Optical Properties of SnTe

The real ( ε 1 ) and imaginary ( ε 2 ) parts of the complex dielectric function, ε ( E )= ε 1 ( E )+ i ε 2 ( E ), of SnTe have been measured by spectroscopic ellipsometry (SE) in the 1.15-5.5 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 both the MDF and SCP models successfully explain the first-derivative spectra of ε ( E ) [ d ε ( E )/ d E ]. The MDF also shows excellent agreement with the experimental ε ( E ) spectra, but the SCP does not. Dielectric-related optical constants, such as the complex refractive index ( n * = n + i k ), absorption coefficient (α) and normal-incidence reflectivity ( R ), of SnTe are also presented.