Defect Structure of Multiwalled Carbon Nanotubes Studied by Raman Spectroscopy

The defect structure of multiwalled carbon nanotubes has been studied by transmission electron microscopy and Raman spectroscopy, with particular attention to the shape and intensity of the defect band D and its overtone D*. Electron-microscopic results demonstrate that multiwalled nanotubes typically have multiple bends. The associated short- and long-range disorder influences the Raman spectrum of the nanotubes. The presence of several defect species, differing in scattering probability, results in a stochastic relationship between the intensities of the D*- and D-bands. This relationship is qualitatively interpreted in terms of general mechanisms of elastic/inelastic interactions of pi-electrons with phonons and defects.