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Investigation of the Valence Band Structure of Thermoelectric (Bi 1− x Sb x ) 2 Te 3 Single Crystals
Author(s) -
Stordeur M.,
Stölzer M.,
Sobotta H.,
Riede V.
Publication year - 1988
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221500120
Subject(s) - seebeck coefficient , anisotropy , effective mass (spring–mass system) , condensed matter physics , valence (chemistry) , electrical resistivity and conductivity , hall effect , phonon , scattering , electronic band structure , materials science , dielectric , density of states , thermoelectric effect , chemistry , optics , physics , organic chemistry , optoelectronics , thermodynamics , quantum mechanics
Abstract Using combined optical‐spectroscopic and transport investigations it is succeeded for the first time to determine all relevant valence band data for the whole series of mixed crystals (Bi 1− x Sb x ) 2 Te 3 (0 ≦ x ≦ 1). The reflectivity of polarized infrared light including its anisotropy is measured in the wave number range of 300 to 4000 cm −‐1 . In addition to the spectra the Hall coefficients ϱ 123 and ϱ 312 , the electrical conductivity σ ⟂ c , and the Seebeck coefficient S ⟂ c are also given. In term of a six‐valley band model and scattering by acoustical phonons all experimental data are consistently described. The main axis masses m ii H , the ellipsoid tilt angle ϑ, the effective density‐of‐states mass m d , and the susceptibility masses m ⟂ (χ) ,∥ c are calculated in dependence on composition, also the Fermi level E F , the carrier density p , the mobility μ ⟂ c , the high frequency dielectric constant ϵ ∞ ⟂,∥ c , and the relaxation time τ opt . For the first time the structure factors in the Hall coefficients are given. In the plot m ( x ) the distinct maxima of m 22 Hand m d near x = 0.8 are evident and important for the application of these substances.