Two-dimensional (2D) semiconductors, such as molybdenum disulfide (MoS₂), enable unprecedented opportunities to solve the bottleneck of transistor scaling and to build novel logic circuits with faster speeds, lower power consumption, flexibility and transparency, benefiting from their ultra-thin thickness, dangling-bond-free flat surface and excellent gate controllability.

Tremendous efforts have been devoted to exploring the scaled-up potentials of monolayer MoS₂, including both wafer-scale synthesis of high-quality materials and large-area devices. For instance, four-inch wafer-scale monolayer MoS₂ with large domain sizes (up to ~300 μm) and record-high electronic quality (average field-effect mobility of ~80 cm²·V^-1 ·s^-1) has already been demonstrated via van der Waals epitaxial growth.

In terms of a further improvement of the electronic quality of the large-scale monolayer MoS₂, structural imperfections should be eliminated as much as possible; however, there is not much space left for monolayer MoS₂ after ten years of synthesis optimizations in this field. Another key direction is to switch to multilayer MoS₂, e.g., bilayers and trilayers, since they have intrinsically higher electronic quality than monolayers and thus are conducive to higher-performance devices and logic circuits. However, due to the fundamental limitation of thermodynamics, it is still a great challenge to realize wafer-scale multilayer MoS₂ with high-quality and large-scale uniformity.