Growth and Morphology of Ceria on Ruthenium (0001)

Abstract

Cerium oxide plays an important role in catalysis due to its prominent ability to store, transport, and release oxygen. Inverse model catalysts have attracted strong interest since their study promises a better understanding of the basic fundamentals of catalysis, but still a lot remains unknown about their structure and morphology. Here, we present an extensive growth and morphology study of the inverse catalyst model system ceria on Ru(0001) by applying spectroscopic photoemission and low-energy electron microscopy. Triangular three-dimensional islands of ceria were grown by depositing cerium metal in an oxygen ambient. We were able to control the island size, nucleation density, and oxidation state by choosing appropriate growth conditions. For highly oxidized ceria, we observe a commensurate (7 × 7) diffraction pattern, demonstrating that the oxide–metal interface is well-ordered. Furthermore, two distinct types of cerium oxide rotational domains are identified, whose quantity, average azimuthal alignment, and distribution with respect to the principle directions of the substrate lattice strongly depend on the growth conditions. Together, these findings are expected to have a high impact on the catalytic behavior of the model system.