Phonons in alkali-doped single-wall carbon nanotube bundles

Abstract

We review Raman spectroscopy of alkali-doped single-wall carbon nanotube bundles. These results are correlated to resistivity and optical absorption measurements performed on the same samples. In this review we focus on the behavior of the high-frequency tangential modes upon doping. A doping-induced upshift of the tangential modes, concomitant to a loss of absorption bands in the optical spectra and to a monotonic decrease of the resistivity, is stated. The Raman response measured on the first plateau of the resistivity curve is featured by a symmetric single component upshifted with respect to pristine sample. This response is assigned to the Raman signature of a specific doped phase, labelled phase I. By contrast the Raman response of the saturated phase, associated to a second plateau in the resistance curve, is featured by a Breit–Wigner–Fano component downshifted with respect to the pristine sample.