Stable C-atom displacements on HOPG surface under plasma low-energy argon-ion bombardment

Surface defects are generated by an Ar plasma on crystalline graphite. In situ scanning tunneling microscopy reveals localized defects surrounded by a R30degrees superstructure (Friedel's charge oscillations) for short treatment times and long-range disordered lattices for longer treatment times. In situ X-ray photoelectron spectroscopy C 1s core-level spectra exhibit a broadening attributed to a distribution of C atoms in inequivalent sites. As implantation of heteroatoms and formation of vacancies can be ruled out, defects are attributed to stable displaced surface carbon atoms.