Electrical transport properties of single crystal rarehyphen;earth sesquisulfides

摘要

Electrical transport properties of semiconducting single crystal Nd2S3, Gd2S3, and Dy2S3(Th3P4, bcc structure) have been investigated between 80 and 300deg;K. Electrical resistivity (rgr;), Hall coefficient (RH), and thermoelectric power (agr;), all measured as a function of temperature, are reported for several singlehyphen;crystal samples of each compound. The crystals are black degeneratenhyphen;type semiconductors owing to slight excess rare earth over R2S3stoichiometry. To interpret the data over this temperature range where the samples display extrinsic semiconducting behavior, we have considered a parabolic band model combined with different scattering mechanisms. The scattering mechanisms include acoustical phonon scattering, alloy scattering, and charged impurity scattering. Above 150deg;K for the Nd2S3samples and above 200deg;K for the Gd2S3and Dy2S3samples, the data seem to suggest that a parabolic band model with alloy scattering appears possible. These conclusions appear reasonable in light of the known excess rare earth found in each sample investigated having the Th3P4defect structure.