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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
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.