Effect of substitutional atoms in the tip on field-emission properties of capped carbon nanotubes

By use of first-principles calculations, we investigate the effect of introducing substitutional boron or nitrogen atom in the tip on field-emission properties of capped single-wall carbon nanotubes. We find that the substitution in the tip can significantly enhance the localized density of states at the Fermi level, which is important for field emission. The substitution of nitrogen introduces unsaturated dangling bond states at the tip, yielding a reduction of the work function of the tip. Our results suggest that the capped tube with substitutional nitrogen or boron atom in the tip could have much larger field-emission current than the tube without substitution. (C) 2002 American Institute of Physics.