Dual Raman features of double coaxial carbon nanotubes with N-doped and B-doped multiwalls.

Double coaxial carbon nanotubes with nitrogen (N)-doped and boron (B)-doped multiwalls possess composite Raman characteristics, originating not only from the outer N-doped but also from inner B-doped layers. Both N and B dopings result in substantial shifts of the characteristic D band and G band of sp(2) carbon constituting nanotube walls but in different ways. The downshift of the G band is correlated with the decreases of electrical resistivity of carbon nanotubes regardless of N or B doping.