Atomistic simulations of plasma-enhanced chemical vapor deposition of single walled carbon nanotubes

Single walled carbon nanotubes ("SWNTs") are hollow cylindrical structures consisting of a hexagonal carbon network. Their unique properties, such as extreme strength, very high thermal conductivity and structure dependent bandgap, offer perspective on various applications, in e.g. nanoelectronics, as chemical sensors or as induced field emitters. Such applications, however, require precise control over fundamental properties of the SWNTs. This control is currently lacking. Especially control over the chirality of the SWNT, which is directly responsible for the bandbap, is desired. Plasma-enhanced chemical vapor deposition ("PECVD") is regarded as one of the most promising deposition tools to accomplish this control. However, the underlying fundamental growth mechanisms are largely unknown. In this project, we therefore wish to investigate various PECVD-specific processes and process parameters in order to gain insight in the growth mechanisms, aiming at gaining control over the resulting SWNT properties. We wish to accomplish this goal by using a state-of-the-art hybrid Molecular Dynamics / force biased Monte Carlo simulation model, that allows us to simulate self-consistently all relevant processes at the atomic scale. Specifically, we plan (i) to optimize the existing simulation model in order to reduce the required computation time and extend the model to PECVD-growth; (ii) to perform specific simulations to simulate the growth of SWNTs under realistic (PECVD) process conditions on nickel nanocatalysts; (iii) to perform parameter studies that allow us to investigate the effect of the variation of precisely one parameter at a time, in order to determine how we can influence the growth process; and (iv) to develop a force field parametrization for Ni/Fe alloys to be used in the interatomic potential, and subsequent simulation of the PECVD-growth of SWNTs on Ni/Fe nanocatalysts. The innovative character of this project consists of (i) the use of the accurate interatomic potential in combination with the use of the hybrid MD/MC model that takes into account both short time scale as well as long time scale events; (ii) the study of SWNT growth in a PECVD-setup by means of atomistic simulations; and (iii) de development and application of Ni/Fe force field parameters for the simulation of PECVD-growth of SWNTs on Ni/Fe nanocatalysts. Although this project is indeed very innovative (both regarding the used methodology as the goals we are aiming for), we believe that this project is very feasible: indeed, we have already proven the effectivity of the simulation model in simulating the growth of SWNTs under thermal CVD conditions. Furthermore, we have access to all required tools needed to simulate the PECVD-specific process conditions. We therefore believe that we will be able to unravel fundamental processes in PECVD growth of SWNTs and to gain insight in this promising but until now at the atomic level nearly unexplored process.

Keywords:PLASMA ENHANCED CHEMICAL VAPOR DEPOSITION, COMPUTER SIMULATIONS, CARBON NANOTUBES, CHIRALITY

Disciplines:Condensed matter physics and nanophysics, Physical chemistry