More is Better: Epitaxial Multilayer MoS2 Wafers with Promises in High-Performance Transistors

Two-dimensional (2D) semiconductors, such as MoS2, enable the unprecedented possibilities to solve the bottleneck of transistor scaling and to build novel logic circuits with faster speed, lower power consumption, flexibility and transparency, benefiting from their ultra-thin thickness, dangling-bond-free flat surface and excellent gate controllability. In 2015, International Technology Roadmap for Semiconductors (ITRS) clearly pointed out that 2D semiconductors are key materials for next-generation high-performance devices. In 2021, Intel listed 2D MoS2-based transistor technology as one of the three breakthrough technologies for the next decade. Tremendous efforts have been devoted to exploring the scaled-up potentials of monolayer MoS2, including both wafter-scale synthesis of high-quality materials and large-area devices. 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 circuit. 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.