Optical constants of ZnO

The complex dielectric functions, epsilon(E) = epsilon(1)(E) + i epsilon(2)(E), of ZnO have been measured by spectroscopic ellipsometry (SE) in the photon-energy range between 1.5 and 5.0 eV at room temperature. The SE measurements are carried out on the surface parallel to the optic axis c, which allows the determination of the optical constants for light polarized perpendicular (E perpendicular to c) and parallel to the c-axis (E parallel to c). The measured SE spectra show the exciton peaks at similar to 3.4 eV (E-0 edge). These E(E) spectra are analyzed on the basis of a simplified model of the interband transitions. Excellent agreement is achieved between the calculated and experimental results over the entire range of photon energies. Dielectric-function-related optical constants, such as the complex refractive index n*(E) = n(E) + ik(E), absorption coefficient alpha(E) and normal-incidence reflectivity R(E), of ZnO have also been reported.