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Exciton localization in MoSe₂ monolayer induced by adsorbed gas molecules

Venanzi, T.; Arora, H.; Erbe, A.; Pashkin, O.; Winnerl, S.; Helm, M.; Schneider, H.

Lattice defects and dielectric environment play a crucial role for 2D materials. Gas molecules can get physisorbed easily on the surface through van der Waals forces and can modify dramatically the electronic and optical properties. In this work we investigate the impact of the physisorbed gas molecules on the optical properties of MoSe₂ monolayers by means of low-temperature photoluminescence (PL). More specifically we focus on the physics of excitons localized by gas molecules. The associated PL peak is observed to show a systematic and large red-shift with temperature and a blue-shift with laser irradiation. Both energy shifts are explained in terms of thermal instability of the localization in combination with hopping effects. Finally a model is presented which can reproduce the experimental data with excellent agreement.

Keywords: MoSe2; photoluminescence; localized excitons; TMD; physisorption

Permalink: https://www.hzdr.de/publications/Publ-29321
Publ.-Id: 29321