Early stages in the nucleation process of carbon nanotubes.
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.
Moors
Matthieu
M
Chemical Physics of Materials, Faculté des Sciences, Université Libre de Bruxelles, Bruxelles, Belgium.
Amara
Hakim
H
de Bocarmé
Thierry Visart
TV
Bichara
Christophe
C
Ducastelle
François
F
Kruse
Norbert
N
Charlier
Jean-Christophe
JC