Self-assembly mechanisms of short atomic chains on single-layer graphene and boron nitride

Abstract

Nucleation and growth mechanisms of short chains of carbon atoms on single-layer, hexagonal boron nitride (h-BN) and short BN chains on graphene are investigated using first-principles plane-wave calculations. Our analysis starts with the adsorption of a single carbon adatom and examines its migrations. Once a C-2 nucleates on h-BN, the insertion of each additional carbon at its close proximity causes a short segment of carbon atomic chain to grow by one atom at at a time in a quaint way: The existing chain leaves its initial position and subsequently is attached from its bottom end to the top of the carbon adatom. The electronic, magnetic, and structural properties of these chains vertically adsorbed to h-BN depend on the number of carbon atoms in the chain, such that they exhibit an even-odd disparity. An individual carbon chain can also modify the electronic structure with localized states in the wide band gap of h-BN. As a reverse situation, we examined the growth of short BN atomic chains on graphene, which attribute diverse properties depending on whether B or N is the atom bound to the substrate. These results together with ab initio molecular dynamics simulations of the growth process reveal the interesting self-assembly behavior of the grown chains. Furthermore, we find that these atomic chains enhance the chemical activity of h-BN and graphene sheets by creating active sites for the bonding of various adatoms and can act as pillars between two and multiple sheets of these honeycomb structures, leaving wider spacing between them to achieve high-capacity storage of specific molecules.