Growth and in situ characterization of 2D materials by chemical vapour deposition on liquid metal catalysts: a review

2D materials (2DMs) have now been established as unique and attractive alternatives to replace current
technological materials in a number of applications. Chemical vapour deposition (CVD), is undoubtedly
the most renowned technique for thin film synthesis and meets all requirements for automated largescale
production of 2DMs. Currently most CVD methods employ solid metal catalysts (SMCat) for the
growth of 2DMs however their use has been found to induce structural defects such as wrinkles, fissures,
and grain boundaries among others. On the other hand, liquid metal catalysts (LMCat), constitute a possible
alternative for the production of defect-free 2DMs albeit with a small temperature penalty. This
review is a comprehensive report of past attempts to employ LMCat for the production of 2DMs with
emphasis on graphene growth. Special attention is paid to the underlying mechanisms that govern crystal
growth and/or grain consolidation and film coverage. Finally, the advent of online metrology which is particularly
effective for monitoring the chemical processes under LMCat conditions is also reviewed and
certain directions for future development are drawn.