Droplet-Mediated Vapor–Liquid–Solid Growth of Pyramidal MoS2 via the Supersaturation-Governed Transition from Lateral Growth to Vertical Stacking

Three-dimensional MoS 2 structures provide enriched interlayer coupling, abundant edge/step sites, and thickness gradients, opening opportunities for tailoring electronic and interfacial functionalities. Controlled growth of pyramidal MoS 2 remains challenging because its structure is governed by precursor supply, local supersaturation, and secondary nucleation. Herein, we report a droplet-mediated vapor–liquid–solid CVD strategy for the controllable growth of pyramidal MoS 2 using precursor-rich Na–Mo–O droplets as localized precursor reservoirs and reaction interfaces. Statistical analysis reveals a correlation between droplet diameter and pyramid lateral size, indicating the strong coupling between droplet-mediated supply and crystal growth. Combined classical nucleation theory and DFT calculations support a supersaturation-governed growth transition. Under low effective interfacial supersaturation, upper-step nucleation is less accessible and lateral growth is favored, whereas increasing effective interfacial supersaturation progressively facilitates secondary nucleation and step stacking. KPFM further reveals a stepwise evolution of surface potential along the thickness gradient. Despite the microscale channel thickness and interlayer screening, back-gated transistors based on pyramidal MoS 2 remain electrically addressable, exhibiting apparent two-terminal field-effect mobilities of 4–6 cm 2 V –1 s –1 and on/off ratios on the order of 10 3 . This work establishes a controllable route to thickness-graded three-dimensional MoS 2 structures and provides mechanistic insight into stacking growth in layered semiconductors.