Growth Analysis of Single-Walled Carbon Nanotubes Based on Interatomic Potentials by Molecular Dynamics Simulation

Molecular dynamics simulation was performed to understand the growth mechanism of single-walled carbon nanotubes (SWNTs) by using the Brenner–Tersoff potential as the interaction among carbon atoms (C–C) and the Tersoff-type potential as the interaction between carbon and metal (C–M) and between metal and metal atoms (M–M). The potential functions for C–M and M–M bonds were established from the results of ab initio calculations. The growth of high-quality SWNTs was simulated at a suitable temperature and supply ratio of carbon atoms. The potential energy of carbon atoms was strongly dependent on the number of C–C and C–M bonds. The dependence explains the growth process, including cap formation, its lift-off, and the continuous SWNT growth

Digital Isotope Coding to Trace the Growth Process of Individual Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWCNTs) are attracting increasing attention as an ideal material for high-performance electronics through the preparation of arrays of purely semiconducting SWCNTs. Despite significant progress in the controlled synthesis of SWCNTs, their growth mechanism remains unclear due to difficulties in analyzing the time-resolved growth of individual SWCNTs under practical growth conditions. Here we present a method for tracing the diverse growth profiles of individual SWCNTs by embedding digitally coded isotope labels. Raman mapping showed that, after various incubation times, SWCNTs elongated monotonically until their abrupt termination. <i>Ex situ</i> analysis offered an opportunity to capture rare chirality changes along the SWCNTs, which resulted in sudden acceleration/deceleration of the growth rate. Dependence on growth parameters, such as temperature and carbon concentration, was also traced along individual SWCNTs, which could provide clues to chirality control. Systematic growth studies with a variety of catalysts and conditions, which combine the presented method with other characterization techniques, will lead to further understanding and control of chirality, length, and density of SWCNTs