Enhancement of thermoelectric figure of merit in bismuth nanotubes

Thermoelectric transport properties of bismuth nanotubes are theoretically predicted and mechanisms of the enhancement of the thermoelectric figure of merit (ZT) are discussed. A significant enhancement in ZT was found and is mainly attributed to the enhanced Seebeck coefficient resulting from the modified density of state and decreased phonon thermal conductivity induced by the boundary phonon scattering in nanotubes. The optimum power factor can be realized at the Fermi energy level locating near the subband edge, and the optimal ZT increases with decreasing the thickness and diameter of nanotubes.