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Using of Raman scattering and photoluminescence spectroscopies at variable temperature, we report a comprehensive characterization of a MoSe2 monolayer deposited onto hBN and capped by mono- and bilayer graphene. Along with the atomically flat hBN susbstrate, a single graphene epilayer is sufficient to passivate the MoSe2 layer and provides a homogenous environment without the need for an extra hBN capping layer. As a result, we do not observe photo-induced doping in our heterostructure and the MoSe2 photoluminescence linewidth gets as low as 1.8 meV, hence approaching the homo- geneous limit. The semi-metallic graphene layer neutralizes the 2D semiconductor and enables picosec- ond non-radiative energy transfer that quenches radiative recombination from long-lived states. As a result, emission from the neutral band edge exciton largely dominates the photoluminescence spectrum of the MoSe2/graphene heterostructure. Since this exciton has a picosecond radiative lifetime at low temperature, comparable with the energy transfer time, its emission is only quenched by a factor of 3 ± 1 and 4.5 ± 1 in the presence of mono- and bilayer graphene at liquid helium temperature. Finally, we exploit the valley- contrasting properties of monolayer TMDs and show that our simple van der Waals assembly provides a single-line 2D chiral emitter with degrees of valley polarization and coherence up to 22 ± 3 and 42 ± 3 at low temperature under excitation 60 meV above the bright exciton line.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: Van der Waals heterostructures, molybdenum diselenide, graphene

刊行年月日: 2022-03-08

出版者: Cellule MathDoc/Centre Mersenne

掲載誌:

• Comptes Rendus. Physique (ISSN: 18781535) vol. 22 issue. S4 p. 77-88

研究助成金:

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.5802/crphys.58

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更新時刻: 2025-02-26 12:30:36 +0900

MDRでの公開時刻: 2025-02-26 12:30:36 +0900