▎ 摘　　要

Upon adsorption onto epitaxial graphene on Ir( 111) at room temperature, Cs adatoms donate part of their charge to the substrate, which effectively creates mutually repelling entities that can diffuse across the graphene surface. By using scanning tunneling microscopy at 6 K, an ordered hexagonal structure of Cs adatoms with several rotated domains has been identified. The amount of charge transferred to graphene has been determined from the presented valence-b band photoemission data. Density-functional calculations show that the repulsive interaction is additionally modulated by preferential adsorption of Cs to the atop region within the moire unit cell. Our results provide direct atomistic insight into the self-assembly of individual atoms on epitaxial graphene, and they demonstrate how the moire structure acts as a perturbation to that process.