AVS 53rd International Symposium
    Surface Science Thursday Sessions
       Session SS-ThP

Paper SS-ThP18
Isotope Effect in Chemicurrent Experiments

Thursday, November 16, 2006, 5:30 pm, Room 3rd Floor Lobby

Session: Surface Science Poster Session
Presenter: D. Krix, University of Duisburg-Essen, Germany
Authors: D. Krix, University of Duisburg-Essen, Germany
R. Nuenthel, University of Duisburg-Essen, Germany
H. Nienhaus, University of Duisburg-Essen, Germany
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During exothermic reactions of atomic hydrogen or deuterium on a silver surface hot charge carriers are produced which have been observed by using Ag/Si(111) Schottky diodes. Thin film devices provide a means to bring a charge detector as close to the reaction site as the mean free path of the charge carriers. In the case of a p-doped substrate the Schottky barrier works as a high-pass energy filter for hot holes. We have therefore produced large area Schottky diodes with film thicknesses of up to 30 nm varying the thickness to rule out any influence of this device parameter. Those diodes were then exposed to beams of hydrogen atoms and deuterium atoms produced in a hot-capillary source. Gas exposures do not affect the Schottky barrier height significantly. While exposing the samples to defined atom fluxes the closed-loop current was monitored in real time. It shows that the current is proportional to the amount of flux supplied as long as the total flux is low and sticking is independent of hydrogen coverage. We have found hydrogen to generate more than three times the amount of hot holes than are created during reactions with deuterium. Theoretical predictions of non-adiabatic energy dissipation using the electronic friction model agree well with the experimental results.