Single- and narrow-line photoluminescence in a boron nitride-supported MoSe<math>
  <msub><mrow></mrow> <mn>2</mn> </msub>
</math>/graphene heterostructure

Luis Enrique Parra López; Loïc Moczko; Joanna Wolff; Aditya Singh; Etienne Lorchat; Michelangelo Romeo; Takashi Taniguchi; Kenji Watanabe; Stéphane Berciaud

doi:10.5802/crphys.58

Article Single- and narrow-line photoluminescence in a boron nitride-supported MoSe

_{2}

/graphene heterostructure

Luis Enrique Parra López ; Loïc Moczko ; Joanna Wolff ; Aditya Singh ; Etienne Lorchat ; Michelangelo Romeo ; Takashi Taniguchi (National Institute for Materials Science) ; Kenji Watanabe (National Institute for Materials Science) ; Stéphane Berciaud

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Luis Enrique Parra López, Loïc Moczko, Joanna Wolff, Aditya Singh, Etienne Lorchat, Michelangelo Romeo, Takashi Taniguchi, Kenji Watanabe, Stéphane Berciaud. Single- and narrow-line photoluminescence in a boron nitride-supported MoSe

_{2}

/graphene heterostructure. Comptes Rendus. Physique. 2022, 22 (S4), 77-88. https://doi.org/10.5802/crphys.58

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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.

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