First-principles investigations on the dielectric and infrared reflectance spectra of the II-VI binary chalcogenides.

The phonon, dielectric, and infrared reflectance spectra of the II-VI binary chalcogenides with wurtzite structure are carefully investigated using the first-principle linear response theory. The impact of sulfur group elements from S to Te on various characteristics of binary chalcogenides is examined. The results indicate that the phonon vibrational frequencies are influenced by the relative atomic mass. The overall permittivities are primarily determined by the electronic polarization. When Born effective charge approaches the nominal ionic charge, the compounds exhibit ionicity. The modal-oscillator strengths of the chalcogenides decrease from top to bottom within the same group of elements corresponding to an increase in relative atomic mass. In binary chalcogenides having the identical cation, the resonance absorption peaks experience a frequency decrease when the anions' mass increases. The infrared reflection spectrum shows red-shifts with decreasing electronegativity of the anions. The reststrahlen band-widths of the infrared optical mode are impacted by the splitting of LO/TO. [ABSTRACT FROM AUTHOR]