Growth of single-walled carbon nanotubes from sharp metal tips.

The nucleation and growth of single-walled carbon nanotubes is observed in situ in a transmission electron microscope. Carbon atoms are implanted into catalytically active metal particles by electron-beam sputtering. The metal particles are then shaped with a focused electron beam. Once the particles have a region of high surface curvature, spontaneous nucleation and growth of single-walled carbon nanotubes occurs on the metal particles. It is shown that the local solubility of carbon in the metal determines the nucleation of nanotubes. This is confirmed by atomistic computer simulations treating the solubility of carbon in a metal particle as a function of the size of the system.