Effect of Substrate Miscut on the Epitaxial Growth of MoS2 on Sapphire.

The combined effects of substrate miscut angle and growth temperature on the epitaxial growth and properties of MoS2 monolayers synthesized by metalorganic chemical vapor deposition (MOCVD) on c-plane sapphire substrates were investigated. Increasing the miscut angle toward the M-axis produces faceted step-terrace surfaces with higher step density and reduced terrace width on the sapphire surface, while promoting pronounced step bunching during growth. These miscut-induced surface reconstructions strongly modulate MoS2 growth, leading to systematic changes in bilayer domain density, size, morphology, and epitaxial alignment without significantly altering the growth rate. Comprehensive structural, optical, and electronic characterizations reveal that growth at 1000 °C on the lowest miscut (0.2°) sapphire yields the highest quality monolayer MoS2, as evidenced by the low full width at half-maximum of the in-plane X-ray diffraction φ-scan peaks, minimized defect-bound exciton emission in photoluminescence spectra at cryogenic temperatures, and superior field-effect transistor performance. In contrast, 1° miscut substrates promote increased bilayer domain density, likely due to increased step bunching of the sapphire, making them suitable for controlled bilayer MoS2 growth. However, further increasing the miscut to 4° or lowering the growth temperature to 950 °C results in significantly degraded structural, optical, and electrical properties. These results highlight the importance of substrate miscut and its role in governing the epitaxial growth of MoS2, offering valuable guidance for the scalable synthesis of high-quality two-dimensional MoS2 films.