Growth and structures of monolayer and bilayer CeOx nanostructures on Au(111)

Abstract

The construction of well-defined CeOx/Au(111) model catalysts is key to the understanding of ceria-based catalysts or the Au–CeOx interface in catalytic reactions. Conventionally, owing to the Volmer–Weber growth of ceria on Au(111), ceria nanostructures with controlled layer thickness and well-defined structure have been difficult to grow on Au(111). We explored the influence of growth parameters, such as the substrate temperature for ceria deposition, the flux of Ce atoms and the annealing temperature in this study. We found that ceria prefers to form bilayer nanostructures, i.e. two OCe–O layers, over a large range of growth conditions, whereas monolayer ceria nanostructures could also be obtained on Au(111) with the careful control of growth kinetics. Upon the growth of these well-defined ceria nanostructures, element-specific STM images could also be achieved on their surfaces, which allow the identification of surface and sub-surface O vacancies on ceria. The construction and atomic-scale characterization of these CeOx/Au(111) model catalysts would facilitate the subsequent studies on their surface chemistry and aid our understanding on the catalysis by ceria nanostructures.