Optical Constants of ZnO

The complex dielectric functions, ε ( E )= ε 1 ( E )+ i ε 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 ⊥ c ) and parallel to the c -axis ( E // c ). The measured SE spectra show the exciton peaks at ∼3.4 eV ( E 0 edge). These ε ( 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 )+ i k ( E ), absorption coefficient α( E ) and normal-incidence reflectivity R ( E ), of ZnO have also been reported.