Effects of oxygen on the electron transport properties of carbon nanotubes: Ultraviolet desorption and thermally induced processes

Highly sensitive electrical response of carbon nanotubes to UV exposure and thermal treatments are examined. Low intensity UV-induced conductivity change in individual single-walled carbon nanotube transistors is found to be mainly arising from oxygen desorption at the metal contacts rather than from nanotubes or possible amorphous side products. Choice of metal or thermal annealing (which changes the metal-nanotube contacts) eliminates or minimizes this low intensity UV response. However, a slow p-doping process is observed upon thermal annealing followed by equilibration in O-2 or air as suggested by changes in the near infrared spectra of nanotube films and in individual nanotube transport characteristics.