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Title: Accelerated carrier recombination by grain boundary/edge defects in MBE grown transition metal dichalcogenides

Abstract

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 MoTe 2 and MoSe 2. 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 MoTe 2, 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.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [2];  [1];  [3];  [2];  [3]
  1. Univ. of Texas, Austin, TX (United States). Dept. of Mechanical Engineering
  2. Univ. of Texas, Austin, TX (United States). Microelectronics Research Center and Dept. of Electrical and Computer Engineering
  3. Univ. of Texas, Austin, TX (United States). Dept. of Mechanical Engineering, and Texas Materials Inst.
Publication Date:
Research Org.:
Omega Optics, Inc., Austin, TX (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1501520
Alternate Identifier(s):
OSTI ID: 1436017
Grant/Contract Number:  
SC0013178
Resource Type:
Accepted Manuscript
Journal Name:
APL Materials
Additional Journal Information:
Journal Volume: 6; Journal Issue: 5; Journal ID: ISSN 2166-532X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Chen, Ke, Roy, Anupam, Rai, Amritesh, Movva, Hema C. P., Meng, Xianghai, He, Feng, Banerjee, Sanjay K., and Wang, Yaguo. Accelerated carrier recombination by grain boundary/edge defects in MBE grown transition metal dichalcogenides. United States: N. p., 2018. Web. doi:10.1063/1.5022339.
Chen, Ke, Roy, Anupam, Rai, Amritesh, Movva, Hema C. P., Meng, Xianghai, He, Feng, Banerjee, Sanjay K., & Wang, Yaguo. Accelerated carrier recombination by grain boundary/edge defects in MBE grown transition metal dichalcogenides. United States. doi:10.1063/1.5022339.
Chen, Ke, Roy, Anupam, Rai, Amritesh, Movva, Hema C. P., Meng, Xianghai, He, Feng, Banerjee, Sanjay K., and Wang, Yaguo. Fri . "Accelerated carrier recombination by grain boundary/edge defects in MBE grown transition metal dichalcogenides". United States. doi:10.1063/1.5022339. https://www.osti.gov/servlets/purl/1501520.
@article{osti_1501520,
title = {Accelerated carrier recombination by grain boundary/edge defects in MBE grown transition metal dichalcogenides},
author = {Chen, Ke and Roy, Anupam and Rai, Amritesh and Movva, Hema C. P. and Meng, Xianghai and He, Feng and Banerjee, Sanjay K. and Wang, Yaguo},
abstractNote = {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.},
doi = {10.1063/1.5022339},
journal = {APL Materials},
number = 5,
volume = 6,
place = {United States},
year = {2018},
month = {5}
}

Journal Article:
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Cited by: 3 works
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Figures / Tables:

FIG. 1. FIG. 1. : [(a) and (b)] TEM images of MBE-grown MoTe2 and MoSe2.10 Abundent nano-sized grains and plenty of grain boundary/edge defects are present. The arrows indicate some of the grain boundaries and edges. Reprinted with permission from Roy et al., ACS Appl. Mater. Interfaces 8(11), 7396–7402 (2016). Copyright 2016more » American Chemical Society. (c) TEM images of exfoliated MoSe2.14 Very few grain boundary/edge defects can be seen. The arrows indicate the border of the exfoliated sheet. Reprinted with permission from Lei et al., Small 12(23), 3112–3118 (2016). Copyright 2016 John Wiley & Sons, Inc.« less

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