Surface States Transport in Topological Insulator Nanowires

We investigate the transport properties of topological insulator (TI) Bi0.83Sb0.17 nanowires. Single-crystal nanowire samples with diameters ranging from 75 nm to 1.1 μm are prepared using high frequency liquid phase casting in a glass capillary; cylindrical single crystals with (101̄1) orientation along the wire axis are produced. Bi0.83Sb0.17 is a narrow-gap semiconductor with an energy gap at the L point of the Brillouin zone, 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 E grows as 1/d (for diameter d = 1.1μm and d = 75 nm E = 21 and 45 meV, respectively), which proves the presence of the quantum size effect in these samples. We investigate the magnetoresistance of Bi0.83Sb0.17 nanowires at various magnetic field orientations. Shubnikov-de Haas oscillations are observed in Bi0.83Sb0.17 nanowires at T = 1.5 K, demonstrating the existence of high mobility (μS = 26,700−−47,000 cm2V−1s−1) two-dimensional (2D) carriers in the surface areas of the nanowires, which are nearly perpendicular to theC3 axis. From the linear dependence of the nanowire conductance on nanowire diameter at T = 4.2 K, the square resistance Rsq of the surface states of the nanowires is obtained (Rsq = 70 Ohm). B L. A. Konopko [email protected] 1 Ghitu Institute of Electronic Engineering and Nanotechnologies, 2028 Chisinau, Moldova 2 International Laboratory of High Magnetic Fields and Low Temperatures, 53-421 Wroclaw, Poland 3 Department of Chemistry, Howard University, Washington, DC 20059, USA 4 LPMN, École Polytechnique Fédérale de Lausanne EPFL, 1015 Lausanne, Switzerland