Homogeneous nucleation of graphitic nanostructures from carbon chains on Ni(111)

The structure, energetics, and mobility of carbon aggregates up to 10 atoms on the Ni(111) surface are investigated via first-principles simulations. Chain configurations are predicted to be thermodynamically favored over rings and present a high mobility (with long chains diffusing even faster than adatoms), whereas branched configurations are much less mobile but kinetically robust, as they present substantial energy barriers for interconversion into other species. A model of growth via homogeneous nucleation is proposed in which incoming C atoms generate chains which diffuse rapidly and collect less mobile adatoms in their channels until they meet in an unfavorable configuration and start networking giving rise to starlike branching points, which are homologous to graphene and act as the nuclei of growth. It is argued that the proposed homogeneous nucleation mechanism should be observed experimentally, especially in mild conditions and on low-defect Ni(111) surfaces.