Electrical and Raman Spectroscopic Studies of Vertically Aligned Multi-Walled Carbon Nanotubes

Microwave plasma enhanced chemical vapour deposition (MPECVD) was used for the production of carbon nanotubes. Vertically aligned multi-walled carbon nanotubes (MWCNTs) were grown on silicon substrates coated with cobalt thin films of thickness ranging from 0.5 nm to 3 nm. Prior to the nanotube growth the catalyst were treated with N₂ plasma for 5–10 minutes that break the films into small nanoparticles which favour the growth of nanotubes. The CNTs were grown at a substrate temperature of 700 °C for 5, 10 and 15 minutes. The height of the CNT films ranging from 10 μm–30 μm indicating that the initial growth rate of the CNTs are very high at a rate of approximately 100 nm/sec. Electrical resistivity of the above samples was evaluated from I–V measurements. The activation energy (E _a) was also calculated from the temperature dependent studies and it was found that the E _a lies in the range of 15–35 meV. Raman spectroscopy was used to identify the quality of the nanotubes.