Thermodynamic analysis of graphene CVD grown on liquid metal: Growth on liquid metallic gallium or solid gallium oxide skin?

A number of recent publications have reported liquid gallium to have an extraordinary catalytic activity for chemical vapor deposition (CVD) of graphene, enabling the growth of high-quality graphene on its surface even below 600 K. Our presented thermodynamic analysis however, indicates that during several of these experiments, an atomically thin gallium oxide layer should have covered the liquid gallium. This means that graphene should have actually grown on the solid oxide skin rather than on the liquid metal. This suggests a more complex mechanism for graphene growth on liquid gallium than what is currently considered in the community.