Following the surprising finding of nanocarbon materials such as carbon nanotube (CNT) and graphene, Kondo et al. reported chemical vapor deposition (CVD) growth of a novel composite structure consisting of graphene multi-layers (graphite) supported by vertically aligned multi- walled CNTs in 2008 [1]. Because of its unique structure, novel applications are expected such as a via-hole wiring material of electronic circuitry. Understanding of the growth mechanism of the composite crucial for the realization of such novel devices.
At present, however, details of the growth mechanism in terms of carbon supply processes and growth dynamics, namely, tip growth or root growth, have been unexplored. In this talk we investigate the growth mechanism through the systematic and precise experiment and analysis using combinatorial masked deposition (CMD) method and HOF (Herman’s orientation factor) method. Firstly we compare the composite growths using catalyst of Fe and Co, which is known to catalyze different quality of carbons. The CNT arrays grew at thick iron film, while only graphite film was precipitated at thick cobalt film without growth of CNTs arrays. This result was explained by the fact that carbon atoms are supplied through the defects in the graphitic forms to the catalyst, and cobalt catalyst is deactivated before starting the CNTs growth due to fewer defects in the precipitated graphitic forms[2].
Next, the degree of the CNTs alignment in the composite was in detail analyzed by HOF. It is found that the base-growth mode is most favorable for the growth of the CNTs arrays under the top graphite film, which is different from the previous study by Kondo. Based on the above results, a new mechanism for the composite growth is proposed.
[1]D. Kondo et al., Appl. Phys. Express, 1 (2008) 074003.
[2]Y. Matsuoka and M. Yoshimura, Jpn. J. Appl. Phys., in press.
BIO - prof. Masamichi Yoshimura
Masamichi Yoshimura is currently a professor at Surface Science Laboratory at Toyota Technological Institute, Japan. He received his Ph.D. from University of Tokyo in Applied Physics. He is author and coauthor of more than 170 scientific papers .
