The phonon dispersion of graphene on Ir(111) has been determined by means of angle-resolved inelastic electron scattering and density functional calculations. Kohn anomalies of the highest optical-phonon branches are observed at the¯ andK point of the surface Brillouin zone. AtK the Kohn anomaly is weaker than observed for pristine graphene and graphite. This observation is rationalized in terms of a decrease of the electron-phonon coupling due to screening of graphene electron correlations by the metal substrate.

Phthalocyanine molecules have been adsorbed to Ir(111) and to graphene on Ir(111). From a comparison of scanning tunneling microscopy images of individual molecules adsorbed to the different surfaces alone it is difficult to discern potential differences in the molecular adsorption geometry. In contrast, vibrational spectroscopy using inelastic electron scattering unequivocally hints at strong molecule deformations on Ir(111) and at a planar adsorption geometry on graphene. The spectroscopic evidence for the different adsorption configurations is supported by density functional calculations.

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The phonon dispersion of singly oriented graphene on Ir(111) has been determined by angle-resolved inelastic electron scattering. Replica of graphene phonon branches are induced by the moiré superstructure. Calculations for a linear chain of C atoms attached to an infinitely heavy substrate reveal that imposing a superstructure by periodically varying the C-C interaction and the C-substrate coupling induces replicated phonons at wave vectors reflecting the supercell periodicity. Deviations between the phonon dispersions of graphene on Ir(111) and of pristine graphene are analyzed and rationalized in terms of the weak graphene-Ir(111) interaction.

Spectroscopic signatures of vibrational excitations on initially oxidized Be(0001) are identified by a combination of electron energy loss spectroscopy and density functional calculations. Prominent spectral features are due to vibrations in a Be-O mixing layer. Scanning tunneling microscopy indicates that initial oxidation occurs locally in the form of islands. The acoustic surface plasmon persists on the oxygen-covered surface. Its dispersion has been determined along the¯ K direction and is virtually identical to the dispersion of the acoustic surface plasmon of the clean surface.