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 1D 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 1D TϾ1 is predicted for n-type trigonal wires with diameters d w Ͻ10 nm. The effect of the T-point holes on Z 1D T is also investigated. It is found that Z 1D T can be significantly enhanced, especially for p-type Bi nanowires, if the T-point holes are removed or suppressed.

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A theoretical model based on the basic electronic band structure of bulk Bi is developed to predict the dependence of the band structure and thermoelectric properties on nanowire width. By carefully tailoring the Bi wire size and carrier concentration, substantial enhancement in the thermoelectric figure of merit is expected for small nanowire widths.