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Abstract: We use low-energy electron microscopy to investigate how graphene is removedfrom Ru0001 and Ir111 by reaction with oxygen. We find two mechanisms onRu0001. At short times, oxygen reacts with carbon monomers on the surroundingRu surface, decreasing their concentration below the equilibrium value. Thisundersaturation causes a flux of carbon from graphene to the monomer gas. Inthis initial mechanism, graphene is etched at a rate that is given precisely bythe same non-linear dependence on carbon monomer concentration that governsgrowth. Thus, during both growth and etching, carbon attaches and detaches tographene as clusters of several carbon atoms. At later times, etchingaccelerates. We present evidence that this process involves intercalatedoxygen, which destabilizes graphene. On Ir, this mechanism creates observableholes. It also occurs mostly quickly near wrinkles in the graphene islands,depends on the orientation of the graphene with respect to the Ir substrate,and, in contrast to the first mechanism, can increase the density of carbonmonomers. We also observe that both layers of bilayer graphene islands on Iretch together, not sequentially.

Autor: Elena Starodub, Norman C. Bartelt, Kevin F. McCarty

Fuente: https://arxiv.org/

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