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Schlagwörter:
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Zusammenfassung:
Three experimental methods enable us to study solid surfaces on the atomic
scale:
1. Electron Microscopy can achieve atomic resolution in both transmission and
reflection modes under special conditions, producing promising results. However,
surface studies are hampered by bad vacuum conditions in most instruments.
2. Scanning Tunneling Microscopy has caused wide spread interest due to the
experimental simplicity. Not only have a great number of structural problems been solved, tunneling spectroscopy also reveals electronic surface properties.
3. Field ion microscopic techniques display atomic surface structures, allow experiments with single atoms and can identify the chemical nature of single atoms or molecules and their binding energies.Pulse techniques are used for kinetic measurements and determination of intermediates in heterogeneous catalysis. Cluster-ions with low internal energy can be field desorbed. The disadvantage of this method is that samples have to drawn into tips and high electrostatic fields have to be applied.
Examples are given to show how field ion microscopy can determine surface structure
bond direction and surface reconstruction, and how the surface motion of individual
Particles,can be measured and used to derive fundamental thermodynamic data,
(Ni+CO→Ni((CO)4) and insensitive reactions (decomposition of methanol) are observed. Photon-stimulated field desorption is applied to study properties of cluster ions.
