We investigated the effect of oxygen incorporated in substrates for forming Fe-based catalytic particles and growing carbon nanotubes (CNTs) by water-assisted catalytic chemical vapor deposition. We examined two types of SiO 2 -covered Si (SiO 2 /Si) and oxygen-free Si 3 N 4 -covered Si (Si 3 N 4 /Si) as substrates for supporting Fe films. Well-aligned CNTs were synthesized at a higher growth rate on Si 3 N 4 /Si compared with those on SiO 2 /Si. The compositions of Fe-based catalytic particles that were formed by heating the substrates were examined using X-ray photoelectron spectroscopy (XPS) to determine the differences. Results show that the concentration ratio of Fe to Fe oxide in the catalytic particles strongly affects the alignment and height of synthesized brushlike CNTs and is well optimized in oxygen-free substrates.
The key technologies to achieve mass production of brushlike multiwalled carbon nanotubes (CNTs) are rapid processing for substrate heating and growing CNTs, and then cooling the substrate. We used chemical vapor deposition at 800 °C with a carbon source gas of acetylene to investigate how substrate heating rate affects CNT growth. The results revealed an effective layered structure of an Fe catalyst for the rapid heating process: an oxidized Fe layer and a metal Fe layer formed on a silicon dioxide layer. The relationship among the given structure of Fe catalysts, the catalyst shape after rapid heating, and the resultant CNTs were investigated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.