Vibrational dynamics and band structure of methyl-terminated Ge(111)

Journal Article · Mon Sep 28 00:00:00 EDT 2015 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4931178· OSTI ID:22489654

Hund, Zachary M.; Nihill, Kevin J.; Campi, Davide; Bernasconi, M. ^[1]; Wong, Keith T.; Lewis, Nathan S. ^[2]; Benedek, G. ^[1]

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1. Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via Cozzi 53, 20125 Milano (Italy)
2. Division of Chemistry and Chemical Engineering, Beckman Institute and Kavli Nanoscience Institute, California Institute of Technology, 210 Noyes Laboratory, 127-72, Pasadena, California 91125 (United States)

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 CD{sub 3}-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 CH{sub 3}-Ge(111) and CH{sub 3}-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.

• OSTI ID: 22489654
• Journal Information: Journal of Chemical Physics, Vol. 143, Issue 12; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ATOMIC DISPLACEMENTS
ATOMS
BRILLOUIN ZONES
CRYSTALS
DEBYE-WALLER FACTOR
DENSITY FUNCTIONAL METHOD
DIFFRACTION
DISPERSION RELATIONS
DISPERSIONS
EXCITATION
HELIUM
HYBRIDIZATION
PERTURBATION THEORY
RAYLEIGH WAVES
SEMICONDUCTOR MATERIALS
SUBSTRATES
SURFACES
SYNTHESIS
THERMODYNAMIC PROPERTIES
TIME-OF-FLIGHT METHOD