Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 11: C/diamond
HL 11.8: Vortrag
Montag, 25. Februar 2008, 12:45–13:00, EW 202
The intermediate frequency modes in the carbon nanotube Raman spectra — •Martin Weiß1, Hagen Telg1, Janina Maultzsch1, Viera Skákalová2, and Christian Thomsen1 — 1Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany — 2Max Planck Institut for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
The carbon nanotube Raman spectrum as it is commonly referred to consists of three features, the radial breathing mode (RBM), the high energy modes and the defect induced D mode. These modes are used to gain information on the diameter distribution, the presence of metallic tubes, the defect density and even the precise chiral indices (n1,n2) of the tubes in a nanotube sample. However, apart from these three modes the nanotube Raman spectrum contains features in the intermediate frequency range of which the scattering mechanism is not yet consistently understood. These modes in part result from second-order scattering and resemble the phonon density of states. Therefore, they can give information on the phonon dispersion of nanotubes and on Raman inactive modes. We performed resonant Raman measurements of the intermediate frequency modes (IFM) located between ∼ 400 and ∼1000 cm−1. By comparing the resonance conditions of the IFMs and RBMs we assign the IFMs to certain groups of nanotubes (n1,n2). Furthermore we discuss the dependence of the IFMs on excitation energy and their lineshapes with respect to the calculated phonon density of states.