Phonon induced luminescence decay in monolayer MoS2 on SiO2/Si substrates

Saigal, Nihit; Ghosh, Sandip

doi:10.1063/1.4938141

Cited by 19 publications

(14 citation statements)

References 28 publications

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“…The tube surface remains clear after manipulations, without any contaminations. Importantly, the use of free‐standing samples excluded the possible effect of a substrate . Besides, it permitted us to perform the TEM characterization of selected tubes to obtain information on their structural properties.…”

Section: Experimental Details and Samples Characterizationmentioning

confidence: 99%

Excitonic Emission in van der Waals Nanotubes of Transition Metal Dichalcogenides

et al. 2019

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Nanotubes (NTs) of transition metal dichalcogenides (TMDs), were first synthesized more than a quarter of a century ago; nevertheless, many of their optical properties have so far remained basically unknown. Herein, the state of the art in the knowledge of the optical properties of TMD NTs is presented. First, general properties of multilayered crystals are evaluated, and available data on related NTs are analyzed. Then, the technology for the formation and the structural characteristics of NTs are represented, focusing on the structures synthesized by chemical transport reaction. The core of this work is the presentation of the ability of synthesized TMD NTs to emit bright photoluminescence (PL), which has been discovered recently. By means of micro-PL spectroscopy of individual tubes, we show that excitonic transitions relevant to both direct and indirect band gaps contribute to the emission spectra of the NTs despite having the dozens of monolayers in their walls. The performance of the tubes as efficient optical resonators is highlighted, where confined optical modes strongly affect the emission. Finally, a brief conclusion is presented, along with an outlook of the future studies of this novel radiative member of the NTs family, which have unique potential for different nanophotonics applications.

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Section: Experimental Details and Samples Characterizationmentioning

confidence: 99%

Excitonic Emission in van der Waals Nanotubes of Transition Metal Dichalcogenides

et al. 2019

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“…A small peak around 255 cm −1 is due to the optical branch consisting of both in-plane (W atoms) and out-of plane (Se atoms) torsional modes, but effective only by about 25% compared to the former. This is in stark difference found in MoS 2 ML A-exciton buildup where the main contribution comes from the optical branch around 400 cm −1 [40,49]. The B exciton couples in a similar manner with almost one-third contribution from optical branches.…”

Section: Resultsmentioning

confidence: 74%

Exciton-Phonon Coupling and Band-Gap Renormalization in Monolayer WSe$_{2}$

Mishra,

Bose,

Dhar

et al. 2018

Preprint

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Using a fully ab-initio methodology, we demonstrate how the lattice vibrations couple with neutral excitons in monolayer WSe2 and contribute to the non-radiative excitonic lifetime. We show that only by treating the electron-electron and electron-phonon interactions at the same time it is possible to obtain an unprecedented agreement of the zero and finite-temperature optical gaps and absorption spectra with the experimental results. The bare energies were calculated by solving the Kohn-Sham equations, whereas G0W0 many body perturbation theory was used to extract the excited state energies. A coupled electron-hole Bethe-Salpeter equation was solved incorporating the polaronic energies to show that it is the in-plane torsional acoustic phonon branch that contributes mostly to the A and B exciton build-up. We find that the three A, B and C excitonic peaks exhibit different behaviour with temperature, displaying different non-radiative linewidths. There is no considerable transition in the strength of the excitons with temperature but A-exciton exhibits darker nature in comparison to C-exciton. Further, all the excitonic peaks redshifts as temperature rises. Renormalization of the bare electronic energies by phonon interactions and the anharmonic lattice thermal expansion causes a decreasing band-gap with increasing temperature. The zero point energy renormalization (31 meV) is found to be entirely due to the polaronic interaction with negligible contribution from lattice anharmonicites. These findings may find a profound impact on electronic and optoelectronic device technologies based on these monolayers.

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“…It shows several interesting physical phenomena such as, a direct bandgap leading to efficient photoluminescence (PL) 1,2 , many body physical effects eg. observation of trions 3 and biexcitons 4 , spin-valley coupling 5,6 , exciton-phonon coupling 7,8 etc. State-of-the-art devices like field effect transistors, solar cells, light emitting diodes etc.…”

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confidence: 99%

“…Note that we do not fit the data for the sample with 130 s of Li exposure because its PL has almost entirely vanished and the spectrum is dominated by background of the Raman signal. Also, the fits are not ideal because apart from the exciton transition, the PL may have contribution from an unresolved trion related transition 3,8,3.…”

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confidence: 99%

Effect of lithium doping on the optical properties of monolayer MoS2

Saigal

Wielert

Čapeta

et al. 2018

Applied Physics Letters

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The effect of Lithium atoms evaporation on the surface of monolayer MoS 2 grown on SiO 2 /Si substrate is studied using ultra high vacuum (UHV ∼ 10 −11 mbar) Raman and circularly polarized photoluminescence spectroscopies, at low Lithium coverage (up to ∼0.17 monolayer). With increasing Li doping, the dominant E 1 2g and A 1g Raman modes of MoS 2 shift in energy and broaden. Additionally, non zone-center phonon modes become Raman active. This regards in particular to double resonance Raman scattering processes, involving longitudinal acoustic (LA) phonon modes at the M and K points of the Brillouin zone of MoS 2 and defects. It is also accompanied by significant decrease in the overall intensity and the degree of circular polarization of the photoluminescence spectrum. The observed changes in the optical spectra are understood as a result of electron doping by Lithium atoms and disorder-activated intervalley scattering of electrons and holes in the electronic band structure of monolayer MoS 2 .

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Phonon induced luminescence decay in monolayer MoS2 on SiO2/Si substrates

Cited by 19 publications

References 28 publications

Excitonic Emission in van der Waals Nanotubes of Transition Metal Dichalcogenides

Excitonic Emission in van der Waals Nanotubes of Transition Metal Dichalcogenides

Exciton-Phonon Coupling and Band-Gap Renormalization in Monolayer WSe$_{2}$

Effect of lithium doping on the optical properties of monolayer MoS2

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