Capillary Wave Driven Dynamics of Graphene Domains during Growth on Molten Metals

Rheotaxy─growth of crystalline layers on molten surfaces─is considered as a promising approach for achieving large-scale monolayers of two-dimensional (2D) materials via seamless stitching of 2D domains during growth on molten metals. However, the mechanisms leading to this process are not well understood. Here, we present in situ microscopic observations of rheotaxy of graphene via chemical vapor deposition on molten gold and copper. We show that the graphene domains undergo translational and rotational motions, leading to self-assembly, during growth on molten metals. Using environmental and ultrahigh vacuum scanning electron microscopy and high-temperature (∼1300 K) atomic force microscopy, coupled with density functional theory and continuum modeling, we suggest that the observed graphene domain dynamics is due to forces arising from capillary waves on the surface of the liquid metal. Our results provide new insights into the mechanisms leading to self-assembly during rheotaxy of 2D layers.