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 °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 O₂. Such all electron charge transfer mechanism is more probable for promoted oxidation than a direct interaction between Cs and O₂. Deformation of the surface layer by a Cs-ID enhances the production of large pits.