The effect of vortex suppression on the large-scale epitaxial growth of unidirectional MoS₂

The scalable synthesis of high-quality, single-crystalline two-dimensional molybdenum disulfide (MoS₂) by chemical vapor deposition (CVD) is primarily hindered by inhomogeneous precursor delivery and non-uniform nucleation. While the “face-to-face” configuration improves precursor uniformity, its scalability to wafer-scale is limited by vortex formation. Herein, we introduce an open-ended boat design that fundamentally eliminates vortex and establishes a stable gas flow over the 1.5-inch sapphire substrate. Through full-reactor computational fluid dynamics (CFD) simulations and experimental validation, we precisely identify and resolve the vortex issue, demonstrating that our design ensures a uniform and sufficient supply of both Mo and S precursors across the entire substrate. This optimized flow environment not only facilitates epitaxial alignment via step-edge guidance on sapphire but also enables the expansion of large, well-oriented domains. As a result, highly uniform, unidirectional MoS₂ quasi-single-crystals were achieved on 1.5-inch wafer-scale sapphire substrates. This study elucidates the crucial role of fluid dynamics in 2D material growth, effectively addressing the scalability challenge in conventional CVD processes.