Regensburg 2010 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 61: Poster II: Materials, Interfaces and Heterostructures

HL 61.12: Poster

Donnerstag, 25. März 2010, 18:00–20:00, Poster D1

Temperature dependent combination modes in the intermediate frequency region of single walled carbon nanotubes — •Felix Fromm, Daniel Niesner, Jonas Röhrl, Ralf Graupner, and Martin Hundhausen — Universität Erlangen-Nürnberg, Lehrstuhl für Technische Physik, 91058 Erlangen, Germany

Single walled carbon nanotube (SWCNT) samples have different diameter distributions, depending on the production method. Resonant Raman scattering can be employed for their characterisation since it is sensitive to the diameters of the SWCNTs. We measured Raman spectra with different laser excitation energies in the temperature range between 10 K to 700 K in order to study SWCNTs produced by the laser ablation (LA) process and the high-pressure catalytic decomposition of carbon monoxide (HiPco). We focus here on the so called intermediate frequency modes (IFMs) which lie in between the well known radial breathing modes (RBMs) and the defect induced D-band. The Stokes Raman spectra of the IFMs contain both one-phonon and two-phonon modes. The two-phonon modes either correspond to the excitation of two phonons or to the excitation of one phonon of higher energy combined with the annihilation of one lower-energy phonon. Since the annihilation is strongly temperature dependent, it is possible to distinguish between these two alternatives. We also estimate the energy of the annihilated phonon from the temperature dependence.