Evaluation of optimum sheath electric field and minimum catalyst interval for selective production of metallic carbon nanotubes

We estimate the optimum electric field at the sheath edge and the minimum interval among nanotubes to promote the growth of armchair-type nanotubes (metallic character) as a function of the nanotube length. On the basis of the electric charge distribution in a nanotube and the optimum electric field E ₁* at the tip of a nanotube evaluated using the Hückel-Poisson method, we calculate the structure of the electric field lines outside a nanotube in the sheath region. As the nanotube length increases, E₁* decreases. To maintain the chemical activity at the tip, the sheath electric field must be decreased. We show the decreasing rate of the sheath electric field with respect to the nanotube length.