Electronics and Optoelectronics with Single Carbon Nanotubes
nanotubes, nanoelectronics, optoelectronics
Invited Talk: Carbon nanotubes (CNTs) are 1D nanostructures with properties ideal for applications in nano- and opto-electronics. Strong emphasis has been placed on the fabrication of CNT field-effect transistors (CNTFETs). In general, charge-transfer at the CNT-metal interfaces leads to the formation of Schottky barriers, which adversely affect the performance of the FET. Furthermore, upon scaling of the gate insulator thickness, unipolar CNTFETs turn ambipolar with large leakage currents. We eliminated these problems by: (a) electrostatic doping of the contacts, and (b) chemical doping with adsorbed molecules. The resulting unipolar CNTFETs have outstanding operational characteristics. Ambipolar CNTFETs are particularly valuable in photonics. We have used a-CNTFETs to inject electrons and holes from the opposite terminals of the FET. A fraction of these carriers recombine radiatively. Thus, we produce an electrically-excited single nanotube molecule light source. Unlike conventional p-n diodes, a-CNTFETs are not doped and there is no fixed p-n interface. By spatially resolving the emission we found that the emitting region can be translated at will along a CNTFET channel by varying the gate voltage. Study of the properties of the emission as a function of applied bias provides new insights on the electrical transport in CNTs. Stationary light spots are also observed and their generation mechanism involving defects is analyzed. Finally, I will present photoconductivity spectra of individual CNTs that provide information on the nature of the excited states of the CNTs.
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Nanotech 2005 Conference Program Abstract