Local layer-by-layer growth of Ni on hydrogen-terminated diamond C(111): A combined helium-atom scattering and XPS study

The growth, structure, and phonon dynamics of Ni islands deposited on H(1×1)C(111) was studied using high-resolution helium atom scattering and x-ray photoelectron spectroscopy. Depending on the amount of deposited nickel the islands formed at temperatures of 800 K are between 6- and 20-monolayers (ML) high and cover 50 to 85 % of the surface. Since the height distribution of these islands is very narrow a layer-resolved study of the phonon dynamics of these islands has been possible. For islands with a thickness of 6 ML an energy gap of 3 meV is observed at the center of the surface Brillouin zone corresponding to a vertical vibration of the whole Ni island with respect to the substrate. A lattice-dynamical analysis based on a rigid-substrate approximation indicates that force constant coupling of the Ni atoms to the surface amounts to only 15.75 N/m, suggesting only a weak metal-substrate interaction.