Optical properties of single-crystal rutile RuO₂ and IrO₂ in the range 0.5 to 9.5 eV

We have measured the near-normal incidence reflectivity of single-crystal rutile RuO₂ and IrO₂ for E⃗∥c axis and E⃗⊥c axis at room temperature in the photon energy range 0.5-9.5 eV. From a Kramers-Kronig analysis of the reflectivity we have obtained the spectral dependence of the real and imaginary parts of the complex dielectric constant (ε₁ and ε₂, respectively) and refractive index (n and k, respectively) for each material. Comparison with recent band-structure and density-of-states calculations and past experimental studies of related solids has enabled us to gain further insight into the nature of the oxygen p electrons and metal d electrons in these materials.