ISBN 9783843930772

978-3-8439-3077-2, Reihe Physik

Ivan Baev
The Electronic Structure of Small Mass Selected Clusters as Probed by Substrate Band Structure and Molecules

146 Seiten, Dissertation Universität Hamburg (2017), Softcover, A5

Zusammenfassung / Abstract

The scale up of matter: from atoms to large solids is the field of cluster physics. Especially in the small size limit, where the amount of surface atoms in a cluster is comparable to the amount of bulk atoms, quantum size effects play a huge but yet unpredictable role. These unpredictable quantum size effects can govern important observable macroscopic properties such as: color, resistivity, magnetism and chemical reactivity which are important for applications in everyday life.

This thesis addresses the interplay of two extremes: atomic and solid state physics. Atomically small clusters, containing iron, rhodium or iron and rhodium as a “nano-alloy” were deposited in dilute quantities on a clean, crystalline copper substrate. The effect of the deposited clusters is measured in terms of substrate band structure. The results show the evolution of the electronic structure as a function of cluster size. This evolution turns out to depend non-monotonic on the amount of iron or rhodium atoms and therefore forms a considerable benchmark for theoretical calculations in this field.

It turns out that the copper 3d-bands are strongly affected by the deposited clusters, thus implying a significant role of d-d electron interaction. Because the copper d-bands are fully occupied and located 2-4 eV below the Fermi level the question, about how the copper d-band electrons are actually affected, arises.

Furthermore, the chemical reactivity of the deposited clusters is tested towards oxidation with oxygen and subsequent reaction upon thermal activation and carbon monoxide dosage. These results are linked to the measured electronic structures of the pristine systems. Such analyses could potentially lead to highly efficient catalysts consisting of abundant elements.

Although the copper surface is generally considered a weakly interacting among the 3d transition metals, the measurements show the significance of d-band interaction. In an approach to reduce the cluster-substrate interaction a more insulating surface is considered: Cu2N on Cu(100). The investigations address the feasibility of a large scale Cu2N array and show the core level electronic structure, which serves as a fingerprint of the chemical environment, as function of annealing temperature and initial nitrogen dose.