Optical Properties of PbTe

Abstract

The real ( ε 1 ) and imaginary ( ε 2 ) parts of the dielectric function, ε ( E )= ε 1 ( E )+ i ε 2 ( E ), of PbTe have been measured by spectroscopic ellipsometry (SE) in the 1.15–5.4 eV photon-energy range at room temperature. The measured SE spectra reveal distinct structures at energies of E 1 , E 2 and E 3 critical points. These data are analyzed using two theoretical models, namely, the model dielectric function (MDF) and standard critical-point (SCP) model. It is found that the SCP model can provide a satisfactory fit to the second derivatives of ε ( E ) spectra [ d 2 ε ( E )/ d E 2 ], but does not yield good fits to ε ( E ) spectra. The MDF, on the other hand, results in excellent agreement with the experimental data for both ε ( E ) spectra and their derivatives. Dielectric-related optical constants, such as the complex refractive index ( n * = n + i k ), absorption coefficient (α) and normal-incidence reflectivity ( R ), of PbTe are also presented.