A facile strategy for the growth of high-quality tungsten disulfide crystals mediated by oxygen-deficient oxide precursors

Denys I. Miakota, Raymond R. Unocic, Fabian Bertoldo, Ganesh Ghimire, Sara Engberg, David Geohegan, Kristian S. Thygesen, Stela Canulescu*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Chemical vapor deposition (CVD) has been established as a versatile route for the large-scale synthesis of transition metal dichalcogenides, such as tungsten disulfide (WS2). Yet, the precursor composition's role on the CVD process remains largely unknown and remains to be explored. Here, we employ Pulsed Laser Deposition (PLD) in a two-stage approach to tune the oxygen content in the tungsten oxide (WO3−x) precursors and demonstrate the presence of oxygen vacancies in the oxide films leads to a more facile conversion from WO3−x to WS2. Using a joint study based on ab initio density functional theory (DFT) calculations and experimental observations, we unravel that the oxygen vacancies in WO3−x can serve as niches through which sulfur atoms enter the lattice and facilitate an efficient conversion into WS2 crystals. By solely modulating the precursor stoichiometry, the photoluminescence emission of WS2 crystals can be significantly enhanced. Atomic resolution scanning transmission electron microscopy imaging (STEM) reveals that tungsten vacancies are the dominant intrinsic defects in mono- and bilayers WS2. Moreover, bi- and multilayer WS2 crystals derived from oxides with a high V0 content exhibit dominant AA′/AB or AA(A…) stacking orientations. The atomic resolution images reveal local strain buildup in bilayer WS2 due to competing effects of complex grain boundaries. Our study provides means to tune the precursor composition to control the lateral growth of TMDs while revealing insights into the different pathways for forming grain boundaries in bilayer WS2

Original languageEnglish
JournalNanoscale
Volume14
Issue number26
Pages (from-to)9485-9497
ISSN2040-3364
DOIs
Publication statusPublished - 24 Jun 2022

Keywords

  • Transition-metal dichalcogenides
  • WS2 monolayers
  • Pulsed laser deposition (PLD),
  • Chemical vapor deposition (CVD)
  • Epitaxial oxides

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