The Nernst-Ettingshausen, Seebeck, and Hall effects in Sb2Te3 single crystals

This paper reports on measurement of the temperature dependences of the following transport coefficients: electrical conductivity in the σ11 cleavage plane, the Seebeck coefficients S11 and S33 (axis 3 is along the trigonal crystal axis), the Hall coefficients R123 and R321, and the Nernst-Ettingshausen constant Q123; all measurements were made on high-quality Czochralski-grown Sb2Te3 single crystals. The results obtained are analyzed in terms of phenomenological theory. It is shown that the main features of the experimental data, including the anisotropy of the Hall and Seebeck effects, can be explained within a two-band model with notice-ably different anisotropy of the mobilities of holes of two types in the cleavage-plane and trigonal-axis directions. Estimates are made of the band-gap width (ɛg≅0.3 eV), as well as of the energy gap between the main and additional valence-band extrema (Δɛv∼0.1 eV).