ICT2014 Abstracts

While the stoichiometrically prepared Bi₂Te₃ single crystals often exhibit hole-dominated conduction as a result of the Bi_Te-type antisite defects, doping by indium progressively changes the electrical conduction of Bi_2-xIn_xTe₃ (x = 0 − 0.30) single crystals from p-type (0 ≤ x ≤ 0.10) to n-type (0.20 ≤ x ≤ 0.30). This is observed via measurements of both the Hall effect and the Seebeck coefficient performed in the (0001) basal plane in the temperature range of 2 − 300 K. At low levels of In, 0 ≤ x ≤ 0.10, the temperature dependent in-plane electrical resistivity maintains its metallic character as the density of holes decreases. Heavier In content x = 0.20 drives the electrical resistivity into a prominent non-metallic regime displaying the weak anti-localization (WAL) type of magnetoresistance at the lowest temperatures. At the highest concentration of x = 0.30, the samples revert back into the metallic state with electron dominated conduction. Thermal conductivity measurements of Bi_2-xIn_xTe₃ single crystals, as examined by the Debye-Callaway phonon conductivity model, reveal a generally stronger point defect scattering of phonons with the increasing In content. The systematic evolution of transport properties suggests that the Fermi level of Bi₂Te_3, which initially lies in the valence band (for x = 0), gradually shifts toward the top of the valence band (for 0.01 ≤ x ≤ 0.10), then moves into the band gap (for x = 0.20), and eventually intersects the conduction band (for x = 0.30).

This work is supported by the Center for Solar and Thermal Energy Conversion, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0000957.