Unidirectional Epitaxy of Wafer-Scale MoS2 on Sapphire via Growth Kinetics Control

Abstract

Wafer-scale single-crystalline MoS₂ epitaxially grown on sapphire by chemical vapor deposition (CVD) is expected to exhibit exceptional electrical and optoelectronic properties for the large-scale integration of two-dimensional (2D) semiconductor circuits. Prior studies proposed thermodynamic pathways for achieving unidirectional MoS₂ domains. However, thermodynamic conditions are insufficient to achieve wafer-scale growth of unidirectional MoS₂, while kinetic control during epitaxy remains unexplored. Here, we demonstrate the kinetics-driven adatoms diffusion and nuclei rotation by controlling the epitaxy temperature during the CVD process. We achieve the epitaxy of triangular MoS₂ single-crystalline domains with a single orientation on sapphire. By carefully designing the Mo oxidation, dual-source delivery, and two-stage annealing, the nucleation density of MoS₂ is reduced, and the domain size and uniformity are greatly enhanced. The fine control of the growth kinetics boosts the 2 in. wafer-scale continuous MoS₂ single-crystalline film. The uniformity and single crystallinity were confirmed by Raman spectroscopy, photoluminescence, atomic force microscopy, low-energy electron diffraction, and second-harmonic generation. Furthermore, field-effect MoS₂ transistors exhibited high room-temperature mobility up to 118 cm²·V^–1·s^–1, high on/off ratio over 10¹⁰, and steep subthreshold swing of ∼85 mV·dec^–1. This work not only provides a feasible strategy for the manufacture of high-quality wafer-scale MoS₂ films but also sheds light on the growth of other 2D semiconductor wafers.