Morphology, Stoichiometry, and Interface Structure of CeO2 Ultrathin Films on Pt(111)

Studies of model systems based on cerium oxide are important to improve current understanding of the properties of ceria-based materials, which find wide application based on the ability of cerium oxide to store, release, and transport oxygen. We report a study of CeO2 ultrathin films grown on the Pt(111) surface by reactive deposition of Ce using molecular or atomic oxygen as the oxidizing gas. High-temperature treatments in O2 allowed us to obtain epitaxial structures with a very good quality in terms of morphology, stoichiometry, and structure. The cerium oxide films have a very flat morphology with terraces several tens of nanometers wide. The stoichiometry of the films is mainly CeO2, and the concentration of Ce3+ ions in the film can be reversibly increased by temperature treatments. We propose that the Pt substrate oxidation has a determinant role for the epitaxial stabilization of ceria films.