Temperature-dependent reduction of epitaxial Ce_{1- x}Pr _xO_2-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 Ce _1-xPr_xO_2-δ thin films with systematic stoichiometry variation (x = 0-1) and oxygen deficiency (δ > 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⁺/Ce ³⁺ 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 Ce_1-xPr _xO_2-δ model thin films can be engineered by the Pr concentration.