Optical Properties and Raman Spectroscopy of Carbon Nanotubes

Riichiro Saito1 and Hiromichi Kataura2

1 Department of Electronic-Engineering, The University of Electro-Communications

1-5-1, Chofu-gaoka, Chofu, Tokyo 182-8585, Japan [email protected]

2 Department of Physics, Tokyo Metropolitan University 1-1 Minami-Ohsawa, Hachioji, Tokyo 192-0397, Japan [email protected]

Abstract. The optical properties and the resonance Raman spectroscopy of single wall carbon nanotubes are reviewed. Because of the unique van Hove singularities in the electronic density of states, resonant Raman spectroscopy has provided diameter-selective observation of carbon nanotubes from a sample containing nanotubes with different diameters. The electronic and phonon structure of single wall carbon nanotubes are reviewed, based on both theoretical considerations and spec-troscopic measurements.

The quantum properties of Single-Wall Carbon Nanotubes (SWNTs) depend on the diameter and chirality, which is defined by the indices (n,m) [1,2]. Chirality is a term used to specify a nanotube structure, which does not have mirror symmetry. The synthesis of a SWNT sample with a single chirality is an ultimate objective for carbon nanotube physics and material science research, but this is still difficult to achieve with present synthesis techniques. On the other hand, the diameter of SWNTs can now be controlled significantly by changing the furnace growth temperature and catalysts [3,4,5,6]. Thus, a mixture of SWNTs with different chiralities, but with a small range of nanotube diameters is the best sample that can be presently obtained. Resonance Raman spectroscopy provides a powerful tool to investigate the geometry of SWNTs for such samples and we show here that metallic and semiconducting carbon nanotubes can be separately observed in the resonant Raman signal.

In this paper, we first review theoretical issues concerning the electron and phonon properties of a single-walled carbon nanotube. We then describe the electronic and phonon density of states of SWNTs. In order to discuss resonant Raman experiments, we make a plot of the possible energies of optical transitions as a function of the diameter of SWNTs.

Then we review experimental issues concerning the diameter-controlled synthesis of SWNTs and Raman spectroscopy by many laser frequencies. The optical absorption measurements of SWNTs are in good agreement with the theoretical results.

M. S. Dresselhaus, G. Dresselhaus, Ph. Avouris (Eds.): Carbon Nanotubes, Topics Appl. Phys. 80, 213-247 (2001) © Springer-Verlag Berlin Heidelberg 2001

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