Observation of Multi-Phonon Emission in Monolayer WS<sub>2</sub> on Various Substrates
Transition metal dichalcogenides (TMDs) have unique absorption and emission properties that stem from their large excitonic binding energies, reduced-dielectric screening, and strong spin–orbit coupling. However, the role of substrates, phonons, and material defects in the excitonic scattering proce...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-12-01
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| Series: | Nanomaterials |
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| Online Access: | https://www.mdpi.com/2079-4991/14/1/37 |
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| author | Eli R. Adler Thy Doan Mai Le Ibrahim Boulares Robert Boyd Yangchen He Daniel Rhodes Edward Van Keuren Paola Barbara Sina Najmaei |
| author_facet | Eli R. Adler Thy Doan Mai Le Ibrahim Boulares Robert Boyd Yangchen He Daniel Rhodes Edward Van Keuren Paola Barbara Sina Najmaei |
| author_sort | Eli R. Adler |
| collection | DOAJ |
| description | Transition metal dichalcogenides (TMDs) have unique absorption and emission properties that stem from their large excitonic binding energies, reduced-dielectric screening, and strong spin–orbit coupling. However, the role of substrates, phonons, and material defects in the excitonic scattering processes remains elusive. In tungsten-based TMDs, it is known that the excitons formed from electrons in the lower-energy conduction bands are dark in nature, whereas low-energy emissions in the photoluminescence spectrum have been linked to the brightening of these transitions, either via defect scattering or via phonon scattering with first-order phonon replicas. Through temperature and incident-power-dependent studies of WS<sub>2</sub> grown by CVD or exfoliated from high-purity bulk crystal on different substrates, we demonstrate that the strong exciton–phonon coupling yields brightening of dark transitions up to sixth-order phonon replicas. We discuss the critical role of defects in the brightening pathways of dark excitons and their phonon replicas, and we elucidate that these emissions are intrinsic to the material and independent of substrate, encapsulation, growth method, and transfer approach. |
| first_indexed | 2024-03-08T15:00:07Z |
| format | Article |
| id | doaj.art-2b7b6caa40744f49a70fb365600b4105 |
| institution | Directory Open Access Journal |
| issn | 2079-4991 |
| language | English |
| last_indexed | 2024-03-08T15:00:07Z |
| publishDate | 2023-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Nanomaterials |
| spelling | doaj.art-2b7b6caa40744f49a70fb365600b41052024-01-10T15:04:51ZengMDPI AGNanomaterials2079-49912023-12-011413710.3390/nano14010037Observation of Multi-Phonon Emission in Monolayer WS<sub>2</sub> on Various SubstratesEli R. Adler0Thy Doan Mai Le1Ibrahim Boulares2Robert Boyd3Yangchen He4Daniel Rhodes5Edward Van Keuren6Paola Barbara7Sina Najmaei8Department of Physics, Georgetown University, Washington, DC 20057, USADepartment of Physics, Georgetown University, Washington, DC 20057, USAU.S. Army Combat Capabilities Development Command, Army Research Laboratory, Adelphi, MD 20783, USADepartment of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USADepartment of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USADepartment of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USADepartment of Physics, Georgetown University, Washington, DC 20057, USADepartment of Physics, Georgetown University, Washington, DC 20057, USAU.S. Army Combat Capabilities Development Command, Army Research Laboratory, Adelphi, MD 20783, USATransition metal dichalcogenides (TMDs) have unique absorption and emission properties that stem from their large excitonic binding energies, reduced-dielectric screening, and strong spin–orbit coupling. However, the role of substrates, phonons, and material defects in the excitonic scattering processes remains elusive. In tungsten-based TMDs, it is known that the excitons formed from electrons in the lower-energy conduction bands are dark in nature, whereas low-energy emissions in the photoluminescence spectrum have been linked to the brightening of these transitions, either via defect scattering or via phonon scattering with first-order phonon replicas. Through temperature and incident-power-dependent studies of WS<sub>2</sub> grown by CVD or exfoliated from high-purity bulk crystal on different substrates, we demonstrate that the strong exciton–phonon coupling yields brightening of dark transitions up to sixth-order phonon replicas. We discuss the critical role of defects in the brightening pathways of dark excitons and their phonon replicas, and we elucidate that these emissions are intrinsic to the material and independent of substrate, encapsulation, growth method, and transfer approach.https://www.mdpi.com/2079-4991/14/1/37two-dimensional materialstransition metal dichalcogenidesdark excitons |
| spellingShingle | Eli R. Adler Thy Doan Mai Le Ibrahim Boulares Robert Boyd Yangchen He Daniel Rhodes Edward Van Keuren Paola Barbara Sina Najmaei Observation of Multi-Phonon Emission in Monolayer WS<sub>2</sub> on Various Substrates Nanomaterials two-dimensional materials transition metal dichalcogenides dark excitons |
| title | Observation of Multi-Phonon Emission in Monolayer WS<sub>2</sub> on Various Substrates |
| title_full | Observation of Multi-Phonon Emission in Monolayer WS<sub>2</sub> on Various Substrates |
| title_fullStr | Observation of Multi-Phonon Emission in Monolayer WS<sub>2</sub> on Various Substrates |
| title_full_unstemmed | Observation of Multi-Phonon Emission in Monolayer WS<sub>2</sub> on Various Substrates |
| title_short | Observation of Multi-Phonon Emission in Monolayer WS<sub>2</sub> on Various Substrates |
| title_sort | observation of multi phonon emission in monolayer ws sub 2 sub on various substrates |
| topic | two-dimensional materials transition metal dichalcogenides dark excitons |
| url | https://www.mdpi.com/2079-4991/14/1/37 |
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