• Sato, T.
• Bando, Y.
• Bourgeois, L.
• Kurashima, K.

Abstract

<p>Bundles of B- and N-doped single-walled carbon nanotubes (SWNTs) containing up to approximately 10 at% B and up to approximately 2 at% N were synthesized at high yields under thermo-chemical treatment of pure C SWNT bundles and B₂O₃ in a flowing nitrogen atmosphere. The bundles were characterized by means of high-resolution transmission electron microscopy and electron energy loss spectroscopy. The effects of synthesis temperature (1503-1773 K) and time (30-240 min) on the B and N contents and yield of the SWNT bundles were determined. The maximum yield of the B- and N-doped SWNT bundles was obtained under synthesis at 1553 K over 30 min. Atomic structure and morphology of individual SWNTs in the bundles, in particular, packing of doped SWNTs, helicity distribution, encapsulation of fullerene-like clusters, diameter and shell number variations were studied. The synthesized SWNTs in the bundles were stacked in a honeycomb array with the uniform inter-tube spacing of approximately 0.3 nm. No preferable orientation for the graphene-like tubular shells was found, i.e. both zigzag and armchair edges were observed with approximately equal proportions. Frequently, diameter increase took place for the outer tubes in a bundle and for isolated SWNTs. C-based or BN-based fullerene-like encapsulates were observed in individual SWNTs. Carbon oxidation by the B₂O₃ vapor and B and N substitution for C is thought to underlie the doping of C SWNTs. The substitution reaction temperature-time limits with respect to the morphological stability of B- and N-doped SWNT bundles are finally elucidated.</p>

Topics

• impedance spectroscopy
• cluster
• Carbon
• nanotube
• Nitrogen
• transmission electron microscopy
• electron energy loss spectroscopy