Surface States Transport in Topological Insulator \(\mathrm{Bi}_{0.83}\mathrm{Sb}_{0.17}\) Nanowires

We investigate the transport properties of topological insulator (TI) \(\mathrm {Bi}_{0.83}\mathrm {Sb}_{0.17}\) nanowires. Single-crystal nanowire samples with diameters ranging from 75 nm to 1.1 \(\mu \)m are prepared using high frequency liquid phase casting in a glass capillary; cylindrical single crystals with (10\(\bar{1}\)1) orientation along the wire axis are produced. \(\mathrm {Bi}_{0.83}\mathrm {Sb}_{0.17}\) is a narrow-gap semiconductor with an energy gap at the L point of the Brillouin zone, \(\Delta E = 21\) meV. The resistance of the samples increases with decreasing temperature, but a decrease in resistance is observed at low temperatures. This effect is a clear manifestation of TI properties (i.e., the presence of a highly conducting zone on the TI surface). When the diameter of the nanowire decreases, the energy gap \(\Delta E\) grows as 1 / d (for diameter \(d = 1.1 \upmu \)m and \(d =75\) nm \(\Delta E = 21\) and 45 meV, respectively), which proves the presence of the quantum size effect in these samples. We investigate the magnetoresistance of \(\mathrm {Bi}_{0.83}\mathrm {Sb}_{0.17}\) nanowires at various magnetic field orientations. Shubnikov-de Haas oscillations are observed in \(\mathrm {Bi}_{0.83}\mathrm {Sb}_{0.17}\) nanowires at \(T = 1.5\) K, demonstrating the existence of high mobility (\(\upmu _S = 26{,}700--47{,}000\) \(\mathrm {cm^2V^{-1}s^{-1}}\)) two-dimensional (2D) carriers in the surface areas of the nanowires, which are nearly perpendicular to the \(C_3\) axis. From the linear dependence of the nanowire conductance on nanowire diameter at \(T = 4.2\) K, the square resistance \(R_\mathrm{sq}\) of the surface states of the nanowires is obtained (\(R_\mathrm{sq} =70\) Ohm).