Electron emission and structural characterization of a rope of single-walled carbon nanotubes

The electron emission and structural properties of an isolated ''rope'' comprised of similar to 70 individual single-walled nanotubes (SWNT's) were investigated by measuring the field-emission energy distributions and by using field-ion microscopy (FIM). Field-emission energy distributions, obtained under ultrahigh-vacuum conditions, revealed that the emitting nanotube has a large density:of;states near the Fermi energy, with an energy distribution of emitted electrons close to that predicted by the free-electron theory. Two small features located on the trailing edge of the energy distributions are attributed to localized features in the density of states of a SWNT. FIM studies were also performed on the same rope in an attempt to provide structural information about the emitting nanotube. Initial FIM micrographs showed:an uneven distribution of atoms. Eventually, rings of atoms were imaged. The atom placement around an individual ring structure is analyzed and found to be consistent with that expected from a single (19,13) SWNT.