3.2. Optical properties
The normal-incidence reflectance and transmittance spectra, in the wavelength range= 300–1200 nm, are shown in Fig. 3a. The transmittance spectra are obtained by dividing the measured transmittance by that of a fused silica substrate. The maximum transmittance of the film is higher than that of the substrate. This indicates that the cerium oxide films are optically inhomogeneous [6,12].