Properties of composite BxCyNz nanotubes and related heterojunctions

We review the stability and electronic properties of composite B_xC_yN_z nanotubes, including BN-, BC₂N- and B-doped carbon nanotubes. We show in particular that BC₂N systems are driven towards the segregation of pure C and BN sections. The same process of segregation into BC₃ islands is evidenced in the case of B-doped carbon nanotubes. These spontaneous segregation processes lead to the formation of quantum dots or nanotube heterojunctions with potential important technological applications.