Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 11: Carbon: Nanotubes, Diamond and Silicon Carbid

HL 11.8: Talk

Monday, March 26, 2012, 13:30–13:45, EW 203

Permanent Dipole Moments of Localized Carbon Nanotube Excitons — •Jan Glückert, Matthias Hofmann, and Alexander Högele — Fakultät für Physik and Center for Nano Science (CeNS), Ludwig-Maximilians-Universität, München, Germany

Semiconducting single-walled carbon nanotubes exhibit photoluminescence emission in the near infrared due to recombination of excitons [1-3]. Recent observation of photon anti-bunching in the cryogenic photoluminescence of individual nanotubes suggests that exciton localization at low temperatures dominates the spectral response [4].

We investigate the emission spectra of individual CoMoCat nanotubes as a function of external electric field. We fabricated a sample that allows us to apply static electric fields perpendicular to the nanotube axis and record their spectral response in a confocal microluminescence setup at cryogenic temperatures.

We observe spectral shifts up to several linewidths and a linear dependence of the emission energy on the electric field. We interpret our findings in terms of a linear DC Stark effect due to permanent dipole moments of localized excitons. From the linear slope we deduce values for the exciton dipole moments and find a sub-Angstrom electron-hole separation.

[1] M. J. O'Connell et al., Science 297, 593 (2002).

[2] J. Maultzsch et al., Physical Review B 72, 241402 (2005).

[3] F. Wang et al., Science 308, 838 (2005).

[4] A. Högele et al., Physical Review Letters 100, 217401 (2008).