Hydrogen termination of defects in graphene*

Defect introduction is one of the important strategies to tune the properties of graphene. Although, the number of defects is usually focused, and the chemical structure of defects has been not well considered in graphene. Actually, vacancies in graphene become magnetic depending on the number and position of termination hydrogen atoms. In this study, atomic vacancies are introduced into graphene as defects, and its hydrogen termination is investigated in order to clarify how chemical structure of vacancies affects graphene.
Atomic vacancies were introduced into the surface of graphite and epitaxial graphene grown on SiC as a model graphene by sputtering with Ar ion beam after pre-annealing. Adsorption of hydrogen molecules, atomic hydrogen and atmospheric exposure were performed on the sample. The Oxygen content is much smaller for the graphite surface exposed to atomic hydrogen and hydrogen molecules immediately after the defect introduction, compared with the samples exposed to air. This suggests we can control the termination atoms of defects by atmosphere after defects introduction to graphite surface.