Growth mode and oxidation state analysis of individual cerium oxide islands on Ru(0001)

The growth of cerium oxide on Ru(0001) by reactive molecular beam epitaxy has been investigated using low-energy electron microscopy (LEEM) and diffraction as well as local valence band photoemission. The oxide islands are found to adopt a carpet-like growth mode, which depending on the local substrate morphology and misorientation leads to deviations from the otherwise almost perfect equilateral shape at a growth temperature of 850°C. Furthermore, although even at this high growth temperature the micron-sized CeO2(111) islands are found to exhibit different lattice registries with respect to the hexagonal substrate, the combination of dark-field LEEM and local intensity-voltage analysis reveals that the oxidation state of the islands is homogeneous down to the 10nm scale. •Cerium oxide is grown on ruthenium inside a low-energy electron microscope (LEEM).•The identified carpet growth mode is shown to determine the oxide island shape.•Intensity-voltage LEEM is demonstrated to be sensitive to oxidation state changes.•The oxidation state is found to be laterally homogeneous on the nanometer scale.•Ceria islands of the same oxidation state may have different substrate registries.