▎ 摘　　要

The structure and the low-energy phonon dispersion of graphene (Gr) on Ni(111) have been experimentally investigated with helium atom scattering (HAS). The Rayleigh mode observed for Gr/Ni(111) is almost identical to the one measured on clean Ni(111). The energy of the flexural ZA mode at the (Gamma) over tilde point was found to be similar to 20 meV, significantly lower than the value predicted by recent DFT calculations. The HAS diffraction spectra reveal that the graphene layer has a three-fold symmetry, with a lattice constant a (2.48 +/- 0.02) angstrom and shows an effective step-defect scattering reduction when the Ni(111) is covered with a graphene sheet. Gr/Ni(111) surface is a very efficient and inert mirror for He atoms, with a specular reflectivity of ca. 20%. The predominant role of inelastic scattering in Gr/Ni(111) is revealed by analysis of the diffraction spectra background and Debye-Waller measurements. (C) 2015 Elsevier Ltd. All rights reserved.