Vacancy ordering in ultrathin copper oxide films on Cu(111)

Zhu, B. and Huang, W. and Lin, H. and Feng, H. and Palotás, Krisztián and Lv, J. and Ren, Y. and Ouyang, R. and Yang, F. (2024) Vacancy ordering in ultrathin copper oxide films on Cu(111). JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 146 (23). pp. 15887-15896. ISSN 0002-7863

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Abstract

Oxide thin films grown on metal surfaces have wide applications in catalysis and beyond owing to their unique surface structures compared to their bulk counterparts. Despite extensive studies, the atomic structures of copper surface oxides on Cu(111), commonly referred to as “44” and “29”, have remained elusive. In this work, we demonstrated an approach for the structural determination of oxide surfaces using element-specific scanning tunneling microscopy (STM) imaging enhanced by functionalized tips. This approach enabled us to resolve the atomic structures of “44” and “29” surface oxides, which were further corroborated by noncontact atomic force microscopy (nc-AFM) measurements and Monte Carlo (MC) simulations. The stoichiometry of the “44” and “29” frameworks was identified as Cu23O16 and Cu16O11, respectively. Contrary to the conventional hypothesis, we observed ordered Cu vacancies within the “44” structure manifesting as peanut-shaped cavities in the hexagonal lattice. Similarly, a combination of Cu and O vacancies within the “29” structure leads to bean-shaped cavities within the pentagonal lattice. Our study has thus resolved the decades-long controversy on the atomic structures of “44” and “29” surface oxides, advancing our understanding of copper oxidation processes and introducing a robust framework for the analysis of complex oxide surfaces.

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