Optical properties of Cu2O studied by spectroscopic ellipsometry

The real (epsilon(1)) and imaginary (epsilon(2)) parts of the dielectric function of Cu2O have been measured by spectroscopic ellipsometry in the 1.2-5.2eV photon-energy range at room temperature. The Cu2O single crystals used in this study were grown by a floating-zone melting technique. Dielectric-function spectra measured reveal distinct structures at energies of E-0C similar to 2.6 eV ("blue" exciton series), E-0D similar to 2.8 eV ("indigo" exciton series): E-1A similar to 3.5 eV and E-1B similar to 4.3 eV. The spectra are analyzed on the basis of a simplified model of the interband transitions. Results are in satisfactory agreement with the experimental data over the entire range of photon energies. Dielectric-related optical constants, such as the complex refractive index (n* = n + ik), absorption coefficient (alpha) and normal-incidence reflectivity (R): of Cu2O are also presented. Also. we obtain the static and high-frequency dielectric constants of Cu2O as epsilon(s) = 7.87 and epsilon(infinity) = 6.95, respectively.