Effects of nanodomain formation on the electronic structure of doped carbon nanotubes

Changes in the electronic structure of multiwalled nanotubes due to the introduction of boron in the lattice are identified using scanning tunneling spectroscopy. Doped tubes are metallic with no apparent band gap, in contrast to undoped tubes with varying electronic character. Combined with ab initio calculations, we show that changes in the local density of states, as determined from tunneling spectroscopy, must be interpreted in terms of nanodomains of dopant islands and not as isolated substitutional species.