IR Transmission Investigations of (Bi1−xSbx)2Te3Single Crystals

Abstract
IR transmission spectra are measured at (Bi1−xSbx)2Te3single crystals withx= 0.5, 0.7, 0.9 near the absorption edge at 84 and 300 K. For the determination of the optical constants also the reflectivity of polarized infrared light is recorded in the plasma range at 300 K. The dependence of the free carrier part of the dielectric function on the wave number ϵ(v̄) indicates that acoustic phonon scattering is the dominant mechanism. The interband contribution ϵ(v̄) is interpreted by indirect allowed band transitions. The energy gap and the phonon energies are calculated andlie in a physically reasonable range.