Electroluminescence from chirality-sorted (9,7)-semiconducting carbon nanotube devices

We have measured the electroluminescence and photoluminescence of (9,7)-semiconducting carbon nanotube devices and demonstrate that the electroluminescence wavelength is determined by the nanotube's chiral index (n,m). The devices were fabricated on Si₃N₄-membranes by dielectrophoretic assembly of tubes from monochiral dispersion. Electrically driven (9,7)-devices exhibit a single Lorentzian-shaped emission peak at 825 nm in the visible part of the spectrum. The emission could be assigned to the excitonic E22 interband-transition by comparison of the electroluminescence spectra with corresponding photoluminescence excitation maps. We show a linear dependence of the EL peak width on the electrical current, and provide evidence for the inertness of Si₃N₄ surfaces with respect to the nanotubes optical properties.