Localized Electroluminescence of Single-Wall Carbon Nanotubes

Carbon nanotube field-effect transistors emit mobile light emission in the ambipolar regime. In the presence of heterogeneities in the local environment of the nanotube, stationary electroluminescence is also observed in the unipolar regime, where minority carriers must be generated locally. This stationary, localized luminescence can be correlated with changes in the transport current and with an altered movement of the ambipolar light-emitting spot during gate- and source-drain-voltage sweeps. Hence, the stationary electroluminescence is crucial for identifying “environmental defects” in carbon nanotubes and for evaluating their role in electronic transport. We explore spontaneously doped nanotube segments, which lead to local carrier inversion and electroluminescence. In partially polymer-covered nanotubes, light emission originates at the polymer boundaries, which introduce potential steps along the carbon nanotube. The Schottky contacts of the nanotube field-effect transistors produce large local fields, facilitating light emission. Finally in nanotubes with loops, we observe localized emission at the base of the loops but do not observe ambipolar light emission from the loops. By using scanning SQUID microscopy on these samples, we measure a finite unipolar current flowing around such loops and show that the nanotube-nanotube junctions at the base of the loops pin the ambipolar emission.

By: M. Freitag; J. C. Tsang; J. Kirtley; A. Carlsen; J. Chen; A. Troeman; H. Hilgenkamp; Ph. Avouris

Published in: RC23706 in 2005


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