Comparisons of electrical/magneto-transport properties of degenerate semiconductors BiCuXO (X=S, Se and Te) and their electron-phonon-interaction evolution

Layered BiCuXO (X=S, Se, and Te) compounds attract much attention recently because of their superior thermoelectric properties. However, the major shortcoming of these compounds is the relatively large electrical resistance. Exploring the mechanism of electrical scattering of BiCuXO can give some hints on how to optimize their electrical conductivity. Here, we compared electrical and magnetotransport properties of degenerate semiconductor BiCuXO. These compounds show metallic electrical properties, and the in-plane resistivity is linearly dependent on the temperature at the high-temperature regime (>150K). The magnetoresistance of these compounds is approximately quadratically dependent on the square of magnetic field B, and magnetoresistance decreases from 10%-16% to 0.5% when the temperature is increased from 2 to 300K. The Hall measurements substantiate that the electrical carriers of BiCuXO are holes, which perhaps come from Bi vacancies. The electron-optical-phonon interaction is the major mechanism of electron scattering when the temperature is higher than 80K. Analyzing the linear coefficient rho(xx)-T of BiCuXO (X=S, Se, and Te) suggests that the averaged electron-phonon interaction of BiCuSO is nearly six times larger than that of BiCuSeO/BiCuTeO. Based on the Thomas-Fermi model, compared with BiCuSO, the weak electron-phonon interaction in BiCuSeO/BiCuTeO could be attributed to a highly screened Coulomb interaction between electrons and ions. This work may be useful to optimize the electrical properties of BiCuXO to satisfy the requirement of thermoelectric materials.