Improved electrical conductivity and power factor in Sn and Se co-doped melt-grown Bi₂Te₃ single crystal

In the current work, growth and thermoelectric characterization of tin and selenium co-doped single crystal bismuth telluride have been carried out in the range of temperature 10–400 K. The crystals show hexagonal crystal structure with R3 ¯ m space group. The direction of growth, quality of the single crystals, the density of dislocation, and dopants effect on the inner plane structure of the crystals have been analyzed through high-resolution X-ray diffraction study. Energy dispersive analysis of X-rays approves the elemental composition, and field emission scanning electron microscopy shows uniform growth with micro precipitates on the surface of the crystals. Quasi degenerate and non-degenerate electrical resistivity is observed in the pristine and doped samples, respectively. Temperature-dependent Seebeck coefficient measurements confirm the n-type semiconducting nature of the pristine as well as doped samples. Temperature-dependent power factor of (Bi_0.96Sn_0.04)₂Te_2.7Se_0.3 is found to increase by 1.1 times, and electrical resistivity reduced by 3.3 times as compared to pristine Bi₂Te₃.