Promoted graphite oxidation in the presence of Cs trapped between basal planes

Graphite surface oxidation promoted by cesium interstitial defects (Cs-IDs) has been investigated using scanning tunneling microscopy. Bombardment with low energy Cs+ ions (<100 eV) primarily produces Cs-IDs by trapping Cs between the top two graphite layers. Oxygen adsorption on the defected surface, and subsequent heating of the sample to 560 degrees C, leads to the formation of large pits at a monolayer depth and several nanometers in diameter. The pit formation starts from the Cs-IDs. The experimental results suggest that a Cs-ID donates electron charge to the surrounding carbon atoms, promoting the upper-layer to be reactive with O-2. Such an electron charge transfer mechanism is more probable for promoted oxidation than a direct interaction between Cs and O-2. Deformation of the surface layer by a Cs-ID enhances the production of large pits. (C) 1999 Elsevier Science B.V. All rights reserved.