Doping dependence of the G-band Raman spectra of an individual multiwall carbon nanotube

We present a gate-dependent Raman spectroscopy and electric transport measurements of an individually connected multiwall carbon nanotube in the field-effect transistor configuration at room temperature. We discuss the origin of the four distinct sharp modes in the G-band feature. The overall G-band is blueshifted by tuning the Fermi level under a back-gate voltage. Each mode experiences different energy shifts symmetrical for n and p doping. Assuming that the four peaks can be tentatively assigned to four different shells of the multiwall carbon nanotube, we propose a simple quantitative analysis which unravels intershell charge transfer within the nanotube.