Bi2-xInxSe3crystals; optical properties and transport coefficients

Abstract

Single crystals of Bi_2-xIn_xSe₃ (x = 0.0-0.66) were prepared from the elements of 5N purity using the modified Bridgman method. On the samples with a various content of incorporated In-atoms the reflectivity in IR-region and the transport coefficients (electrical conductivity σ_⊥, Hall coefficient R_H (B ∥ c), Seebeck coefficient S_⊥) were measured. The results showed that the In-atoms incorporation to the crystal lattice of Bi₂Se₃ in the region of small concentrations of In-atoms increases the free carriers concentration, in the region of higher concentrations of In-atoms the free carriers concentration is suppressed. On the ground of measured changes in the values of transport coefficients and optical parameters (determined from the interpretation of infrared reflectivity) a model of point defects in the Bi_2-x In_x Se₃ crystal lattice has been suggested. This model takes into account the existence of antisite defects Bi'_Se in the Bi₂Se₃ crystal lattice the concentration of which is suppressed by incorporated In-atoms. The built-in In-atoms form uncharged defects In^x_Bi which are positively polarized.