Bismuth nanowire arrays: Synthesis and galvanomagnetic properties

This paper reports galvanomagnetic properties of arrays of single-crystal bismuth nanowires, with diameters of 7 to 200 nm, embedded in an amorphous porous anodic alumina matrix. A sample preparation technique is described that makes it possible to obtain nanowires with diameters below 10 nm. The wires are single crystals, with their long axes oriented in the bisectrix/trigonal plane, about 19 degrees from the bisectrix axis. The temperature dependence (1.4 K less than or equal to T less than or equal to 300 K) of the electrical resistance, longitudinal magnetoresistance (0 T less than or equal to B less than or equal to 5 T with 1.4 less than or equal to T less than or equal to 75 K, and 0T less than or equal to B less than or equal to 1 T with 80 less than or equal to T less than or equal to 300 K) and transverse magnetoresistance (0 T less than or equal to B less than or equal to 5 T with 1.4 less than or equal to T less than or equal to 75 K) of the nanowires are given. The results extend previous work to wires of narrower diameter, and confirm the existence of the semimetal-semiconductor phase transition seen in the magnetoresistance. The data are discussed qualitatively in terms of the interplay between the electron cyclotron radii, electron scattering on the wire walls, size-induced energy level quantization, and the transfer of carriers between the different carrier pockets of the Fermi surface. Nanowires of Bi are theoretically predicted to have a much higher thermoelectric figure of merit than bulk Bi.