Stabilization of the ceria ι-phase (Ce7O12) surface on Si(111)

In this work a 250 nm CeO2(111) film grown on a hex-Pr2O3(0001)/Si(111) system is annealed at 660 °C for 30 min to form the ι bulk phase of Ce7O12 as controlled by x-ray photoelectron spectroscopy. The (111) surface of the stabilized ι phase is characterized via high-resolution low-energy electron diffraction. The ι-phase surface exhibits a (7×7)R19.1° superstructure with two mirror domains. This structure is attributed to a periodic ordering of oxygen vacancies compared to the fluorite structure of CeO2.