Chemically induced air- stable unipolar-to-ambipolar conversion of carbon nanotube field effect transistors

Air-stable unipolar-to-ambipolar conversion of carbon nanotube field effect transistors has been realized through coating phenyl hydrazine. The concentration of the chemical clusters is found to be a critical parameter of controlling the conduction type and n-type saturation current of the transistors. The Raman spectrum of the nanotube channel shows an increase in the typical disorder band, indicating chemisorptions of the chemical clusters to the side wall of the nanotubes. We suggest that such conversion is caused by desorbing oxygen molecules at the nanotube/Au contacts, so that the Fermi level of Au electrodes shifts into the middle of the nanotube bandgap. (C) 2009 Elsevier B.V. All rights reserved.