Thin films of cerium dioxide (CeO2) were deposited by atomic layer deposition (ALD) at 250 °C on both Si and titanium nitride (TiN) substrates. The ALD growth produces CeO2 films with polycrystalline cubic phase on both substrates. However, the films show a preferential orientation along crystallographic direction for CeO2/Si or for CeO2/TiN, as revealed by X-ray diffraction. Additionally, CeO2 films differ in the interface roughness depending on the substrate. Furthermore, the relative concentration of Ce3 + is 22.0% in CeO2/Si and around 18% in CeO2/TiN, as obtained by X-ray photoelectron spectroscopy (XPS). Such values indicate a ~ 10% off-stoichiometry and are indicative of the presence of oxygen vacancies in the films. Nonetheless, CeO2 bandgap energy and refractive index at 550 nm are 3.54 ± 0.63 eV and 2.3 for CeO2/Si, and 3.63 ± 0.18 eV and 2.4 for CeO2/TiN, respectively. Our results …