Density control of aligned carbon nanotubes from controlled deposition of Fe catalyst nanoparticles using the filler-added Langmuir–Blodgett technique

Abstract A filler-added Langmuir–Blodgett (LB) technique was developed to control the number density of Fe catalyst nanoparticles to grow vertically aligned carbon nanotubes (VACNTs). Palmitic acid was chosen as the filler molecule. This technique enabled the distribution of iron nanoparticles (FeNPs) with a number density of 4.2 × 10 9 to 8.7 × 10 10  cm − 2 with a mean distance between particles of 36–170 nm, and the growth of VACNTs. The change in the FeNP number density was controlled after each preparation step. The FeNP number density in the Langmuir film could be controlled at a target value by adding filler to the FeNPs dispersion solution when preparing the Langmuir film. Approximately 30% of the FeNPs were transferred from Langmuir film to LB film on substrate, and in the subsequent thermal chemical vapor deposition (CVD) process, the density further decreased to approximately 20%. In summary, the FeNP number density decreased to approximately 6% of the controlled number density in the Langmuir film. The FeNPs catalyzed the growth of VACNTs during the thermal CVD process.