Oxygen Passivation Induced Tunability of Trion and Excitons in Molybdenum Disulphide

ORAL

Abstract

Molybdenum disulphide (MoS2) plays a central role in the burgeoning field of two-dimensional (2D) materials. Particularly, it has extraordinary optical properties which relies on strong electron-hole interactions. However, experimental reports as well as fundamental understanding of the optical properties isolating the roles of both defects and extrinsic environmental factors are still lacking for MoS2. We have performed in situ spectroscopic ellipsometry in a wide spectral range and under ultra-high vacuum (UHV) conditions to explore the complex dielectric function of MoS2. Combining high temperature UHV annealing and oxygen exposure, we show tunability of the exciton and trion features of the optical spectra. We attribute these tunability to desorption and chemisorption of oxygen upon UHV annealing and oxygen exposure, respectively. Ab initio density functional theory calculations suggest that oxygen chemisorption passivates gap states originating from sulphur vacancies, which influences the recovery of the exciton and trion features. Overall, this study highlights the importance of adsorbed oxygen as well as defects in the interpretation of experimental results from MoS2.

*ASTAR Pharos Grant, Singapore NRF, Singapore MOE, FRC, Medium Sized Centre Programme and CRP Grant

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Presenters

  • Pranjal Kumar Gogoi

    • Department of Physics, National University of Singapore

Authors

  • Pranjal Kumar Gogoi

    • Department of Physics, National University of Singapore

  • zhenliang Hu

    • Department of Physics, National University of Singapore

  • Qixing Wang

    • Physics, National University of Singapore
    • Department of Physics, National University of Singapore

  • Alexandra Carvalho

    • Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore

  • Daniel Schmidt

    • Singapore Synchrotron Light Source, National University of Singapore

  • Xinmao Yin

    • Physics, National University of Singapore
    • Department of Physics, National University of Singapore

  • Yung-Huang Chang

    • Department of Electrophysics, National Chiao Tung University

  • Lain-Jong Li

    • Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST)

  • Chorng Haur Sow

    • Department of Physics, National University of Singapore

  • Antonio Helio Castro Neto

    • Physics, National University of Singapore
    • Centre for Advanced 2D Materials and Graphene Research Centre
    • Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore

  • Mark Breese

    • Singapore Synchrotron Light Source, National University of Singapore

  • Andrivo Rusydi

    • Natl Univ of Singapore
    • Physics, National University of Singapore
    • Singapore Synchrotron Light Source
    • Department of Physics, National University of Singapore

  • Andrew Wee

    • Physics, National University of Singapore
    • Department of Physics, National University of Singapore