Electrical transport in pure and boron-doped carbon nanotubes

The resistivities of individual multiwalled pure and boron-doped carbon nanotubes have been measured in the temperature range from 25 to 300 degrees C. The connection patterns were formed by depositing two-terminal tungsten wires on a nanotube using focused-ion-beam lithography. A decrease of the resistivity with increasing temperature, i.e., a semiconductor-like behavior, was found for both B-doped and pure carbon nanotubes. B-doped nanotubes have a reduced room-temperature resistivity (7.4 X 10(-7) - 7.7 X 10(-6) Ohm m) as compared to pure nanotubes (5.3 X 10(-6) - 1.9 X 10(-5) Ohm m), making the resistivity of the doped tubes comparable to those along the basal plane of graphite. The activation energy derived from the resistivity versus temperature Arrhenius plots was found to be smaller for the B-doped (55-70 meV) than for the pure multiwalled nanotubes (190-290 meV). (C) 1999 American Institute of Physics. [S0003-6951(99)03021-1].