Ternary, single-crystalline Bi2 (Te, Se)3 nanowires grown by electrodeposition

Abstract Single-crystalline, ternary n -type Bi 2 Te 3−y Se y nanowires are grown by potential-pulsed electrochemical deposition with 45 nm, 70 nm and 195 nm nominal diameters. Electrical conductivity and thermopower of the nanowires are measured. TEM analysis proves that the nanowires grow along the [110] direction with the c-axis perpendicular to the nanowire axis and yield diameters of 70–80 nm (nominally 45 nm, #1), 85–100 nm (70 nm, #2) and 265–325 nm (195 nm, #3). This yields electronic transport along the basal plane of the Bi 2 Te 3 crystal structure. Chemical composition of the nanowires is measured by TEM-EDX spectroscopy. These nanowires show exciting electronic properties, like Shubnikov-de-Haas oscillations at low temperatures, summarized in another paper. All nanowires investigated are oxygen contaminated but single crystalline, precipitates are only observed in #3 nanowire. The stoichiometry offset and fluctuations of #2 nanowire are significantly larger compared to #1 and #3 nanowires. The thermopower correlates with these structural data, the smallest thermopower is found for #2 nanowire and a similar, larger thermopower is found for #1 and #3 nanowires. For #1 and #2 nanowires dislocation densities of about 7.8 × 10 10 cm −2 and 1.0 × 10 11 cm −2 are observed, respectively, wherein dislocations lie parallel to the growth direction. While for #3 nanowire, a dislocation density of 1.2 × 10 10 cm −2 is observed and dislocations are oriented perpendicular to the growth direction. This reduces the heat conductivity of the #3 nanowire due to phonon scattering on the strain field of dislocations.