We present a study of electronic transport in individual Bi nanowires of large diameter relative to the Fermi wavelength. Measurements of the resistance and thermopower of intrinsic and Sn-doped Bi wires with various wire diameters, ranging from 150 to 480 nm, have been carried out over a wide range of temperatures ͑4 -300 K͒ and magnetic fields ͑0-14 T͒. We find that the thermopower of intrinsic Bi wires in this diameter range is positive ͑type p͒ below about 150 K, displaying a peak at around 40 K. In comparison, intrinsic bulk Bi is type n. Magnetothermopower effects due to the decrease of surface scattering when the cyclotron diameter is less than the wire diameter are demonstrated. The measurements are interpreted in terms of a model of diffusive thermopower, where the mobility limitations posed by hole-boundary scattering are much less severe than those due to electron-boundary scattering.

We present measurements of Shubnikov-de Haas oscillations in arrays of bismuth nanowires. For 80-nm wires, the hole concentration is less than 30% of that for bulk Bi, a finding that is consistent with current models of quantum confinement effects. However, 30-nm-diameter nanowires, which are predicted to be semiconductors, show a nearly isotropic short period of 0.025 T -1 , consistent with a heavy carrier concentration five times that of bulk Bi. These results are discussed in terms of surface-induced charge carriers in a spherical Fermi surface pocket that are uniformly distributed in the 30-nm nanowire volume and that inhibit the semimetal-tosemiconductor transition.

The 240–620nm diameter nanowires were freely suspended and thermopower measurements were carried out over the temperature range 4–300K and for stresses as high as 1GPa. The peaks of up to 80μV∕K that are observed around 40K are interpreted in terms of a model of diffusion thermopower under strong electron and hole-boundary scattering. The partial Seebeck coefficients are calculated from the stress-dependent carrier Fermi energies obtained from magnetoresistance measurements. The prospect of Bi nanowire arrays achieving high thermoelectric figure of merit is discussed.