Recent advances in the controlled chemical vapor deposition growth of bilayer 2D single crystals

Abstract

Bilayer two-dimensional (2D) single crystals have attracted intense interest due to their unprecedented properties such as van Hove singularities, superconducting state and tunable bandgap, which are exceptionally greater than those of the existing monolayer 2D materials. Accordingly, the controlled growth of bilayer domains is of great significance, where the chemical vapor deposition (CVD) approach, with the development of techniques, has become the most intuitive and flexible way to achieve this goal. Currently, numerous reports regarding the controllable modulation of the stacking structure and performance of bilayer 2D materials have been published, especially in recent decades; however, a systematic review summarizing and analyzing the state-of-the-art advances in this field is not available. Therefore, herein, we present a summary of the recent research progress on the methods and detailed strategies for the configuration modulation of bilayer 2D materials. Firstly, the general strategies for the synthesis of bilayer graphene domains are provided, highlighting the influence of the substrate, gas flow and growth pressure. Moreover, bilayer transition metal dichalcogenides (TMDs) and hexagonal boron nitride (h-BN) are listed. Thereafter, the growth mechanism of bilayer 2D single crystals is discussed in detail, taking bilayer graphene and bilayer TMD single crystals as examples. Finally, together with the development of bilayer 2D single crystals, the future research challenges towards their controllable growth and high quality and scaled synthesis are outlined, aiming to attract considerable interest in this topic.