Intercalation-etching of graphene on Pt(111) in H2 and O2 observed by in-situ low energy electron microscopy

Abstract

Graphene layers are often exposed to gaseous environments in their synthesis and application processes, and interactions of graphene surfaces with molecules particularly H2 and O2 are of great importance in their physico-chemical properties. In this work, etching of graphene overlayers on Pt(111) in H2 and O2 atmospheres were investigated by in-situ low energy electron microscopy. Significant graphene etching was observed in 10-5 Torr H2 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 O2 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 O2 and H2 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.