Growth of sp-sp2 nanostructures in a carbon plasma

The growth of sp and sp2 nanostructures in a carbon plasma is simulated by tight-binding molecular dynamics. The simulations are arranged so as to mimic the cluster formation conditions typical of a pulsed microplasma cluster source which is used to grow nanostructured sp-sp2 carbon films [L. Ravagnan et al., Phys. Rev. Lett. 98, 216103 (2007)]. The formation of linear, ring, and fullerenelike objects in the carbon plasma is found to proceed through a very long multistep process. Therefore, tight-binding simulations of unprecedented duration have been performed by exploiting the disconnected topology of the simulated carbon plasma which made it possible to implement a computationally efficient divide-and-diagonalize procedure. Present simulations prove that topologically different structures can be formed in experiments, depending on the plasma temperature and density. A thorough characterization of the observed structures as well as their evolution (caused both by thermal annealing and by cluster ripening) is provided.