Somephysical properties of Hf-doped-Sb₂Te₃ single crystals

T.Plechácek¹, J. Navrátil¹, P. Hájek²,A. Krejcová², P. Losták²

¹Joint Laboratory ofSolid State Chemistry of Institute of Macromolecular Chemistry of the Academyof Sciences of the Czech Republic and University of Pardubice,Studentská 84, 53210 Pardubice, Czech Republic

²Facultyof Chemical Technology, University of Pardubice, Čs. Legií Square565, 532 10 Pardubice, Czech Republic

Single crystals ofHf-doped Sb₂Te₃ (c_Hf = 0-2.4x10¹⁹cm^-3) were prepared from the elements of Sb, Hf and Te of the 5Npurity by a modified Bridgman method. The obtained crystals were characterizedby the measurements of the reflectivity R in the plasma resonance frequencyregion. Values of the plasma resonance frequency, w_p, were determined by fitting thereflectance spectra using the relations for the real and imaginary parts of thecomplex dielectric function, following from the Drude-Zener theory. From theobserved changes in the value w_p it was concluded that the doping of Hf-atoms into thecrystal structure of Sb₂Te₃ results in a decrease in theconcentration of free current carriers - holes. This conclusion was confirmedby the measurement of temperature dependencies of the Hall coefficient R_H,electrical conductivity s and the Seebeck coefficient a, within the temperature range of 100-400 K.Moreover, temperature dependences of the power factor sa² and mobility m~(R_H.s) of free carriers are discussed.