Influence of the substrate types and treatments on carbon nanotube growth by chemical vapor deposition with nickel catalyst.

Our investigation aimed at the development of a process capable of producing well ordered, vertically aligned carbon nanotubes (CNTs) arrays, with reproducible properties, for applications such as a position particle detector and a cold cathode emitter for storage devices. The results on catalyst nanoparticles formation from a thin Ni film evaporated on SiO2 and Si3N4 substrates are presented. The substrate-catalyst layers have been processed in several gaseous atmospheres and in the temperature range 700-900°C in order to obtain the most appropriate morphology, size and density of the nanoparticles for the subsequent CNTs growth. The smallest nanoparticles have been obtained on the SiO2 substrate in H2 atmosphere and at the lowest temperature 700°C. However, the best vertically aligned and well graphitized CNTs resulted from the NH3 annealing process followed by the deposition of CNTs at 900°C in C2H2 and NH3.