Temperature-Dependent Reduction of Epitaxial Ce1-xPrxO2-δ (x=0-1) Thin Films on Si(111): A Combined Temperature-Programmed Desorption, X-ray Diffraction, X-ray Photoelectron Spectroscopy, and Raman Study

The inherent properties of epitaxial oxide thin-film layers have attracted the intense interest of different research fields, such as catalysis and microelectronics. The focus of this work is the temperature-dependent oxygen release, oxygen vacancy formation, and lattice rearrangement of Ce1-xPrxO2-delta thin films with systematic stoichiometry variation (x = 0-1) and oxygen deficiency (delta > 0) on Si(111). The mixed oxide layers were heteroepitaxially grown by coevaporating molecular beam epitaxy. To observe the oxygen release, temperature-programmed desorption was performed. Furthermore, laboratory-based X-ray diffraction measurements were carried out after several annealing steps to investigate the crystal structure rearrangement. The contribution of Ce4+/Ce3+ and Pr4+/Pr3+ redox systems to the oxygen release and lattice rearrangement was clarified by X-ray photoelectron spectroscopy. Finally, Raman spectroscopy was performed to detect structural defects in the oxide lattice (i.e., oxygen vacancies and MO8-complexes) and their temperature dependence, which thus provides microscopic insights into the atomic oxygen release mechanism. The oxygen-releasing temperature and the oxygen storage capacity in such Ce1-xPrxO2-delta model thin films can be engineered by the Pr concentration.