Interfaces between graphene and double- or single-side fully hydrogenated graphene

The interfaces between graphene and either double- or single-side fully hydrogenated graphene (graphane or SSHG, respectively) are studied numerically to account for structural distortions induced by the interface. Graphene edges of zigzag, armchair, and bearded types are considered. The graphene/graphane interfaces with zigzag and armchair edges are shown to be robust with respect to hopping of hydrogen atoms from graphane to graphene. The energies of these interfaces are positive and increase linearly with the interface length, thus favoring flat boundaries and pointing to feasibility of graphene nanoribbons with atomically smooth edges within hydrogenated graphene. In the case of the bearded edge, the graphene/graphane interface appears to be unstable as its energy lowers upon hydrogen hopping across the interface. For the free standing SSHG, any kind of interface with graphene induces the binding of hydrogen atoms into diatomic molecules and their desorption. If both SSHG and graphene reside on a substrate, such instability is absent but the flat interfaces of graphene/SSHG are energetically unfavorable by the same token as for the bearded-type graphene/graphane interface.

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► Various interfaces between graphene and fully hydrogenated graphene are simulated.
► Positive interface tensions of graphene/graphane favor flat boundaries.
► The graphene/graphane interfaces with zigzag and armchair edges are stable.
► The graphene/graphane interface with the bearded edge is metastable.
► Interfaces between graphene and single-side hydrogenated graphene are unstable.