The Shubnikov-de Haas effect and thermoelectric properties of Tl-doped Sb2Te3 and Bi2Se3

The influence of doping with Tl on the Shubnikov-de Haas effect at T = 4.2 K in magnetic fields up to 38 T in p-Sb2-x Tl (x) Te-3 (x = 0, 0.005, 0.015, and 0.05) and n-Bi2-x Tl (x) Se-3 (x = 0, 0.01, 0.02, 0.04, and 0.06) single crystals is investigated. Extreme cross-sections of the Fermi surface in both materials decrease upon doping with Tl: the hole concentration decreases in Sb2-x Tl (x) Te-3 due to the donor effect of Tl and the electron concentration in n-Bi2-x Tl (x) Se-3 decreases due to the acceptor effect of Tl. The temperature dependences of the Seebeck coefficient, electrical conductivity, thermal conductivity, and dimensionless thermoelectric figure of merit in a temperature range of 77-300 K are measured. The thermal conductivity and electrical conductivity decrease upon doping with Tl both in p-Sb2-x Tl (x) Te-3 and in n-Bi2-x Tl (x) Se-3. The Seebeck coefficient increases in all compositions upon an increase in doping over the entire measured temperature range. The thermoelectric figure of merit increases upon doping with Tl.