Parameters of Fundamental Optical Functions and Elementary Transition Bands for Mg2X Compounds (X = Si, Ge, Sn)

• Published in: Journal of applied spectroscopy Vol. 88; no. 1; pp. 137 - 145
• Main Authors: Sobolev, V. Val, Kalugin, A. I., Antonov, E. A.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.03.2021; Springer Nature B.V
• Subjects: Analytical Chemistry; Atomic/Molecular Structure and Spectra; Excitons; Germanium; Integrals; Lattice parameters; Mathematical analysis; Physics; Physics and Astronomy; Silicon compounds; Spectra; Tin; interband transition; volume electron energy losses; exciton; Si; combined Argand diagram; Mg; Sn; Kramers–Kronig relations; Ge; optical function; dielectric constant
• ISSN: 0021-9037; 1573-8647
• DOI: 10.1007/s10812-021-01152-0

The spectra of 16 optical functions of the group of compounds Mg 2 X (X=Si, Ge, Sn) in the range of 1–11 eV at 77 K were determined and compared. Their main features and general relationships were established. Calculations were performed on the basis of the experimental reflectance spectra R(E) using the Kramers–Kronig relations and analytical formulas connecting the optical functions. The integral spectra of the imaginary part of the dielectric function ε 2 (E) were broken down into elementary transition bands in the region of 1.5–6.0 eV using the improved nonparametric method of combined Argand diagrams with allowance for the effective number of valence electrons forming the individual elementary bands. For Mg 2 X compounds (X = Si, Ge, Sn), instead of 5–6 maxima and steps, an average of six times more elementary components of transitions caused by exciton and interband transitions were found in the integral spectra. The energies of the maxima and the areas of the selected elementary components of the transition bands of the three compounds were determined and compared. The supposed nature and localization of the identified elementary components of the transitions are proposed on the basis of known theoretical calculations. The dependence of the energies of the maxima of the selected transition bands on the lattice parameters of the three compounds is plotted.