Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 93: Surface Chemical Reactions

O 93.3: Talk

Friday, February 29, 2008, 10:45–11:00, MA 043

Dissociation of oxygen on Ag(100) by electron induced manipulation — •Carsten Sprodowski, Michael Mehlhorn, and Karina Morgenstern — Institut für Festkörperphysik, Abteilung Oberflächen, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover, Germany

Low-temperature scanning tunneling microscopy is used to study oxygen dissociation on Ag(100). Deposition of oxygen on Ag(100) at 80K leads to small clusters of 1 to 10 molecules. Inelastic electron tunnelling manipulation is used for the manipulation of these molecules. Thereby the STM tip is set above them, the feedback loop of the STM is switched off and a voltage is applied between tip and sample for exciting the electronical states of the molecules. For small energies (1500meV with 0.3 nA) the cluster reorders, while above a distinct energy threshold the electron induced manipulation leads to a dissociation of the single molecules within the cluster. After manipulation in some cases dissociated pairs at different distances are found. However mostly only one atom of the dissociated molecule is observed. During the dissociation the tunnelling current rises until a plateau of 5nA (3500mV) and remains there for some milliseconds. One possible explanation is a vertical orientation of the molecules as a metastable state before dissociating. In addition atomic resolution and a dissociated cluster during the same scan let us identify the adsorbate places of the dissociated atoms.