Optical properties and electronic structure of ZnO crystal in a wide energy range of intrinsic absorption. I. The fundamental optical functions spectra

Five variants of full sets of the fundamental polarized optical functions of ZnO crystal were determined in the energy range of 0-26 eV for E perpendicular to c and E parallel to c polarizations from the experimental reflectivity spectra reported in three different papers and the theoretical dielectric permittivity spectra given in two different papers. The calculations were performed using the integral Kramers-Kronig relations and the analytical formulas relating the functions to each other. The main features and parameters of the five variants of the optical functions spectra were established. Their peculiarities were discussed using the theoretical calculations of bands, energy values of interband transition maxima, and their localization in the Brillouin zone, as well as the experimental spectra of dielectric permittivity, electron energy losses, and photoemission.