Exciton tuning in monolayer WSe2 via 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 WSe₂ via substrate induced electron doping

Nanoscale Adv. 2022 Oct 25;4(23):5102-5108. doi: 10.1039/d2na00495j. eCollection 2022 Nov 22.

Authors

Yang Pan^{1

2}, Mahfujur Rahaman³, Lu He^{1

2}, Ilya Milekhin^{1

2}, Gopinath Manoharan⁴, Muhammad Awais Aslam⁵, Thomas Blaudeck^{2

4

6}, Andreas Willert⁶, Aleksandar Matković⁵, Teresa I Madeira^{1

2}, Dietrich R T Zahn^{1

2}

Affiliations

¹ Semiconductor Physics, Institute of Physics, Chemnitz University of Technology Chemnitz Germany yang.pan@physik.tu-chemnitz.de.
² Center for Materials, Architectures, and Integration of Nanomembranes (MAIN), Chemnitz University of Technology Chemnitz Germany.
³ Department of Electrical and Systems Engineering, University of Pennsylvania Philadelphia PA USA.
⁴ Center for Microtechnologies, Chemnitz University of Technology Chemnitz Germany.
⁵ Institute of Physics, Montanuniversität Leoben Leoben Austria.
⁶ 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.