Positiverole of Sn impurity on thermoelectric properties of Bi₂Te₃-based singlecrystals

M.K. Zhitinskaya¹, S. A. Nemov¹, M.Yu. Nikulina¹,T. E. Svechnikova², E. Müller³

¹StatePolitechnical University, St-Petersburg

²BaikovInstitute of Metallurgy and Materials Sciences, Moscow

³GermanAerospace Center (DLR), Institute of Materials Research, D-51170 Köln, Germany

An experimental studyon the influence of Sn doping on the thermal conductivity of Bi₂Te₃and Bi₂Te₃ with Te partially replaced by Se isreported. The thermoelectric properties: (thermal and electrical conductivity,Seebeck coefficient and its spatial distribution on the sample surface) of Bi₂Te₃-basedsingle crystals have been determined. The crystals were grown by Czochralskitechnique. The composition of samples is given by the chemical formula Bi_2-xSn_xTe_3-ySe_y.

Analysis of thermalconductivity has shown that the lattice thermal resistivity Wl is changing withthe amount of Sn impurity and with the type of an additional impurity. Thisfact is linked to the interaction of Sn impurity atoms with intrinsic defects.It was found that the maximum of Wl corresponds to a concentration of tin atomsc_Sn ~ (0.2 - 0.4) at%.

An increase by Snaddition of the homogeneity of the spatial concentration distribution wasdetected by measurements of the local Seebeck coefficient by a scanningthermo-probe.

The obtainedexperimental data support to the interpretation that the incorporation of Snatoms into Bi₂Te₃ and into Bi₂Te_3-xSe_x is accompanied by theformation of a band of resonant Sn-states against the background of the allowedvalence-band spectrum.