Theoretical investigation of thermoelectric transport properties of cylindrical Bi nanowires

We report here a theoretical model for the transport properties of cylindrical Bi nanowires. Based on the band structure of Bi nanowires and the semiclassical transport model, the thermoelectric figure of merit $Z_{1\mathrm{D}}T$ is calculated for Bi nanowires with various wire diameters and wire orientations. The results show the trigonal axis is the most favorable wire orientation for thermoelectric applications, and $Z_{1\mathrm{D}}T>\mathrm{}1\mathrm{}$ is predicted for n-type trigonal wires with diameters $d_w<10\mathrm{}$ nm. The effect of the T-point holes on $Z_{1\mathrm{D}}T$ is also investigated. It is found that $Z_{1\mathrm{D}}T$ can be significantly enhanced, especially for p-type Bi nanowires, if the T-point holes are removed or suppressed.