Donor and acceptor-like electronic states in a one-dimensional semiconductor

Donor and acceptor-like electronic states were observed near the conduction and valence band, respectively, in a semiconducting single-wall carbon nanotube using scanning tunneling microscopy and spectroscopy. They are observed to be, spatially, at the same location and spread within a few nm. Their physical origin is suggested as locally formed excessive and deficient number of electrons per a closed carbon network.