  We probed the charge transfer interaction between the amine-containing
molecules: hydrazine, polyaniline and aminobutyl phosphonic acid, and carbon
nanotube field effect transistors (CNTFETs). We successfully converted p-type
CNTFETs to n-type and drastically improved the device performance in both the
ON- and OFF- transistor states utilizing hydrazine as dopant. We effectively
switched the transistor polarity between p- and n- type by accessing different
oxidation states of polyaniline. We also demonstrated the flexibility of
modulating the threshold voltage (Vth) of a CNTFET by engineering various
charge-accepting and -donating groups in the same molecule.
