Towards the fundamental research and device applications of two-dimensional (2D) materials, hexagonal boron nitride (h-BN) is the ideal dielectric substrate and encapsulating layer due to its atomic flat surface and the absence of dangling bonds on the surface. Compared with monolayer h-BN, high-quality multilayer h-BN plays a key role in maintaining the intrinsic properties of 2D atomic crystals. However, the low thickness control and high crystallinity of h-BN films are still issues that remain elusive.
In this study, Wu group in Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences, report a vapor–liquid–solid growth method to achieve uniform multilayer h-BN by using a molten Fe82B18 alloy and N2 as reactants. The molten Fe82B18 not only supplies boron but also continuously dissociates N atoms from the N2 vapor. Sufficient vacancies in liquid alloy and the orientation relationship between sapphire substrate and h-BN promote the controllable growth of large-area h-BN films with a thickness of 5-50 nm on sapphire substrate (see in Fig.1). The new growth strategy developed here has certain pioneering significance for the large-scale fabrication of 2D binary atomic crystals.
Fig. 1 | Vapor–liquid–solid growth of large-area multilayer h-BN on dielectric substrates
Wang group in SIMIT further verified that the CVD-grown multilayer h-BN can effectively maintain the intrinsic properties of 2D atomic crystals. Liu group at the School of Material Science and Technology of ShanghaiTech University used in situ near-ambient pressure XPS to observe how the B-N associates initially formed and understand the associated segregation mechanism. The approach exhibited potential for large-area synthesis of multilayer h-BN and integration of other two-dimensional materials.
For more details, please read the paper " Vapor–Liquid–Solid Growth of Large-area Multilayer Hexagonal Boron Nitride on Dielectric Substrates" published in Nature Communications (https://www.nature.com/articles/s41467-020-14596-3). Dr. Zhiyuan Shi and Miss. Xiujun Wang in SIMIT contributed equally to this work. Associate professor Dr. Tianru Wu and professor Dr. Haomin Wang in SIMIT are co-corresponding authors.
This work is supported by the National Natural Science Foundation of China, the Strategic Priority Research Program of Chinese Academy of Sciences, the Science and Technology Commission of Shanghai Municipality, Youth Innovation Promotion Association of Chinese Academy of Sciences and Shanghai Rising-Star Program (A type).