Plasma-Induced Conformal Alignment of Carbon Nanotubes on Curvatured Surfaces

We have successfully demonstrated the growth of conformally aligned carbon nanotubes using microwave plasma enhanced chemical vapor deposition (MPECVD) processes. The nanotubes are grown always perpendicular to the local substrate surface regardless of the surface contour or curvature, with an extreme-case example of conformal radial growth of nanotubes on the surface of a hair-thin optical fiber glass. The electrical self-bias imposed on the substrate surface in the microwave plasma environment appears to be the primary mechanism responsible for the conformal alignment. The nanotubes grow rapidly from their bases with a strong correspondence between nanotube diameter and catalyst size. We shoe that by turning on or off the plasma source, which effectively turns on or off the alignment mechanism, defective structure can be deliberately introduced at the physical junction between a plasma-grown straight nanotube and a thermally-grown "curly" nanotube. The new, conformally aligned nanotube structure and the ability to controllably introduce defective structure along the length of a growing nanotube are potentially important for building useful devices based on carbon nanotubes.