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Title: Direct Cation Exchange in Monolayer MoS 2 via Recombination-Enhanced Migration

Abstract

In addition to their unique optical and electronic properties, two-dimensional materials provide opportunities to directly observe atomic-scale defect dynamics. Here we use scanning transmission electron microscopy to observe substitutional Re impurities in monolayer MoS 2 undergo direct exchanges with neighboring Mo atoms in the lattice. Density-functional-theory calculations find that the energy barrier for direct exchange, a process that has only been studied as a diffusion mechanism in bulk materials, is too large for either thermal activation or energy directly transferred from the electron beam. The presence of multiple sulfur vacancies next to the exchanged Re-Mo pair, as observed by electron microscopy, does not lower the energy barrier sufficiently to account for the observed atomic exchange. Instead, the calculations find that a Re dopant and surrounding sulfur vacancies introduce an ever-changing set of deep levels in the energy gap. We propose that these levels mediate an “explosive” recombination-enhanced migration via multiple electron-hole recombination events. As a proof of concept, we also show that Re-Mo direct exchange can be triggered via controlled creation of sulfur vacancies. The present experimental and theoretical findings lay a fundamental framework towards manipulating single substitutional dopants in two-dimensional materials.

Authors:
 [1];  [2];  [3];  [4];  [1];  [1];  [5];  [1];  [3];  [6]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Vanderbilt Univ., Nashville, TN (United States)
  3. Vanderbilt Univ., Nashville, TN (United States); Chinese Academy of Sciences (CAS), Beijing (China)
  4. Beihang Univ., Beijing (China)
  5. Rice Univ., Houston, TX (United States)
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chinese Academy of Sciences (CAS), Beijing (China)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1502522
Alternate Identifier(s):
OSTI ID: 1546392
Grant/Contract Number:  
AC05-00OR22725; FG02-09ER46554; AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 122; Journal Issue: 10; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Yang, Shi-Ze, Sun, Weiwei, Zhang, Yu-Yang, Gong, Yongji, Oxley, Mark P., Lupini, Andrew R., Ajayan, Pulickel M., Chisholm, Matthew F., Pantelides, Sokrates T., and Zhou, Wu. Direct Cation Exchange in Monolayer MoS2 via Recombination-Enhanced Migration. United States: N. p., 2019. Web. doi:10.1103/PhysRevLett.122.106101.
Yang, Shi-Ze, Sun, Weiwei, Zhang, Yu-Yang, Gong, Yongji, Oxley, Mark P., Lupini, Andrew R., Ajayan, Pulickel M., Chisholm, Matthew F., Pantelides, Sokrates T., & Zhou, Wu. Direct Cation Exchange in Monolayer MoS2 via Recombination-Enhanced Migration. United States. doi:10.1103/PhysRevLett.122.106101.
Yang, Shi-Ze, Sun, Weiwei, Zhang, Yu-Yang, Gong, Yongji, Oxley, Mark P., Lupini, Andrew R., Ajayan, Pulickel M., Chisholm, Matthew F., Pantelides, Sokrates T., and Zhou, Wu. Mon . "Direct Cation Exchange in Monolayer MoS2 via Recombination-Enhanced Migration". United States. doi:10.1103/PhysRevLett.122.106101.
@article{osti_1502522,
title = {Direct Cation Exchange in Monolayer MoS2 via Recombination-Enhanced Migration},
author = {Yang, Shi-Ze and Sun, Weiwei and Zhang, Yu-Yang and Gong, Yongji and Oxley, Mark P. and Lupini, Andrew R. and Ajayan, Pulickel M. and Chisholm, Matthew F. and Pantelides, Sokrates T. and Zhou, Wu},
abstractNote = {In addition to their unique optical and electronic properties, two-dimensional materials provide opportunities to directly observe atomic-scale defect dynamics. Here we use scanning transmission electron microscopy to observe substitutional Re impurities in monolayer MoS2 undergo direct exchanges with neighboring Mo atoms in the lattice. Density-functional-theory calculations find that the energy barrier for direct exchange, a process that has only been studied as a diffusion mechanism in bulk materials, is too large for either thermal activation or energy directly transferred from the electron beam. The presence of multiple sulfur vacancies next to the exchanged Re-Mo pair, as observed by electron microscopy, does not lower the energy barrier sufficiently to account for the observed atomic exchange. Instead, the calculations find that a Re dopant and surrounding sulfur vacancies introduce an ever-changing set of deep levels in the energy gap. We propose that these levels mediate an “explosive” recombination-enhanced migration via multiple electron-hole recombination events. As a proof of concept, we also show that Re-Mo direct exchange can be triggered via controlled creation of sulfur vacancies. The present experimental and theoretical findings lay a fundamental framework towards manipulating single substitutional dopants in two-dimensional materials.},
doi = {10.1103/PhysRevLett.122.106101},
journal = {Physical Review Letters},
number = 10,
volume = 122,
place = {United States},
year = {2019},
month = {3}
}

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