Atomically Smooth\nFully Hydroxylated CeO<sub>2</sub>(001) Films on YSZ(001)

CeO<sub>2</sub> is an important support material with\nredox properties\ninteresting for heterogeneous catalysis and energy conversion applications.\nHere, we present a facile growth procedure for epitaxial CeO<sub>2</sub>(001) thin films supported by YSZ(001) suitable for combined catalytic\nactivity and structural investigations. The growth of the CeO<sub>2</sub> thin films was performed using standard ultrahigh-vacuum\n(UHV) preparation techniques followed by tube furnace annealing in\nair. Thorough characterization prior to and after the tube furnace\nannealing revealed that this step induces significant restructuring\nof the film. Complete characterization by atomic force microscopy\n(AFM), X-ray reflectivity (XRR), grazing incidence X-ray diffraction\n(GIXRD), cross-section high-resolution scanning tunneling electron\nmicroscopy (HR-STEM), X-ray photoemission spectroscopy (XPS), and\npolarization-resolved infrared reflection absorption spectroscopy\n(IRRAS) showed that the film is fully oxidized and atomically smooth\nwith a coherent crystal lattice over the full film thickness. A dislocation\nnetwork at the CeO<sub>2</sub>/YSZ interface compensates the lattice\nmismatch between film and the YSZ support, yielding a film with bulk\nlattice parameters. The bulk terminated surface is found to be defect\nfree with negligible amount of adsorption sites and stabilized by\nthe presence of hydroxyl groups for polarity compensation.