Optical Properties of Cu_<b>2</b>O Studied by Spectroscopic Ellipsometry

Abstract

The real ( ε 1 ) and imaginary ( ε 2 ) parts of the dielectric function of Cu 2 O have been measured by spectroscopic ellipsometry in the 1.2–5.2 eV photon-energy range at room temperature. The Cu 2 O 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 0 C ∼2.6 eV ("blue" exciton series), E 0 D ∼2.8 eV ("indigo" exciton series), E 1 A ∼3.5 eV and E 1 B ∼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 + i k ), absorption coefficient (α) and normal-incidence reflectivity ( R ), of Cu 2 O are also presented. Also, we obtain the static and high-frequency dielectric constants of Cu 2 O as ε s =7.87 and ε ∞ =6.95, respectively.