Unveiling the Evolutions of Nanotube Diameter Distribution during the Growth of Single-Walled Carbon Nanotubes

In situ and ex situ Raman measurements were used to study the dynamics of the populations of single walled carbon nanotubes (SWCNTs) during their catalytic growth by chemical vapor deposition. Our study reveals that the nanotube diameter-distribution strongly evolves during SWCNT growth but in dissimilar ways depending on the growth conditions. We notably show that high selectivity can be obtained using short or moderate growth times. High-resolution transmission electron microscopy observations support that Ostwald ripening is the key process driving these seemingly contradictory results by regulating the size distribution and lifetime of the active catalyst particles. Ostwald ripening appears as the main termination mechanism for the smallest diameter tubes, whereas carbon poisoning dominates for the largest ones. By unveiling the key concept of dynamic competition between nanotube growth and catalyst ripening, we show that time can be used as an active parameter to control the growth selectivity of carbon nanotubes and other 1D systems.