Vacuum ultraviolet dielectric function and band structure of ZnO

For ZnO, the optical dielectric functions for polarizations parallel and perpendicular to the optical axis were determined in the photon energy range from 4.0 to 9.5 eV by using generalized spectroscopic ellipsometry and the band structure was calculated by means of the empirical pseu-dopotential method. From the band structure, a theoretical dielectric function was derived. The dielectric functions reveal features that were identified as band-to-band transitions. The energies of those transitions were assigned to band-to-band transition energies of critical points of the calculated band structure.