Optical functions of Bi2Te3-Sb2Te3 solid solutions in the range of plasmon excitation and interband transitions

The spectra of the optical functions of Bi2Te3-Sb2Te3 solid solutions recorded in the range of 350–4000 cm−1 exhibited features caused by the response of free-carrier plasma and interband transitions forming the fundamental absorption edge in these materials. An increase in the Sb2Te3 percentage in the solid solution to 80% is accompanied by discontinuities of the functional dependences of the parameters characterizing plasma oscillations and a sharp increase in the optical band gap E g opt. The set of optical functions has been simulated in the adiabatic approximation taking into account the effect of plasmons and interband transitions and the general polarization background of the crystal. The results obtained make it possible to detail the pattern of change in the physical properties of Bi2Te3-Sb2Te3 solid solutions, which are of great practical importance for thermoelectric materials science.