Thermal chemical vapor deposition (T-CVD) growth of carbon nanotubes on different metallic underlayers

The synthesis of carbon nanotubes (CNTs) on various substrates by thermal chemical vapor deposition (T-CVD) (500–800 °C) is described. C2H2 (98% purity) is used as the carbon feedstock and the metallic underlayers, i.e., AlCu, Cu, Ag, Ta, and NiV are used. A crucial component is the insertion (or inclusion) of an Al layer between the metal and the catalyst, which then leads to the effective growth of CNTs. The types of CNTs (single or multi walled) could be dependent on the diameter of AlxOy nanoparticles that are formed during the annealing process. In situ mass spectroscopy reveals that the increase in CO2 and H2O with temperature, during the growth, could be correlated to the formation of longer CNTs (∼2 μm) on NiV and Ta due to their etching effects (i.e. C+CO2→2CO and C+H2O→CO+H2).