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

Abstract

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. 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 $\mu$W/$\mu$m${}^2$ 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.

16 pages, 5 figures

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Cited by in corpus (27)

• Excitonic linewidth approaching the homogeneous limit in MoS2 based van der Waals heterostructures : accessing spin-valley dynamics
• Brightening of dark excitons in monolayers of semiconducting transition metal dichalcogenides
• Direct exciton emission from atomically thin transition metal dichalcogenide heterostructures near the lifetime limit
• Optical response of monolayer, few-layer and bulk tungsten disulfide
• Filtering the photoluminescence spectra of atomically thin semiconductors with graphene
• Near-unity light absorption in a monolayer WS2 van der Waals heterostructure cavity
• Charge versus energy transfer in atomically-thin graphene-transition metal dichalcogenide van der Waals heterostructures
• Robust valley polarization of helium ion modified atomically thin MoS${}_2$
• Influence of the effective layer thickness on the groundstate and excitonic properties of transition-metal dichalcogenide systems
• The interplay between excitons and trions in a monolayer of MoSe${}_2$
• Valley polarized relaxation and upconversion luminescence from Tamm-Plasmon Trion-Polaritons with a MoSe2 monolayer
• Second- and third-order optical susceptibilities in bidimensional semiconductors near excitons states
• Radiative lifetime of localized excitons in transition metal dichalcogenides
• Optical identification using imperfections in 2D materials
• Suppressed out-of-plane polarizability of free excitons in monolayer WSe${}_2$
• Isotropic conduction and negative photoconduction in ultrathin PtSe${}_2$ films
• Spectrally narrow exciton luminescence from monolayer MoS2 exfoliated onto epitaxially grown hexagonal BN
• Substrate engineering for high quality emission of free and localized excitons from atomic monolayers in hybrid architectures
• Tuning carrier concentration in a superacid treated MoS${}_2$ monolayer
• Extrinsic localized excitons in patterned 2D semiconductors
• Optical properties of exciton in two-dimensional transition metal dichalcogenide nanobubbles
• Direct Observation of Intravalley Phonon Scattering of 2s Excitons in MoSe${}_2$ and WSe${}_2$ Monolayers
• The Structure and Dispersion of Exciton-Trion-Polaritons in Two-Dimensional Materials: Experiments and Theory
• Probing the optical near-field interaction of Mie nanoresonators with atomically thin semiconductors
• Imaging Seebeck drift of excitons and trions in MoSe2 monolayers
• Valley-dependent emission patterns enabled by plasmonic nanoantennas
• Heteroepitaxial growth of high optical quality, wafer-scale van der Waals heterostrucutres