Scanning Tunneling Microscope-Induced Excitonic Luminescence of a Two-Dimensional Semiconductor

Delphine Pommier, Rémi Bretel, Luis E. Parra López, Florentin Fabre, Andrew Mayne, Elizabeth Boer-Duchemin, Gérald Dujardin, Guillaume Schull, Stéphane Berciaud, and Eric Le Moal
Phys. Rev. Lett. 123, 027402 – Published 10 July 2019
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Abstract

The long sought-after goal of locally and spectroscopically probing the excitons of two-dimensional (2D) semiconductors is attained using a scanning tunneling microscope (STM). Excitonic luminescence from monolayer molybdenum diselenide (MoSe2) on a transparent conducting substrate is electrically excited in the tunnel junction of an STM under ambient conditions. By comparing the results with photoluminescence measurements, the emission mechanism is identified as the radiative recombination of bright A excitons. STM-induced luminescence is observed at bias voltages as low as those that correspond to the energy of the optical band gap of MoSe2. The proposed excitation mechanism is resonance energy transfer from the tunneling current to the excitons in the semiconductor, i.e., through virtual photon coupling. Additional mechanisms (e.g., charge injection) may come into play at bias voltages that are higher than the electronic band gap. Photon emission quantum efficiencies of up to 107 photons per electron are obtained, despite the lack of any participating plasmons. Our results demonstrate a new technique for investigating the excitonic and optoelectronic properties of 2D semiconductors and their heterostructures at the nanometer scale.

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  • Received 13 December 2018

DOI:https://doi.org/10.1103/PhysRevLett.123.027402

© 2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Delphine Pommier1, Rémi Bretel1, Luis E. Parra López2, Florentin Fabre2, Andrew Mayne1, Elizabeth Boer-Duchemin1, Gérald Dujardin1, Guillaume Schull2, Stéphane Berciaud2, and Eric Le Moal1,*

  • 1Institut des Sciences Moléculaires d’Orsay, CNRS, Université Paris Sud, Université Paris-Saclay, F-91405 Orsay, France
  • 2Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France

  • *eric.le-moal@u-psud.fr

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Issue

Vol. 123, Iss. 2 — 12 July 2019

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