Self-aligned and self-limiting van der Waals epitaxy of monolayer MoS2 to annihilate grain boundaries for scalable 2D electronics

Toward future logic semiconductors at sub-1 nm nodes, unidirectional nucleation followed by seamless stitching has emerged as an exclusive strategy for scalable epitaxial growth of single-crystalline monolayer transition metal dichalcogenides on sapphire substrates. In contrast, here we present a novel growth mechanism for single-crystalline MoS ₂ on c-plane sapphire via metal-organic chemical vapor deposition (MOCVD). The initial nucleation generates not only 0° and antiparallel 60° domains but also low-angle twisted domains, consistent with the coincidence site lattice framework. Nevertheless, these rotationally misoriented domains are deterministically self-aligned and merged into energetically preferred 0° domain during coalescence, yielding a continuous, unidirectional single-crystal. Additionally, by employing MoO ₂ Cl ₂ as a molybdenum precursor, MoS ₂ grows in a self-limiting manner. This epitaxial strategy is substantiated by phonon-limited mobility of 66 cm ² /Vs at room temperature and 749 cm ² /Vs at low temperatures. Our approach offers a practical and reproducible scheme for MOCVD-based van der Waals epitaxy in 2D electronics.