Studies of multiwall carbon nanotubes using Raman spectroscopy and atomic force microscopy

We present preliminary results of Raman scattering measurements of multiwall carbon nanotubes (MWCNT). The nanotubes have been carefully dissolved, separated and then characterized by AFM. The micro-Raman spectra of the objects are taken with 514,5nm wavelength excitations and in the temperature range 4K 400K. Basically the spectra are quite similar to the well known single wall carbon nanotube spectra, with the exception of the absence of low frequency band. The major Raman bands, that are observed in single wall nanotubes are found in the spectra. In particular the disorder effects are visible due to the pronounced D band at ~1350 cm -1 . Metallic and semiconducting type of conductitivity is distinguished through an analysis of the G (LO) mode at ~1600 cm -1 . We noticed new feature in these spectra at ~843 cm -1 . Low energy radial breathing mode absence has been also explained.