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RESEARCH PRODUCT

Raman Spectroscopy and Low-Temperature Transport Measurements of Individual Single-Walled Carbon Nanotubes with Varying Thickness

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We have investigated two metallic and one semiconducting individual single-walled carbon nanotubes (SWNT) and one bundle of two semiconducting nanotubes with a diameter range 1.1−2.9 nm with Raman spectroscopy and low-temperature electric transport measurements. With these two methods, we obtain mutually independent measurements on the basic properties of a specific nanotube. In particular, we obtain data on metallic and semiconducting properties. Evidence of a small band gap for one metallic tube was obtained. For the semiconducting SWNTs with diameters of 2.7−2.9 nm, a special resonance condition was observed which causes an anomalous intensity ratio for the two components of the G-band. This effect has been observed previously for a few tubes with a diameter of 1.6 nm (Jorio, A; et al. Phys. Rev. B 2002, 65, 155412), and our current findings are in agreement with the previously given explanation of the effect and suggest that the effect is common among thick SWNTs. We also obtain evidence that the curr...