Dresden 2009 – scientific programme
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O: Fachverband Oberflächenphysik
O 56: Metal substrates: Epitaxy, growth and adsorbates
O 56.3: Talk
Thursday, March 26, 2009, 15:30–15:45, SCH A316
Non adiabatic processes during homoepitaxy of silver and gold films — •Domocos Kovacs1, Eckart Hasselbrink2, and Detlef Diesing2 — 1Institut für Experimentalphysik, Universität Duisburg Essen — 2Institut für Physikalische Chemie, Universität Duisburg Essen
Thin film metal-insulator-metal (MIM) tunnel junctions have been employed in the last years in the investigation of electronic excitations induced by particles at metal surfaces. Such type of junctions act simultaneously as target and detector: While the electronic excitation is produced by the irradiation of the top metal layer, the excited charge carriers (electrons and holes) are detected in the bottom metal layer as an internal emission current. A major advantage offered by the present method in comparison with the methods measuring the external emission is the possibility of detecting excited charge carriers of very low energy (< 5 eV). We show that a MIM junction is suitable for the investigation of the electronic effects accompanying the adsorption of metal atoms from the gas phase onto the surface of a metal film consisting of the same atomic species. Thus, we show that the adsorption of Au(Ag) Atoms at the surface of the top Au(Ag) film of a Au(Ag)-TaOx-Ta tunnel junction generates hot charge carriers which are finally detected in the bottom Ta film. The relatively large emission yield, of the order of 10−4 electrons per incident atom, measured for 15-20 nm Au(Ag) films, indicates that the binding energy of 3-4 eV/atom, released during adsorption, is primarily transferred into the electronic system.