Effects of a Sandwich-Like Catalyst on the Vertical Growth of Carbon Nanotubes Synthesized by Using Chemical Vapor Deposition

The effects of sandwich-like catalysts on the vertical growth of multiwalled carbon nanotubes (MWCNTs) are investigated. We achieved the synthesis of 2.2-mm-long MWCNT forests with carefully designed catalyst films by thermal chemical vapor deposition. Two types of sandwich-like catalysts were prepared by electron beam evaporation. Fe and Al2O3 layers were deposited on a SiO2 surface of 300 nm in thickness. Here, Fe and Al2O3 were used for the catalyst and the supporting buffer layer, respectively. C2H4 was used m a carbon source while Ar and H-2 were used as carrier gases. The sandwich-like catalyst supported by a buffer layer of Al2O3 significantly enhanced the quality of the CNTs. The termination of MWCNT growth was found to depend on the position of the Fe layer. Also, the type of sandwich-like catalyst affects the crystalline perfection of the MWCNTs.