Single Atoms as Growth Directors: From Graphene Edges to Atomically Precise Interfaces in 2D Materials

Single-atom catalysts are often framed as isolated reactive sites that maximize atom efficiency in chemical transformations. A less explored role is their function as growth directors, viz., atomic-scale agents that bias nucleation pathways, steer incorporation events, and shape early-stage morphologies with precision beyond that of nanoparticles. The strongest experimental evidence comes from graphene, where advanced scanning tunneling and scanning/transmission electron microscopies enable direct tracking of atoms at growth edges and kinks, linking configurations to stepwise growth. First-principles studies on Rh(111) propose that transition-metal single atoms, particularly Mo, can promote productive feeding species such as diatomic carbon and boron nitride (BN) dimers, lower kinetic barriers during early h-BN-graphene lateral heterostructure growth, and influence boundary chemistry. This perspective reframes single atoms as growth directors, distills the mechanistic insights established for graphene, extends them to emerging heterostructures, and outlines criteria for identifying single-atom-directed growth, providing a basis for the rational design of atomically precise 2D interfaces.