Applied Physics

Switching Carriers on Contact

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Science  21 Dec 2001:
Vol. 294, Issue 5551, pp. 2431
DOI: 10.1126/science.294.5551.2431a

Carbon nanotube field-effect transistors (CNT-FETs) are ambipolar devices—they can use either negatively or positively charged current carriers (electrons or holes) and thus can be biased in either direction. If carbon nanotubes are to replace semiconductors in even smaller FETs, then ways must be found to make them ambipolar as well. Adsorption or desorption of certain gases at the CNT surface can reverse the carrier type, but such a route to control the electronic properties does not seem practical.

Martel et al. have now prepared an ambipolar CNT-FET in which the titanium (Ti) source and drain contacts to the CNT are modified by annealing at high temperature to form abrupt crystalline TiC contacts. Subsequent modulation of the barrier height of TiC/CNT junction by the gate bias allows switching of the conduction along the CNT between holes and electrons. Such robust and controllable ambipolar action is analogous to the complementary metal oxide semiconductor technology of today's microelectronics sector.—ISO

Phys. Rev. Lett.87, 256805 (2001).

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