title: Vibrational dynamics and band structure of methyl-terminated Ge(111).
abstract: A combined synthesis, experiment, and theory approach, using elastic and inelastic helium atom scattering along with ab initio density functional perturbation theory, has been used to investigate the vibrational dynamics and band structure of a recently synthesized organic-functionalized semiconductor interface. Specifically, the thermal properties and lattice dynamics of the underlying Ge(111) semiconductor crystal in the presence of a commensurate (1 × 1) methyl adlayer were defined for atomically flat methylated Ge(111) surfaces. The mean-square atomic displacements were evaluated by analysis of the thermal attenuation of the elastic He diffraction intensities using the Debye-Waller model, revealing an interface with hybrid characteristics. The methyl adlayer vibrational modes are coupled with the Ge(111) substrate, resulting in significantly softer in-plane motion relative to rigid motion in the surface normal. Inelastic helium time-of-flight measurements revealed the excitations of the Rayleigh wave across the surface Brillouin zone, and such measurements were in agreement with the dispersion curves that were produced using density functional perturbation theory. The dispersion relations for H-Ge(111) indicated that a deviation in energy and lineshape for the Rayleigh wave was present along the nearest-neighbor direction. The effects of mass loading, as determined by calculations for CD3-Ge(111), as well as by force constants, were less significant than the hybridization between the Rayleigh wave and methyl adlayer librations. The presence of mutually similar hybridization effects for CH3-Ge(111) and CH3-Si(111) surfaces extends the understanding of the relationship between the vibrational dynamics and the band structure of various semiconductor surfaces that have been functionalized with organic overlayers.
authors.affiliation: The James Franck Institute and Department of Chemistry, The University of Chicago, 929 E. 57 Street, Chicago, Illinois 60637, USA.
authors.forename: Zachary M
authors.initials: ZM
authors.lastname: Hund
authors.affiliation: The James Franck Institute and Department of Chemistry, The University of Chicago, 929 E. 57 Street, Chicago, Illinois 60637, USA.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Nihill
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: Division of Chemistry and Chemical Engineering, Beckman Institute and Kavli Nanoscience Institute, California Institute of Technology, 210 Noyes Laboratory, 127-72, Pasadena, California 91125, USA.
authors.forename: Keith T
authors.initials: KT
authors.lastname: Wong
authors.affiliation: Division of Chemistry and Chemical Engineering, Beckman Institute and Kavli Nanoscience Institute, California Institute of Technology, 210 Noyes Laboratory, 127-72, 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.
authors.forename: G
authors.initials: G
authors.lastname: Benedek
authors.affiliation: The James Franck Institute and Department of Chemistry, The University of Chicago, 929 E. 57 Street, Chicago, Illinois 60637, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Sibener