Gunther Andersson

Abstract:

Metal clusters have unique properties that change with the type and number of atoms that form the cluster. Metal clusters typically consist of less than about 100 atoms, are atomically precise and thus have specific size and shape. As a consequence of this, clusters also have discrete, individual electron energy levels, which i) differ from the levels in the constituting individual atoms and ii) depend on the number of atoms in the cluster. Due to their unique, size-dependent electronic properties, some metal clusters have been termed "superatoms" and can be considered as the 3rd dimension of the Periodic Table. Conceptually, the ability to control the size and energy levels of a metal cluster is ideal for modifying semiconductor surfaces, however, to date this is a rather challenging subject. Depositing metal clusters onto semiconductor surfaces allows the modification of the electronic properties and chemical composition of the semiconductor surface precisely and independently from the properties of the bulk material. In the present work we are using mainly ligand-protected, chemically made metal clusters. Cluster modified surfaces have potential in catalysis applications which could lead to harvesting solar energy and converting into fuels. For analysing all stages of the process of depositing clusters onto semiconductor surfaces electron spectroscopy techniques (X-ray photoelectron spectroscopy (XPS)), scanning techniques (atomic force microscopy (AFM)) and microscopy (scanning) transmission electron microscopy (STEM and TEM) have been employed. Subsequent to deposition also the electronic and conformational structure have been analysed because these are the two properties which are believed to play the crucial role in catalysis. Metastable induced electron spectroscopy (MIES) has been used for determining the electronic structure of deposited clusters. Results of photocatalytic reactions will be shown.