Carbon nanotube growth from metallic nanoparticles deposited by pulsed-laser deposition on different substrates

Abstract

Carbon nanotubes carpets were grown by RF plasma enhanced chemical vapor deposition on various substrates coated by Fe and Ni transition metals that act as catalyst. C2H2 gas was used for the carbon source. The results show that carbon nanotubes CNT can be grown on Si3N4/Si and SiO2/Si substrates only with an Fe catalyst. They are typically formed by multi-walled graphene layers, and can be obtained for a temperature as low as 550°C. Nanotubes grown on TiN/SiO2/Si substrate from Fe or Ni catalysts present bamboo-like nanostructures and are obtained for particular experimental conditions. This study demonstrates substrate-to-catalyst effect on the CNT growth and their microstructures indicating that the adhesion force of nanoparticles on substrates is a main parameter. Catalyst particles are spherical and several tens of nm in diameter (weak adhesion strength) when deposited onto SiO2/Si or Si3N4/Si, the tip growth mode of nanotube is favored. On TiN/SiO2/Si substrate, particles are larger (large adhesion strength) and CNT growth is no more in tip mode, bamboo-like structures are obtained. When an Fe-Ni catalyst multilayer has been deposited onto the different substrates, carbon nanotube microstructures show multi-walled graphene parallel layers on Si3N4/Si and SiO2/Si insulating substrates, and bamboo-like microstructures on TiN/SiO2/Si conductor substrate.