Phases of Carbon Nanotube Growth and Population Evolution from in Situ Raman Spectroscopy during Chemical Vapor Deposition

The dynamical evolution of nanotube chemical vapor deposition growth was investigated by in situ spectroscopy of three main Raman bands: G, D, and RBM. The evolution in diameter distribution is inferred from RBM and G bands, and the evolution in crystallinity is determined from D and G bands. A consistent sequence of the growth evolution is observed, with four discernible phases: incubation, acceleration, linear growth, and termination. The temperature dependence of each of these stages of growth is experimentally determined, and characteristic energy scales apparently associated with each phase are extracted. The growth becomes slower as the temperature increases, with activated, parasitic reactions suggested as a cause. We explore to what extent one diameter grows in comparison to another and thus gain some insight into how the nanotube population changes with time.