Bismuth nanowire arrays: Synthesis and galvanomagnetic properties

This paper reports galvanomagnetic properties of arrays of single-crystal b ismuth nanowires, with diameters of 7 to 200 nm, embedded in an amorphous p orous anodic alumina matrix. A sample preparation technique is described th at makes it possible to obtain nanowires with diameters below 10 nm. The wi res are single crystals, with their long axes oriented in the bisectrix/tri gonal plane, about 19 degrees from the bisectrix axis. The temperature depe ndence (1.4 K less than or equal to T less than or equal to 300 K) of the e lectrical resistance, longitudinal magnetoresistance (0 T less than or equa l 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 transvers e 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 nanowir es are given. The results extend previous work to wires of narrower diamete r, and confirm the existence of the semimetal-semiconductor phase transitio n seen in the magnetoresistance. The data are discussed qualitatively in te rms of the interplay between the electron cyclotron radii, electron scatter ing on the wire walls, size-induced energy level quantization, and the tran sfer of carriers between the different carrier pockets of the Fermi surface . Nanowires of Bi are theoretically predicted to have a much higher thermoe lectric figure of merit than bulk Bi.