Transport coefficients and defect structure of Sb2−Ag Te3 single crystals

Abstract

Abstract Incorporation of Ag in the crystal lattice of Sb 2 Te 3 creates structural defects that have a strong influence on the transport properties. Single crystals of Sb 2− x Ag x Te 3 ( x =0.0; 0.014; 0.018 and 0.022) were characterized by measurements of the temperature dependence of the electrical resistivity, Hall coefficient, Seebeck coefficient and thermal conductivity in the temperature range of 5–300 K. With an increasing content of Ag the electrical resistance, the Hall coefficient and the Seebeck coefficient all decrease. This implies that the incorporation of Ag atoms in the Sb 2 Te 3 crystal structure results in an increasing concentration of holes. However, the doping efficiency of Ag appears to be only about 50% of the expected value. We explain this discrepancy by a model based on the interaction of Ag impurity with the native defects in the Sb 2− x Ag x Te 3 crystal lattice. Defects have a particularly strong influence on the thermal conductivity. We analyze the temperature dependence of the lattice thermal conductivity in the context of the Debye model. Of the various phonon scattering contributions, the dominant influence of Ag incorporation in the crystal lattice of Sb 2 Te 3 is revealed to be point-defect scattering where both the mass defect and elastic strain play a pivotal role.