Toshiba (Tokyo, JP) filed U.S. Patent Application 20100209704 for a carbon nanotube growing process, and carbon nanotube bundle formed substrate.
According to inventorsYuichi Yamazaki, Tadashi Sakai, Naoshi Sakuma, Masayuki Katagiri, Mariko Suzuki and Shintaro Sato, in the growth of carbon nanotubes, the aggregation of catalytic fine particles therefor is a problem. By subjecting a catalytic thin film or catalytic fine particles to the multistage plasma pretreatment, carbon nanotubes can be grown into a high density.
In order to realize the growth of carbon nanotubes into a high density, the Toshiba carbon nanotube growing process includes a first plasma treatment step of treating a surface having catalytic fine particles with a plasma species generated from a gas which contains at least hydrogen or a rare gas without carbon element, a second plasma treatment step of forming a carbon layer on the surface of the catalytic fine particles by a plasma generated from a gas which contains at least a hydrocarbon after the first plasma treatment step, and a carbon nanotube growing step of growing carbon nanotubes by use of a plasma generated from a gas which contains at least a hydrocarbon after the second plasma treatment step.
As a process for growing carbon nanotubes, known are an arc discharge method, a laser ablation method, a liquid phase method and others. From the viewpoint of productivity, controllability and consistency with semiconductor processes, chemical vapor deposition (CVD) is superior. Out of CVD methods, a catalytic CVD method is general, wherein catalytic fine particles made of Fe, Co, Ni or the like are deposited on a substrate, and carbon nanotubes are grown thereon. At present, high-quality carbon nanotubes can be relatively easily obtained, which have a density of the first half of the order of 1011 cm-2.