Exciton tuning in monolayer WSe2via substrate induced electron doping

Yang Pan; Mahfujur Rahaman; Lu He; Ilya Milekhin; Gopinath Manoharan; Muhammad Awais Aslam; Thomas Blaudeck; Andreas Willert; Aleksandar Matković; Teresa I. Madeira; Dietrich R. T. Zahn

doi:10.1039/D2NA00495J

Exciton tuning in monolayer WSe₂via substrate induced electron doping†

Yang Pan,

*^ab Mahfujur Rahaman,

^c Lu He,^ab Ilya Milekhin,^ab Gopinath Manoharan,^d Muhammad Awais Aslam,

^e Thomas Blaudeck,^bdf Andreas Willert,

^f Aleksandar Matković,^e Teresa I. Madeira^ab and Dietrich R. T. Zahn

^ab

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* Corresponding authors

^a Semiconductor Physics, Institute of Physics, Chemnitz University of Technology, Chemnitz, Germany
E-mail: yang.pan@physik.tu-chemnitz.de

^b Center for Materials, Architectures, and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, Chemnitz, Germany

^c Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA, USA

^d Center for Microtechnologies, Chemnitz University of Technology, Chemnitz, Germany

^e Institute of Physics, Montanuniversität Leoben, Leoben, Austria

^f Fraunhofer Institute for Electronic Nano Systems, Chemnitz, Germany

Abstract

We report large exciton tuning in WSe₂ monolayers via substrate induced non-degenerate doping. We observe a redshift of ∼62 meV for the A exciton together with a 1–2 orders of magnitude photoluminescence (PL) quenching when the monolayer WSe₂ is brought in contact with highly oriented pyrolytic graphite (HOPG) compared to dielectric substrates such as hBN and SiO₂. As the evidence of doping from HOPG to WSe₂, a drastic increase of the intensity ratio of trions to neutral excitons was observed. Using a systematic PL and Kelvin probe force microscopy (KPFM) investigation on WSe₂/HOPG, WSe₂/hBN, and WSe₂/graphene, we conclude that this unique excitonic behavior is induced by electron doping from the substrate. Our results propose a simple yet efficient way for exciton tuning in monolayer WSe₂, which plays a central role in the fundamental understanding and further device development.

This article is part of the themed collection: Celebrating nanoscience in Germany

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Exciton tuning in monolayer WSe₂via substrate induced electron doping†

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