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Optical properties of (Bi 1− x Sb x ) 2 Se 3 single crystals
Author(s) -
Navrátil J.,
Lošťák P.,
Drasar Č.,
Blachut T.
Publication year - 1996
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.2221940233
Subject(s) - analytical chemistry (journal) , absorption edge , materials science , permittivity , scattering , spectral line , crystal (programming language) , single crystal , dielectric , phonon , band gap , chemistry , optics , crystallography , condensed matter physics , physics , optoelectronics , chromatography , astronomy , computer science , programming language
(Bi 1− x Sb x ) 2 Se 3 ( x = 0 to 0.2) single crystals prepared from elements of 5N purity by means of a modified Bridgman method were characterized by measurements of infrared reflectance and transmittance. Values of the plasma resonance frequency ϵ p , optical relaxation time τ, and high‐frequency permittivity ϵ ∞ were determined by fitting the reflectance spectra. It was found that the substitution of Sb atoms for Bi atoms in the Bi 2 Se 3 crystal lattice leads to an increase in the ω p values, whereas in the range of higher Sb content the ω p values decrease. This effect is accounted for by a model of point defects in the crystal lattice of (Bi 1− x Sb x ) 2 Se 3 . The dependence of the absorption coefficient K on the energy of incident photons was determined from the transmittance spectra. The position of the short‐wavelength absorption edge is discussed. With regard to the longwavelength absorption edge it was found that the values of α in the relation K ∼ λ α lie in the interval 2.2 to 2.5, hence the dominant scattering mechanism of the free charge carriers in (Bi 1− x Sb x ) 2 Se 3 crystals at room temperature is the scattering by acoustic phonons.