DIELECTRIC PROPERTIES AND ELECTRICAL CONDUCTIVITY OF POLYCRYSTALLINE Bi2Te3-Bi2Sb3 FILMS IN A MICROWAVE FIELD AND UNDER MECHANICAL DEFORMATION

The results of a study of the dielectric and electrical properties of polycrystalline films of a Bi₂Te₃ ‒ Bi₂Sb₃ solid solution under the influence of a microwave field and mechanical deformation are presented in order to determine the mechanisms of influence of point and extended inhomogeneities. The spectra of dielectric permittivity depending on the composition, temperature dependences of the specific conductivity and impedance of films under uniaxial static deformation are considered. The detected microwave and deformation phenomena in polycrystalline films are qualitatively analyzed based on the effective medium model. It is shown that the infrared spectra of dielectric permittivity ( , ), electrical conductivity ( , ) and absorption coefficient of a solid solution (Bi_xSb_1‒x)₂Te₃, depending on the value 0 < x < 0.5, and deformations are correlated. Moreover, the theoretical values in the field of photon energy are somewhat lower than the experimental ones, and the opposite situation occurs. Threshold frequency values with characteristic maxima in the impurity absorption region associated with collective excitations of the electron-plasma interaction are observed in all spectra. It has been experimentally established that for freshly prepared films, under the influence of moderate tensile strain, the impedance dependence on temperature undergoes a radical change with deformation up to at the same temperature and only metallic conductivity is observed, and then the sign of the temperature coefficient of the impedance g(e) inverts in the temperature range. The critical values of the Tc temperature and their difference decrease with an increase in the value of e. During deformations, a condition occurs and the falling section of the curve disappears. The strain sensitivity of films in the microwave field strongly depends on the temperature and time of thermal treatment, and at a temperature of about Т »  500 K and a time of about t » 2‒3hours, it acquires the mostoptimalandstablevalues.

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