Extreme oxygen sensitivity of electronic properties of carbon nanotubes

The electronic properties of single-walled carbon nanotubes are shown here to be extremely sensitive to the chemical environment. Exposure to air or o xygen dramatically influences the nanotubes' electrical resistance, thermoe lectric power, and Local density of states, as determined by transport meas urements and scanning tunneling spectroscopy. These electronic parameters c an be reversibly "tuned" by surprisingly small concentrations of adsorbed g ases, and an apparently semiconducting nanotube can be converted into an ap parent metal through such exposure. These results, although demonstrating t hat nanotubes could find use as sensitive chemical gas sensors, Likewise in dicate that many supposedly intrinsic properties measured on as-prepared na notubes may be severely compromised by extrinsic air exposure effects.