Controlling the shape of a carbon nanotube by using the reaction chamber pressure
We report the effects of the reaction chamber pressure on the shape and the structure of verticallyaligned carbon nanotubes (CNT) grown on a Ni catalyst by using dc plasmaenhanced chemical vapor deposition system. By controlling the pressure of the reaction chamber We were able to alter the shape and the crytallinity of CNTs. With increasing the chamber pressure, the length was rapidly reduced from 4.5 /μm to 800 nm, but the crytallinity was strongly enhanced. As the reaction chamber pressure decreases, the tips of the CNTs were observed to change from a hemispherical tip with one conical Ni particle to a distorted the tip with more than one tiny Ni particle which means that the formation of Ni conglomerates does not only occur during the pretreatment process but also continues during the CNT growth process. These results have further clarified the role of the reactive etching ions in the growth of CNTs.