Phase separation of hydrogen atoms adsorbed on graphene and the   smoothness of the graphene-graphane interface
  The electronic properties of a graphene sheet with attached hydrogen atoms is studied using a modified Falicov-Kimball model on the honeycomb lattice. It is shown that in the ground state this system separates into two phases: fully hydrogenated graphene (graphane) and hydrogen-free graphene. The graphene-graphane boundary acquires a positive interface tension. Therefore, the graphene-graphane interface becomes a straight line, slightly rippled by thermal fluctuations. A smooth interface may be useful for the fabrication of mesoscopic graphene-based devices. 
A.L. Rakhmanov, A.V. Rozhkov, A.O. Sboychakov, Franco Nori
cond-mat.mes-hall