title: Early stages in the nucleation process of carbon nanotubes.
abstract: The early stages of carbon nanotube nucleation are investigated using field ion/electron microscopy along with in situ local chemical probing of a single nanosized nickel crystal. To go beyond experiments, tight-binding Monte Carlo simulations are performed on oriented Ni slabs. Real-time field electron imaging demonstrates a carbon-induced increase of the number density of steps in the truncated vertices of a polyhedral Ni nanoparticle. The necessary diffusion and step-site trapping of adsorbed carbon atoms are observed in the simulations and precede the nucleation of graphene-based sheets in these steps. Chemical probing of selected nanofacets of the Ni crystal reveals the occurrence of Cn (n=1-4) surface species. Kinetic studies prove C2+ species are formed from C1 with a delay time of several milliseconds at 623 K. Carbon dimers, C2, must not necessarily be formed on the Ni surface. Tight-binding Monte Carlo simulations reveal the high stability of such dimers in the first layer beneath the surface.
authors.affiliation: Chemical Physics of Materials, Faculté des Sciences, Université Libre de Bruxelles, Bruxelles, Belgium.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Moors
authors.forename: Hakim
authors.initials: H
authors.lastname: Amara
authors.forename: Thierry Visart
authors.initials: TV
authors.lastname: de Bocarmé
authors.forename: Christophe
authors.initials: C
authors.lastname: Bichara
authors.forename: François
authors.initials: F
authors.lastname: Ducastelle
authors.forename: Norbert
authors.initials: N
authors.lastname: Kruse
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Charlier