Approaching ideal graphene: The structure of hydrogen-intercalated   graphene on 6H-SiC(0001)
  We measure the adsorption height of hydrogen-intercalated quasi-free-standing monolayer graphene on the (0001) face of 6H silicon carbide by the normal incidence x-ray standing wave technique. A density functional calculation for the full ($6 \sqrt{3} \times 6 \sqrt{3}$)-R30$^\circ$ unit cell, based on a van der Waals corrected exchange correlation functional, finds a purely physisorptive adsorption height in excellent agreement with experiments, a very low buckling of the graphene layer, a very homogeneous electron density at the interface and the lowest known adsorption energy per atom for graphene on any substrate. A structural comparison to other graphenes suggests that hydrogen intercalated graphene on 6H-SiC(0001) approaches ideal graphene. 
J. Sforzini and L. Nemec and T. Denig and B. Stadtm\"uller and T.-L.   Lee and C. Kumpf and S. Soubatch and U. Starke and P....
cond-mat.mtrl-sci