Size-Selective Carbon Nanoclusters as Precursors to the Growth of Epitaxial Graphene

• Published in: Nano letters 2011-02, Vol.11 (2), p.424-430
• Main Authors: Wang, Bo, Ma, Xiufang, Caffio, Marco, Schaub, Renald, Li, Wei-Xue
• Format: Article
• Language: English
• Subjects: Computer Simulation; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crystallization - methods; Electron states; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; General studies of phase transitions; Graphite - chemistry; Macromolecular Substances - chemistry; Materials science; Materials Testing; Methods of electronic structure calculations; Models, Chemical; Models, Molecular; Molecular Conformation; Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals; Nanotechnology - methods; Nanotubes, Carbon - chemistry; Nanotubes, Carbon - ultrastructure; Nucleation; Particle Size; Physics; Specific materials; Structure of solids and liquids; crystallography; Surface Properties
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl103053t

The nucleation and growth mechanisms of graphene on Rh(111) via temperature-programmed growth of C2H4 are studied by scanning tunneling microscopy and spectroscopy, and by density functional theory calculations. By combining our experimental and first-principles approaches, we show that carbon nanoislands form in the initial stages of graphene growth, possessing an exclusive size of seven honeycomb carbon units (hereafter labeled as 7C6). These clusters adopt a domelike hexagonal shape indicating that bonding to the substrate is localized on the peripheral C atoms. Smoluchowski ripening is identified as the dominant mechanism leading to the formation of graphene, with the size-selective carbon islands as precursors. Control experiments and calculations, whereby coronene molecules, the hydrogenated analogues of 7C6, are deposited on Rh(111), provide an unambiguous structural and chemical identification of the 7C6 building blocks.