Electron microscopy investigation at the initial growth stage of carbon nanotubes

The growth mechanism and the geometry of carbon nanotubes (CNTs) are affected by several parameters such as formation process and catalytic materials. In order to understand the growth mechanism of CNT, it is essential to observe the CNTs at the initial growth stage. We synthesized CNTs directly on the Ni-deposited TEM Cu mesh grid using thermal CVD so as to preserve and investigate the original structure of CNTs from the initial to final growth state without any artifacts that might be introduced during TEM specimen preparation. The results obtained from the electron microscopy study show that the following growth modes of CNTs occur simultaneously at the initial stage: tip-growth, base-growth and intermediate-growth mode. The intermediate growth structure can be achieved by a mixture of base-growth mode and tip-growth mode, which occur sequentially. This is thought to be a probable mechanism for nanotube junctions.