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

Abstract : 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.
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Submitted on : Friday, November 8, 2013 - 3:44:16 PM
Last modification on : Tuesday, November 5, 2019 - 3:16:13 PM
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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⟩

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