Growth, Structure, and Stability of Ag on CeO2(111): Synchrotron Radiation Photoemission Studies

Abstract

The growth and interfacial electronic properties of Ag on CeO2(111) thin films have been studied by synchrotron radiation photoemission spectroscopy (SRPES), low energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). Stoichiometric CeO2(111) thin films were grown on a Ru(0001) substrate. Ag grows as three-dimensional (3D) particles on the well-ordered CeO2(111) surface at 300 K with a number density of ∼1 × 1012 particles/cm2. When the CeO2(111) surface has a high density of defects, Ag initially populates these defect sites, leading to a two-dimensional (2D) island growth at low coverages followed by 3D islanding at high coverages. The binding energy of Ag 3d increases when the Ag particle size decreases, which is mainly attributed to the final-state screening. No strong interaction between Ag and CeO2(111) is found. The CeO2(111) surface is slightly reduced upon Ag deposition, which can be ascribed to the reverse spillover of oxygen atoms from the Ag−CeO2 boundary to the Ag nanoparticles. The Ag particles on CeO2(111) experience significant sintering when the temperature increases before they desorb from the surface.