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 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 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 MoS2.
@article{arxiv.1707.06348,
title = {Oxygen passivation mediated tunability of trion and excitons in MoS$_2$},
author = {Pranjal Kumar Gogoi and Zhenliang Hu and Qixing Wang and Alexandra Carvalho and Daniel Schmidt and Xinmao Yin and Yung-Huang Chang and Lain-Jong Li and Chorng Haur Sow and A. H. Castro Neto and Mark B. H. Breese and Andrivo Rusydi and Andrew T. S. Wee},
journal= {arXiv preprint arXiv:1707.06348},
year = {2017}
}
Comments
Accepted in Physical Review Letters; Main Article: 6 pages, 4 figures; Supplemental Material: 6 pages, 7 figures, 10 tables