Temperature-programmed growth of quasi-free-standing N-doped graphene single crystals from acetonitrile molecules

This paper presents an original technique for temperature-programmed growth of N-doped substrate-sized graphene single crystals on Ni(111). The process includes acetonitrile adsorption at about $-$10$^\circ$ C, flash heating of the sample to 140$^\circ$ C, and annealing at 400$^\circ$ C to form a continuous graphene-structure epitaxial carbon monolayer. The intercalation of gold under the carbon layer on Ni(111) helps create a quasi-free-standing N-doped graphene single crystal. Scanning tunneling microscopy together with density functional theory calculations have been used to determine the structure of nitrogen centers in the graphene. One finding is that nitrogen can be present in the graphene lattice as individual atoms or two- and three-atom clusters. The nitrogen content in graphene can be from 0.2 to 0.6%.