Ultra-low power threshold for laser induced changes in optical properties of 2D molybdenum dichalcogenides

Fabian Cadiz, Cedric Robert, Gang Wang, Wilson Kong, Xi Fan, Mark Blei, Delphine Lagarde, Maxime Gay, Marco Manca, Takashi Taniguchi, Kenji Watanabe, Thierry Amand, Xavier Marie, Pierre Renucci, Sefaattin Tongay, Bernhard Urbaszek

Research output: Contribution to journalArticlepeer-review

65 Scopus citations


The optical response of traditional semiconductors depends on the laser excitation power used in experiments. For two-dimensional (2D) semiconductors, laser excitation effects are anticipated to be vastly different due to complexity added by their ultimate thinness, high surface to volume ratio, and laser-membrane interaction effects. We show in this article that under laser excitation the optical properties of 2D materials undergo irreversible changes in vacuum. Most surprisingly these effects take place even at low steady state excitation, which is commonly thought to be non-intrusive. In low temperature photoluminescence (PL) we show for monolayer (ML) MoSe2 samples grown by different techniques that laser treatment increases significantly the trion (i.e. charged exciton) contribution to the emission compared to the neutral exciton emission. Comparison between samples exfoliated onto different substrates shows that laser induced doping is more efficient for ML MoSe2 on SiO2/Si compared to h-BN and gold. For ML MoS2 we show that exposure to laser radiation with an average power in the μW μm-2 range does not just increase the trion-to-exciton PL emission ratio, but may result in the irreversible disappearance of the neutral exciton PL emission and a shift of the main PL peak to lower energy.

Original languageEnglish (US)
Article number045008
Journal2D Materials
Issue number4
StatePublished - Oct 12 2016


  • Doping
  • MoS
  • MoSe
  • Optical properties
  • Photoluminescence

ASJC Scopus subject areas

  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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