Electric effects in nanotube growth Original Research Article

We present experimental evidence that strongly supports the hypothesis that the electric field of the arc plasma is essential for nanotube growth in the arc by stabilizing the open tip structure against closure. By controlling the temperature and bias voltage applied to a single nanotube mounted on a macroscopic electrode, we find that the nanotube tip closes when heated to a temperature similar to that in the arc unless an electric field is applied. We have also developed a more refined awareness of “open” tips in which adatoms bridge between edge atoms of adjacent layers, thereby lowering the exothermicity in going from the open to the perfect dome-closed tip. Whereas realistic fields appear to be insufficient by themselves to stabilize an open tip with its edges completely exposed, the field-induced energy lowering of a tip having adatom spot-welds can, and indeed in the arc does, make the open tip stable relative to the closed one.