Optical Properties of Single-Crystal Anatase TiO₂

Polarized Reflection spectra of single-crystal anatase TiO₂ were measured in a photon energy range from 2 to 25 eV using synchrotron orbital radiation. Dielectric constants and absorption spectra were obtained from reflection spectra by Kramers-Kronig transformations. To interpret the structures that were observed in the spectra, the electronic states of anatase were calculated by using a cluster model with a size of Ti₅O₁₄. The structures observed in the energy region from 3 to 12 eV can be identified primarily due to the transition from O(2p) orbitals to Ti(3d) ones. The polarization dependence of the spectra in the above energy region is also effectively exhibited by the calculations from this model. The vague structures in the higher energy region (>12 eV) which can be clearly distinguished in spectra from the low energy part are due to the transition from O(2p) orbitals to Ti(4s, 4p) ones.