Abstract
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 SiO2-covered Si (SiO2/Si) and oxygen-free Si3N4-covered Si (Si3N4/Si) as substrates for supporting Fe films. Well-aligned CNTs were synthesized at a higher growth rate on Si3N4/Si compared with those on SiO2/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.