Structural dependence of excitonic optical transitions and band-gap energies in carbon nanotubes.

Dukovic, Gordana; Wang, Feng; Song, Daohua; Sfeir, Matthew Y; Heinz, Tony F; Brus, Louis E · Nano Lett · 2005

basic_science · Level V

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Abstract

The optical transitions of semiconducting carbon nanotubes have been ascribed to excitons. Here we use two-photon excitation spectroscopy to measure exciton binding energies, as well as band-gap energies, in a range of individual species of semiconducting SWNTs. Exciton binding energies are large and vary inversely with nanotube diameter, as predicted by theory. Band-gap energies are significantly blue-shifted from values predicted by tight-binding calculations.