Christophe Bichara

Abstract:

The outstanding physical properties of novel carbon-based materials (nanotubes, graphene) strongly depend on their structure: chirality for single wall carbon nanotubes (SWNT), number of layers and stacking for graphene. However, materials produced are far from being ideal and a detailed atomic scale understanding of the nucleation and growth of SWNT and graphene, as provided by computer simulation, is still highly desirable. In this presentation, I will first introduce the field and discuss some key issues relevant to the controlled Chemical Vapor Deposition synthesis of SWNTs and Graphene on a metal catalyst. I will show how various computer simulation techniques, from DFT based calculations to Monte Carlo or Molecular Dynamics simulations based on more empirical models, lead to a better understanding of the processes involved. I will then focus on our approach, based on a tight binding model for nickel and carbon implemented in Grand Canonical Monte Carlo simulations, to numerically investigate different aspects of the CCVD synthesis. We first study the chemical and physical states of the metal catalyst as a function of size, temperature and carbon chemical potential conditions corresponding to nucleation and growth of SWNTs and graphene. We then show how the growth modes of carbon nanotubes that have been identified experimentally critically depend on metal/carbon interfacial properties that are directly controlled by carbon solubility. This leads to an understanding of different growth regimes, and ultimately should provide routes to the chirality selective synthesis of SWNT that is the remaining challenge, pioneered by a number experimental groups.