Thermopower Measurements of Pure and Sn (Te) Doped Bismuth Nanowires*

Theoretical work based on one-dimensional (1D) models indicates that Bi wires with diameter smaller than 50 nm can exhibit superior thermoelectric properties since the density of states at the Fermi level of a 1D system can be tuned to very high values. Also, recently, angle-resolved photoemission spectroscopy (ARPES) studies of Bi thin films have shown that Bi nanowires support Rashba spin-orbit surface states, with high carrier densities of around$5\times 10^{12}cm^{-2}$, that are hybridized with ``bulklike'' electrons and holes, a phenomenon that has not been considered in current models of Bi nanowires. We carried out an experimental study of the transport properties and thermopower of bismuth nanowire arrays (NWA) with wire diameters ranging between 60 nm and 13 nm at temperatures ranging between 4 K and 300 K, for magnetic fields of up to 1 T. Both pure bismuth and doped Bi were studied. The results are interpreted in a multicarrier diffusion thermopower model.