Plasma-induced alignment of carbon nanotubes

Uniform films of well-aligned carbon nanotubes have been grown using microwave plasma-enhanced chemical vapor deposition. It is shown that nanotubes can be grown on contoured surfaces and aligned in a direction always perpendicular to the local substrate surface. The alignment is primarily induced by the electrical self-bias field imposed on the substrate surface from the plasma environment. It is found that switching the plasma source off effectively turns the alignment mechanism off, leading to a smooth transition between the plasma-grown straight nanotubes and the thermally grown “curly” nanotubes. The nanotubes grow at a surprisingly high rate of ∼100 nm/s in our plasma process, which may be important for large-scale commercial production of nanotubes.