Effects of oxygen and nitrogen on carbon nanotube growth using a microwave plasma chemical vapor deposition technique

In this paper, we studied the effects of oxygen (O2) and nitrogen (N2) on the growth of carbon nanotubes (CNTs) prepared using microwave plasma-enhanced chemical vapor deposition (MPECVD). CNTs were prepared with 20–100-nm-sized Ni catalyst grains under three different groups of plasma conditions. Scanning electron microscopy (SEM) results show that the quality of CNTs is improved and number density greatly increased with addition of N2 and O2 in the process. The morphology and Ni composition strongly suggest that the grain size and composition of the Ni catalyst can be modified by the N2 and O2 plasma pretreatments. A nitride-enhanced growth mechanism is also discussed.