A comparative study of intercalation mechanism at graphene/Ru(0001) interface

Both Ni and Pb intercalation reactions at graphene/Ru(0001) interface were studied by low energy electron microscopy (LEEM) and photoemission electron microscopy (PEEM). It is suggested that the Ni intercalation is dominated by an exchange intercalation mechanism, in which Ni adatoms produce transient atomic-scale defects in the graphene lattice and penetrate through the carbon monolayer. In contrast, the Pb intercalation process needs to be facilitated by the diffusion of Pb atoms through extended defect sites of graphene, such as open edges and domain boundaries. The two contrast intercalation mechanisms originate from the different interaction strength of the intercalated elements with carbon. Different responses of the graphene electronic structure to the Ni and Pb intercalation reactions were observed by PEEM.