Pulsed plasma-induced alignment of carbon nanotubes

The growth of uniform films of well-aligned carbon nanotubes (CNTs) using pulsed plasma-enhanced chemical vapor deposition is reported here. It is demonstrated that nanotubes can be grown on a certain critical catalyst film thickness and that their alignment is primarily induced by pulsed plasma excitation time. It is, in fact, found that switching the plasma source for 0.1 s effectively turns the alignment mechanism on, leading to a sharp transition between the pulsed plasma-grown straight nanotubes and continuous plasma-grown curly nanotubes. Raman spectroscopy was successfully applied to confirm that, by employing a suitable plasma excitation time, it is possible to obtain the growth of nanotubes with a limited presence of amorphous carbon on the substrate surface. The pulsed biasing technique offers an efficient method to adjust the CNTs' alignment by independent control of the neutral radical and ion fluxes to the surface.