液态金属催化剂:二维材料的点金石

摘要

Graphene and graphene-like two-dimensional (2D) materials exhibit broad prospects for application in emerging electronics owing to their unique structure and excellent properties.However,there are still many challenges facing the achievement of controllable growth,which is the main bottleneck that limits the practical application of these materials.Chemical vapor deposition (CVD) is the most effective method for the controllable growth of high-quality graphene,in which the design of the catalytic substrate catches the most attention because it directly determines the two most significant basal processes——catalyzation and mass transfer.Recently,compared with the selection of the chemical composition of the catalyst,the change of the physical state of the catalyst from a solid phase to liquid phase is expected to lead to a qualitative change and improvement in the CVD of graphene and graphene-like two-dimensional materials.Unlike solid substrates,liquid substrates exhibit a loose atomic arrangement and intense atom movement,which contribute to a smooth and isotropic liquid surface and a fluidic liquid phase that can embed heteroatoms.Therefore,liquid metal shows many unique behaviors during the catalyzation of the growth of graphene,graphene-like two dimensional materials,and their heterostructures,such as stdct self-limitation,ultra-fast growth,and smooth stitching of grains.More importantly,the rheological properties of a liquid substrate can even facilitate the self-assembly and transfer of 2D materials grown on it,in which the liquid metal substrate can be regarded as the ‘philosopher's stone’.This feature article summarizes the growth,assembly,and transfer behavior of 2D materials on liquid metal catalysts.These primary technology developments will establish a solid foundation for the practical application of 2D materials.%由于石墨烯等二维材料具有独特的结构与优异的性能,其在众多新型电子器件的构建中具有重要的应用前景.然而,其可控生长仍然存在诸多挑战性的问题,这也是制约这类明星材料真正迈向应用的瓶颈所在.化学气相沉积法(CVD)是目前可控制备高质量石墨烯最有效的方法,其中催化基底的设计尤为重要,这将直接决定CVD最为核心的两个过程:催化和传质.相较于改变催化剂的化学组成,近年来我们发现改变催化剂的物态——由固态到液态,对石墨烯等二维材料的CVD过程有质的改变和提升.与固态基底相比,液态基底具有更松散的原子排列、更剧烈的原子迁移,使得液面平滑而各向同性,液相可流动且可包埋异质原子.这使得液态金属在催化石墨烯等二维材料及其异质结生长时表现出很多独特的行为,比如层数严格自限制、超快的生长速度、晶粒拼接平滑等.更重要的是,基底的液态特性给二维材料的自组装和转移带来了突破,实乃二维材料的点金石.本文将梳理液态金属催化剂上二维材料的生长、组装与转移行为,这些关键技术的突破将为二维材料迈向真正应用奠定坚实的基础.