Combined in situ conductivity and Raman studies of rubidium doping of single-wall carbon nanotubes

Phase transitions and staging in doped single-wall carbon nanotubes (SWNT’s) are controversial issues. Here, we report on combined in situ conductivity and Raman measurements of Rb-doped SWNT’s. Striking correlations between resistance, changes of resistance under laser irradiation, and frequency of the main Raman peak are observed. In the last steps of doping, two different Raman signatures, with peaks at 1596 and $1555\hspace{0.5em}{\mathrm{cm}}^{-1},$ respectively, are observed and assigned to two different stable doped phases. The two phases coexist in a specific range of doping with the latter growing progressively at the expense of the former.