Rapid Chloride-Flux Platform for Phase-Selective Growth of Molybdenum Dichalcogenide Single Crystals

Single crystals are important model materials for studying layered metal dichalcogenides (TMDs); however, strategies for phase-selective growth remain limited for the MoX2 (X = S, Se, Te) family. In this study, a rapid (∼48 h) one-step chloride-flux method was developed for the phase-selective growth of MoX2 single crystals and chalcogen-dependent structure–growth relationships governing crystal morphology were established. Single-crystal X-ray diffraction, Raman spectroscopy, and elemental analyses confirmed the crystal structure and composition of the obtained MoX2 single crystals. NaCl–CsCl flux produced 2H-MoS2 single crystals with lateral dimensions of 10–50 μm, whereas NaCl flux yielded 2H-MoSe2 single crystals with lateral dimensions of 5–10 μm. By contrast, MoTe2 crystallized preferentially in the monoclinic 1T′ phase, reflecting its chalcogen-dependent phase stability. Density functional theory calculations revealed pronounced facet-energy anisotropy in MoS2 and MoSe2, which promoted lateral platelet growth, whereas the reduced anisotropy of MoTe2 accounted for its distinct morphology and polymorphism. Furthermore, the flux-grown MoS2 crystals were exfoliated into thin nanosheets. The present chloride-flux growth provides an effective method for the phase-selective synthesis of MoX2 single crystals, and the results of this study offer valuable insights into the crystal growth behavior of layered TMDs.