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
/?m 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.
