in situ exposure to oxygen, we report the complex dielectric function of MoS${}_2$ 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 bandstructure during oxygen adsorption and desorption, respectively, as indicated by ab initio density functional theory calculation results. This work unravels and emphasizes the important role of adsorbed oxygen in the optical spectra and many-body interactions of MoS${}_2$.

Accepted in Physical Review Letters; Main Article: 6 pages, 4 figures; Supplemental Material: 6 pages, 7 figures, 10 tables

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• Effect of strain and sulfur vacancies on the luminescence and valley polarization properties of CVD grown monolayer MoS${}_2$ films
• Effect of manganese incorporation on the excitonic recombination dynamics in monolayer MoS${}_2$
• Momentum Conserved Ultrafast Charge Transfer Dynamics of Interlayer Excitons in vdW Heterostructures
• Interfacial Polarons Driven by Charge Transfer In WSe2/Cuprate Superconductor Systems