About the step-flow mechanism at the origin of graphene crystallisation at the surface of catalysts

Jean-Luc Maurice (1) , Didier Pribat (2) , Zhanbing He (3, 1) , Gilles Patriarche (4) , Costel Sorin Cojocaru (1)

1 LPICM - Laboratoire de physique des interfaces et des couches minces [Palaiseau]
2 Department of Energy Science
3 State Key Laboratory for Advanced Metals and Materials
4 LPN - Laboratoire de photonique et de nanostructures

The nucleation and growth of multiwall carbon nanotubes (MWCNTs) at the surface of crystalline iron-based catalysts are studied by in situ annealing and high-resolution transmission electron microscopy. Graphene planes, parallel to the catalyst surface, appear by a mechanism of step flow, where the atomic layers of catalyst are "replaced" by graphene layers. More interestingly, as the catalyst particles have curved or poly-faceted surfaces, those catalyst atomic layers correspond to no definite atomic plane. The step height may thus vary along a given step flow process. Step bunching due to impeded step migration, in certain growth conditions, yields characteristic catalyst nail-head shapes. Mastering this mechanism opens up the way to tailor the structure of MWCNTs, e.g. with highly parallel carbon walls.

Keywords: graphene; multiwall carbon nanotubes; catalyst assisted chemical vapour deposition; C-CVD; in-situ transmission electron microscopy; in-situ TEM

Domains: Physics [physics]; Condensed Matter [cond-mat]; Materials Science [cond-mat.mtrl-sci]

Jean-Luc Maurice, Didier Pribat, Zhanbing He, Gilles Patriarche, Costel Sorin Cojocaru. About the step-flow mechanism at the origin of graphene crystallisation at the surface of catalysts. 2013. ⟨hal-00880670⟩