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

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 (WO_3−x) precursors and demonstrate the presence of oxygen vacancies in the oxide films leads to a more facile conversion from WO_3−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 WO_3−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.