Defect-Mediated Alloying of Monolayer Transition-Metal Dichalcogenides

Hossein Taghinejad, Daniel A. Rehn, Christine Muccianti, Ali A. Eftekhar, Mengkun Tian, Tianren Fan, Xiang Zhang, Yuze Meng, Yanwen Chen, Tran Vinh Nguyen, Su Fei Shi, Pulickel M. Ajayan, John Schaibley, Evan J. Reed, Ali Adibi

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

Alloying plays a central role in tailoring the material properties of 2D transition-metal dichalcogenides (TMDs). However, despite widespread reports, the details of the alloying mechanism in 2D TMDs have remained largely unknown and are yet to be further explored. Here, we combine a set of systematic experiments with ab initio density functional theory (DFT) calculations to unravel a defect-mediated mechanism for the alloying of monolayer TMD crystals. In our alloying approach, a monolayer MoSe 2 film serves as a host crystal in which exchanging selenium (Se) atoms with sulfur (S) atoms yields a MoS 2x Se 2(1-x) alloy. Our study reveals that the driving force required for the alloying of CVD-grown films with abundant vacancy-type defects is significantly lower than that required for the alloying of exfoliated films with fewer vacancies. Indeed, we show that pre-existing Se vacancies in the host MoSe 2 lattice mediate the replacement of chalcogen atoms and facilitate the synthesis of MoS 2x Se 2(1-x) alloys. Our DFT calculations suggest that S atoms can bind to Se vacancies and then diffuse throughout the host MoSe 2 lattice via exchanging the position with Se vacancies, further supporting our proposed defect-mediated alloying mechanism. Beside native vacancy defects, we show that the existence of large-scale defects in CVD-grown MoSe 2 films causes the fracture of alloys under the alloying-induced strain, while no such effect is observed in exfoliated MoSe 2 films. Our study provides a deep insight into the details of the alloying mechanism and enables the synthesis of 2D alloys with tunable properties.

Original languageEnglish (US)
Pages (from-to)12795-12804
Number of pages10
JournalACS Nano
Volume12
Issue number12
DOIs
StatePublished - Dec 26 2018
Externally publishedYes

Keywords

  • 2D materials
  • alloying
  • defects
  • transition-metal dichalcogenides
  • vacancy

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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