Atomically Smooth Fully Hydroxylated CeO2(001) Films on YSZ(001)

Abstract

CeO₂ is an important support material with redox properties interesting for heterogeneous catalysis and energy conversion applications. Here, we present a facile growth procedure for epitaxial CeO₂(001) thin films supported by YSZ(001) suitable for combined catalytic activity and structural investigations. The growth of the CeO₂ thin films was performed using standard ultrahigh-vacuum (UHV) preparation techniques followed by tube furnace annealing in air. Thorough characterization prior to and after the tube furnace annealing revealed that this step induces significant restructuring of the film. Complete characterization by atomic force microscopy (AFM), X-ray reflectivity (XRR), grazing incidence X-ray diffraction (GIXRD), cross-section high-resolution scanning tunneling electron microscopy (HR-STEM), X-ray photoemission spectroscopy (XPS), and polarization-resolved infrared reflection absorption spectroscopy (IRRAS) showed that the film is fully oxidized and atomically smooth with a coherent crystal lattice over the full film thickness. A dislocation network at the CeO₂/YSZ interface compensates the lattice mismatch between film and the YSZ support, yielding a film with bulk lattice parameters. The bulk terminated surface is found to be defect free with negligible amount of adsorption sites and stabilized by the presence of hydroxyl groups for polarity compensation.