Defect-induced oxidation of graphite

Atomic vacancies with controlled depth and size are generated on a graphite surface by low-energy ion bombardment. The reactivity of vacancies towards an oxygen molecule is investigated by using scanning tunneling microscopy (STM) and density functional theory. An oxygen molecule (i) exothermally dissociates and then chemisorbs at the top sites and/or the bridge sites of a vacancy, or (ii) forms a precursor state of molecular oxygen at a bridge site. Reaction pathways for oxidative etching are proposed to interpret serpentine and circular etching patterns observed by STM.