Journal
APL MATERIALS
Volume 6, Issue 5, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.5022339
Keywords
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Funding
- National Science Foundation (NASCENT) [EEC-1160494]
- National Science Foundation [CBET-1351881]
- Department of Energy (SBIR/STTR) [DE-SC0013178]
- DOD Army [W911NF-16-1-0559]
- MURI Grant [W911NF-17-1-0312]
- U.S. Department of Energy (DOE) [DE-SC0013178] Funding Source: U.S. Department of Energy (DOE)
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Defect-carrier interaction in transition metal dichalcogenides (TMDs) plays important roles in carrier relaxation dynamics and carrier transport, which determines the performance of electronic devices. With femtosecond laser time-resolved spectroscopy, we investigated the effect of grain boundary/edge defects on the ultrafast dynamics of photoexcited carrier in molecular beam epitaxy (MBE)-grown MoTe2 and MoSe2. We found that, comparing with exfoliated samples, the carrier recombination rate in MBE-grown samples accelerates by about 50 times. We attribute this striking difference to the existence of abundant grain boundary/edge defects in MBE-grown samples, which can serve as effective recombination centers for the photoexcited carriers. We also observed coherent acoustic phonons in both exfoliated and MBE-grown MoTe2, indicating strong electron-phonon coupling in this materials. Our measured sound velocity agrees well with the previously reported result of theoretical calculation. Our findings provide a useful reference for the fundamental parameters: carrier lifetime and sound velocity and reveal the undiscovered carrier recombination effect of grain boundary/edge defects, both of which will facilitate the defect engineering in TMD materials for high speed opto-electronics. (C) 2018 Author(s).
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