New atomic-scale features in graphite surfaces treated in a dielectric barrier discharge plasma

The effects of an air plasma generated by a dielectric barrier discharge (DBD) on highly oriented pyrolytic graphite (HOPG) have been investigated through scanning tunneling microscopy (STM), Raman and XPS spectroscopies. Three main types of nanometer/atomic scale features were identified by STM: (i) small bumps, attributed to surface atomic vacancies; (ii) smooth bumps, attributed to interstitial Ar or C atoms; and (iii) depressions not previously reported for graphite, and tentatively attributed to interstitial oxygen species. The evolution of the STM features suggests that the surface modification of HOPG by an air DBD plasma is dominated by physical processes (ion bombardment).