title: Hybridization of surface waves with organic adlayer librations: a helium atom scattering and density functional perturbation theory study of methyl-Si(111).
abstract: The interplay of the librations of a covalently bound organic adlayer with the lattice waves of an underlying semiconductor surface was characterized using helium atom scattering in conjunction with analysis by density functional perturbation theory. The Rayleigh wave dispersion relation of CH3- and CD3-terminated Si(111) surfaces was probed across the entire surface Brillouin zone by the use of inelastic helium atom time-of-flight experiments. The experimentally determined Rayleigh wave dispersion relations were in agreement with those predicted by density functional perturbation theory. The Rayleigh wave for the CH3- and CD3-terminated Si(111) surfaces exhibited a nonsinusoidal line shape, which can be attributed to the hybridization of overlayer librations with the vibrations of the underlying substrate. This combined synthetic, experimental, and theoretical effort clearly demonstrates the impact of hybridization between librations of the overlayer and the substrate lattice waves in determining the overall vibrational band structure of this complex interface.
authors.affiliation: The James Franck Institute and Department of Chemistry, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA.
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Brown
authors.affiliation: The James Franck Institute and Department of Chemistry, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA.
authors.forename: Zachary M
authors.initials: ZM
authors.lastname: Hund
authors.affiliation: Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via Cozzi 53, 20125 Milano, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Campi
authors.affiliation: Beckman Institute and Kavli Nanoscience Institute, Division of Chemistry and Chemical Engineering, 210 Noyes Laboratory, 127-72, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Leslie E
authors.initials: LE
authors.lastname: O'Leary
authors.affiliation: Beckman Institute and Kavli Nanoscience Institute, Division of Chemistry and Chemical Engineering, 210 Noyes Laboratory, 127-72, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Lewis
authors.affiliation: Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via Cozzi 53, 20125 Milano, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Bernasconi
authors.affiliation: Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via Cozzi 53, 20125 Milano, Italy and Donostia International Physics Center (DIPC), Universidad the País Vasco (EHU) 20018 Donostia/San Sebastian, Spain.
authors.forename: G
authors.initials: G
authors.lastname: Benedek
authors.affiliation: The James Franck Institute and Department of Chemistry, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Sibener