Current-controlled nanotube growth and zone refinement

Abstract

We describe methods by which the growth of a single carbon nanotube (CNT) can be precisely controlled by an electrical current. In one method a CNT is grown to a predetermined geometry inside another nanotube, which serves as a reaction chamber. Another method allows a preexisting marginal-quality multiwall CNT to be zone refined into a higher-quality multiwall CNT by driving a catalytic bead down the length of the nanotube. In both methods, the speed of nanotube formation is adjustable, and the growth can be stopped and restarted at will.