Atomic Scale STM Imaging of Alloy Surfaces With Chemical Resolution

Abstract

The surface structure formation and the activity of alloy surfaces in (electro-)catalysis strongly depend on the interaction and order of the atoms in the bulk and on the surface, and thus knowledge of the exact position and chemical identity of individual atoms is of fundamental interest. Scanning tunneling microscopy (STM) imaging allows for real space imaging of ordered and especially disordered alloy surfaces, providing insights in the exact position of different atoms by means of chemical resolution, which were and are not accessible with other surface science techniques. In order to understand STM imaging with chemical resolution, in this work first the fundamental experimental aspects and theoretical concepts of STM imaging are summarized. Focusing on STM imaging on an atomic scale level of alloy surfaces, different concepts which would allow for the differentiation of different types of atoms are discussed. The relevance of STM imaging with chemical resolution of alloy surfaces is finally presented on some selected examples from the literature, with respect to structure formation and the structure–activity relationship in (electro-)catalysis. Finally, some current experimental and technical limitations in STM imaging with chemical resolution are summarized.