Poster

Structural and dynamical properties of methylated Ge(111) surface

D. Campi¹, Z. H. Hund², K. Nihill², K.Wong³, N. S. Lewis³, M. Bernasconi¹, G. Benedek^1,4, and S. J. Sibener²

¹Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via Cozzi 53, 20125 Milano, Italy

²The James Franck Institute and Department of Chemistry, The University of Chicago, 929 E. 57th Street, Chicago, Illinois 60637, USA

³Beckman Institute and Kavli Nanoscience Institute, Division of Chemistry and Chemical Engineering, 210 Noyes Laboratory, 127-72, California Institute of Technology, Pasadena, California 91125, USA

⁴Donostia International Physics Center (DIPC), University of the Basque Country (UPV-EHU), Paseo M. de Lardizabal 4, 20018 San Sebastián/Donostia, Spain

Germanium has recently attracted a renewed interest for application in electronic devices due to its superior carrier mobility with respect to silicon and the need to substitute in ultrascaled architectures high-k dielectrics for silicon oxide, which is so far the major reason for using Si instead of Ge. A complete and ordered passivisation of the germanium surface by organic adlayers has recently been achieved [1] enlarging the possible technological applications of this material. The vibrational features of methyl-terminated germanium surfaces impact the thermal properties and the ability of the surface to accommodate energy. By combining helium atom scattering spectroscopy (HAS) with density functional perturbation theory (DFPT) we investigated the surface structure and phonon dispersion relations for the CH3 passivated Ge(111)(1×1) surface. This study allows for a characterization of the interactions between the low energy vibrations of the adsorbate and the lattice waves of the underlying substrate, as well as of the interactions between neighboring methyl groups, across the entire momentum-resolved vibrational energy spectrum. As a comparison we also performed DFPT calculations on the CD3-Ge(111)-(1×1) and H-Ge(111)(1×1) surfaces and the hydrogenated and methylated germanium single layer (germanane and methylated germanane).

[1] D. Knapp, B. S. Brunschwig, and N. S. Lewis, J. Phys. Chem. C 114, 28 (2010)