Journal
NANO LETTERS
Volume 15, Issue 8, Pages 5033-5038Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.5b01055
Keywords
2D materials; heterostructures; transition metal dichalcogenides; lifetime broadening; charge transfer
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Funding
- National Science Foundation [DMR-1124894, DGE-1144155, DGE-1069240]
- W. M. Keck Foundation
- Alexander von Humboldt Foundation
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We have applied optical absorption spectroscopy to investigate van der Waals heterostructures formed of pairs of monolayer transition metal dichalcogenide crystals, choosing MoS2/WS2 and MoSe2/WSe2 as test cases. In the heterostructure spectra, we observe a significant broadening of the excitonic transitions compared to the corresponding features in the isolated layers. The broadening is interpreted as a lifetime effect arising from decay of excitons initially created in either layer through charge transfer processes expected for a staggered band alignment. The measured spectral broadening of 20 meV - 35 meV implies lifetimes for charge separation of the near band-edge A and B excitons in the range of 20-35 fs. Higher-lying transitions exhibit still greater broadening.
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