Strong polaronic effects on rutile TiO2 electronic band edges

Abstract

Thin TiO2 films are prepared by dc magnetron sputtering as well as by the sol-gel technique, and the optical band edge absorption α(ω) is obtained from transmission spectroscopy. The electronic structure and optical properties are studied employing a first-principle linearized augmented plane-wave method within the local density approximation (LDA), improved by an on-site Coulomb self-interaction potential (LDA+USIC). We show that the correction potential, the polaronic screening, and the spin-orbit interaction are crucial for determining the TiO2 effective electron and hole masses. The dielectric function ε(ω)=ε1(ω)+iε2(ω) and the high-frequency constantε(0⪡ω⪡Eg∕ℏ) show pronounced anisotropy. The electron-optical phonon interaction affectsε(ω≈0) strongly.