| Abstract: | Graphene layers are often exposed to gaseous environments in their synthesis and application processes, and interactions of graphene surfaces with molecules particularly H_2 and O_2 are of great importance in their physico-chemical properties. In this work, etching of graphene overlayers on Pt(111) in H_2 and O_2 atmospheres were investigated by in-situ low energy electron microscopy. Significant graphene etching was observed in 10~(-5) Torr H_2 above 1023 K, which occurs simultaneously at graphene island edges and interiors with a determined reaction barrier at 5.7 eV. The similar etching phenomena were found in 10.7 Torr O_2 above 973 K, while only island edges were reacted between 823 and 923 K. We suggest that etching of graphene edges is facilitated by Pt-aided hydrogenation or oxidation of edge carbon atoms while intercalation-etching is attributed to etching at the interiors at high temperatures. The different findings with etching in O_2 and H_2 depend on competitive adsorption, desorption, and diffusion processes of O and H atoms on Pt surface, as well as intercalation at the graphene/Pt interface. |
