Abstract
Interlayer surface defects and thermoelectric properties in layered films of n-Bi2Te2.7Se0.15S0.15 topological insulators L. N. Lukyanova*, O. A. Usov, M. P. Volkov, V. A. Rusakov Ioffe Institute Russian academy of science, 194021 St.Petersburg, Russia *E-mail: lidia.lukyanova@mail.ioffe.ru Abstract In layered films of n-Bi2Te2.7Se0.15S0.15 topological insulators optimized for temperatures below room temperature, the morphology of the (0001) interlayer surface and thermoelectric properties were studied. On the profiles of the (0001) surface, we identified neutral impurity defects arising from the substitution of Se and S atoms for Te atoms and donor antisite defects of tellurium at bismuth sites, which affect the thermoelectric properties. The average value of thermoelectric figure of merit in n-Bi2Te2.7Se0.15S0.15 films increases to <Z> ≈ 3.0•10-3 K-1 in the range 80 – 215 K, while in bulk solid solution <Z> ≈ 2.0•10-3 K-1. An increase in the thermoelectric figure of merit in films is associated with an increase in the energy dependence of the relaxation time due to an increase in the effective scattering parameter reff. It is shown that in films the Seebeck coefficient, the density of states effective mass m/m0, and the material parameter proportional to the power factor increase, while the lattice κL and electronic thermal conductivity κe decrease, which determines the increase in thermoelectric figure of merit.
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