Thermoelectric and galvanomagnetic properties of bismuth chalcogenide nanostructured heteroepitaxial films

Hot wall technique was used to grow block single crystal films of Bi2Te3 and solid solutions of Bi0.5Sb1.5Te3 on mica (muscovite) substrates. X-ray diffraction studies demonstrated that the crystalline c-axis in the films was normal to the substrate plane. Seebeck coefficient, electrical conductivity and magnetoresistivity tensor components were measured at various orientations of magnetic and electric fields in the temperature interval 77–300 K. Scattering mechanism of charge carriers in the films was studied using temperature dependences of the degeneracy parameter and the Seebeck coefficient in terms of a many-valley model of energy spectrum. Obtained results have shown that the effective scattering parameter is considerably different from the value specific for an acoustic scattering of charge carriers in the weakly degenerate films due to an additional scattering of charge carriers on interface and interctystallite boundaries. These features of charge carrier scattering are supposed to affect electronic transport in the films and enhance figure of merit.