Optical properties of sputter-deposited cerium oxyfluoride thin films

Abstract
CeOxFy, films were made by reactive rf magnetron sputtering of Ce in Ar + O2 + CF4. Stoichiometries between CeO2 and CeO1.0F1.3 were obtained when the CF4 content lay between 0% and 9%. For wavelengths λ of >0.4 μm, the films were almost nonabsorbing, and the refractive index at λ = 0.55 μm went from 2.32 for CeO2 to 1.62 at 9% CF4. At λ < 0.4 μm and 4, the optical properties were consistent with an indirect band gap at 3.1–3.2 eV. CeO2 films could serve as intercalation hosts for Li+ ions.