AVS 45th International Symposium
    Surface Science Division Monday Sessions
       Session SS-MoP

Paper SS-MoP29
Electronic Promotion of Graphite Oxidation in the Presence of Cs Trapped between the Basal Planes

Monday, November 2, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: K.-Y. Kim, Pohang University of Science and Technology, South Korea
Authors: J.R. Hahn, Pohang University of Science and Technology, South Korea
K.-Y. Kim, Pohang University of Science and Technology, South Korea
H. Kang, Pohang University of Science and Technology, South Korea
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Oxidation of graphite is investigated by using scanning tunneling microscopy (STM) in the presence of Cs atom trapped between the carbon basal planes. Low energy (< 150 eV) bombardment of Cs@super +@ ions onto a graphite surface produces Cs interstitial defects (Cs-ID), where a Cs atom is trapped between the first and the second graphite layers. Oxygen adsorption onto the defected surface and the subsequent heating at 560 °C inside vacuum leads to formation of the pits with a depth of monolayer and a diameter of several nm. The pit formation starts from the Cs-ID's, indicating its promotion effect on the reaction with oxygen. The average diameter of the pit increases with the amount of supplied oxygen molecule. The experimental results suggest that a Cs-ID donates electron density to the neighboring carbon atoms, making the upper-layer carbons to be reactive with the oxygen molecule. The electron transfer from Cs-ID is the prevailing mechanism for the promoted oxidation, which is different from the direct mechanism proceeding via complex formation between the adsorbed Cs and the oxygen molecule, proposed from the previous studies of the oxidation of graphite covered with Cs.