Synthesis of High-Quality WS₂ Crystals on an Ionic Liquid Surface Near Room Temperature

High-quality and catalyst-free fabrication of transition-metal dichalcogenides at room temperature has been a goal in the two-dimensional material research field. In this work, we report an efficient approach to synthesize high-quality tungsten disulfide (WS2) via an optimized low-pressure chemical vapor deposition (LP-CVD) technique on an ionic liquid surface near room temperature. It is found that single- to few-layered and bulk-shaped (triangular and hexagonal) WS2 crystals may be prepared on the liquid surface simultaneously. The most probable sizes of the triangular and hexagonal WS2 crystals are 574.7 ± 18.4 and 399.3 ± 41.0 nm, respectively. The average terrace width of the WS2 crystals with multiple concentric hexagons is about 35 nm. Based on the experimental results, a three-stage growth model of the WS2 crystals is proposed. The work provides an understanding of the mechanism of the crystals and shows an optimization of the growth process on the liquid substrates.