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Probing excitons, trions and dark excitons in monolayer WS2 using resonance Raman spectroscopy

Probing excitons, trions and dark excitons in monolayer WS2 using resonance Raman spectroscopy
Probing excitons, trions and dark excitons in monolayer WS2 using resonance Raman spectroscopy
We present temperature-dependent resonance Raman measurements on monolayer WS2 for the temperature range 4–295 K using excitation photon energies from 1.9 to 2.15 eV in ∼7 meV steps. These are analyzed to determine the resonance profiles of five previously assigned phonon based Raman peaks (A1′, E′, 2ZA, LA, 2LA) and a previously unassigned peak at 485 cm–1 whose possible attributions are discussed. The resonance profiles obtained are fitted to a perturbation theory derived model and it is shown that both excitons and trions are required to explain the profiles. The model is used to separate the contribution of exciton–exciton, trion–trion, and exciton–trion scattering to each of the Raman peaks at 4 K. This separation allows the ratios of the rates of scattering involving the A1′ and E′ phonons for each of the three types of scattering to be determined. The explanation of the multiphonon Raman peaks requires the coupling of bright excitons and trions to large wavevector dark states. The fitting of the resonance Raman profiles for these Raman peaks demonstrates scattering of bright excitons to bright trions via these large wavevector dark states.
1530-6984
McDonnell, Liam
f55afd9a-aa83-4a34-b3ac-c1b9ff3858b9
Smith, David
d9b2c02d-b7ea-498b-9ea1-208a1681536f
Huang, Chung-Che
825f7447-6d02-48f6-b95a-fa33da71f106
Hewak, Daniel
87c80070-c101-4f7a-914f-4cc3131e3db0
Cui, Qingsong
246f6604-fcb0-4052-b00b-677b08739083
McDonnell, Liam
f55afd9a-aa83-4a34-b3ac-c1b9ff3858b9
Smith, David
d9b2c02d-b7ea-498b-9ea1-208a1681536f
Huang, Chung-Che
825f7447-6d02-48f6-b95a-fa33da71f106
Hewak, Daniel
87c80070-c101-4f7a-914f-4cc3131e3db0
Cui, Qingsong
246f6604-fcb0-4052-b00b-677b08739083

McDonnell, Liam, Smith, David, Huang, Chung-Che, Hewak, Daniel and Cui, Qingsong (2018) Probing excitons, trions and dark excitons in monolayer WS2 using resonance Raman spectroscopy. Nano Letters. (doi:10.1021/acs.nanolett.7b05184).

Record type: Article

Abstract

We present temperature-dependent resonance Raman measurements on monolayer WS2 for the temperature range 4–295 K using excitation photon energies from 1.9 to 2.15 eV in ∼7 meV steps. These are analyzed to determine the resonance profiles of five previously assigned phonon based Raman peaks (A1′, E′, 2ZA, LA, 2LA) and a previously unassigned peak at 485 cm–1 whose possible attributions are discussed. The resonance profiles obtained are fitted to a perturbation theory derived model and it is shown that both excitons and trions are required to explain the profiles. The model is used to separate the contribution of exciton–exciton, trion–trion, and exciton–trion scattering to each of the Raman peaks at 4 K. This separation allows the ratios of the rates of scattering involving the A1′ and E′ phonons for each of the three types of scattering to be determined. The explanation of the multiphonon Raman peaks requires the coupling of bright excitons and trions to large wavevector dark states. The fitting of the resonance Raman profiles for these Raman peaks demonstrates scattering of bright excitons to bright trions via these large wavevector dark states.

Text Accepted Manuscript - Probing Excitons Trions and Dark Excitons in Monolayer WS2 - Accepted Manuscript
Restricted to Repository staff only until 3 January 2019.
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More information

Submitted date: 9 December 2017
Accepted/In Press date: 3 January 2018
e-pub ahead of print date: 3 January 2018

Identifiers

Local EPrints ID: 416941
URI: https://eprints.soton.ac.uk/id/eprint/416941
ISSN: 1530-6984
PURE UUID: e67370be-d0de-4a81-a508-4673fbc54317
ORCID for Chung-Che Huang: ORCID iD orcid.org/0000-0003-3471-2463
ORCID for Daniel Hewak: ORCID iD orcid.org/0000-0002-2093-5773

Catalogue record

Date deposited: 15 Jan 2018 17:30
Last modified: 06 Jun 2018 13:08

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