Chemical vapor deposition growth of 2-dimensional materials on liquid metal catalysts: Analyzing the thermodynamic and kinetic phenomena at play

Since the first isolation of graphene in 2004, a whole range of two-dimensional (2D) materials have been discovered, offering diverse electronic properties that are relevant to applications in, e.g., nanoelectronics, catalysis, or sensing. A major bottleneck that remains to this day is the controlled large-scale production of single-crystalline monolayers without significant defect density. In the last decade, it has been demonstrated that 2D materials can be grown by chemical vapor deposition (CVD) methods on liquid metals as a substrate. Liquid metals, not being constrained to a specific surface crystallography, allow to grow large, single-crystalline monolayers of various materials such as graphene, hexagonal boron nitride, and MXenes. While large progress has been achieved in the field, deeper insights into fundamental growth mechanisms are required in order to provide a solid understanding of the underlying chemistry. In this review, we lay the theoretical framework of nucleation and growth of nanomaterials, specifically 2D materials, and their growth by CVD on liquid metals. We review the growth mechanisms of major classes of 2D materials, as well as draw a picture of the thermodynamic and kinetic parameters at play. In the last part, tools for experimental studies of the growth of 2D materials by CVD on liquid metals are discussed. This review aims at harnessing the key concepts one might need to thoroughly analyze the outcome of one of these synthesis procedures, as well as providing insights in the development of the techniques in an effort of synthesizing 2D materials at a large scale.