Poster
Surface Dynamics of the Wetting Layer and of 2 to 4 Lead Monolayers on Cu(111)
1Tomsk State University, pr. Lenina 36, 634050, Tomsk, Russian Federation, and Institute of Strength Physics and Materials Science, pr. Academicheskii 2/4, 634021, Tomsk, Russian Federation
2Donostia International Physics Center (DIPC); Department of Materials Physics, University of the Basque Country (UPV/EHU), 20018 San Sebastian/Donostia, Spain
3Centro de Física de Materiales CFM, Centro Mixto CSIC-UPV/EHU, 20018 San Sebastian /Donostia, Spain
4Dipartimento di Scienza dei Materiali, Universitá di Milano-Bicocca, Via Cozzi 55, 20125 Milano, Italy
5Max-Planck-Institut für Dynamik und Selbstorganisation, Bunsenstraße 10, 37073 Göttingen, Germany
The growth of Pb ultra-thin films on Cu(111) has been long studied in connection with electronic band-structure quantum-size effects and for the transition from the low-temperature layer-by-layer Frank-van-der-Merwe to the high-temperature Stranski-Kastanov growth regime at room T. At low temperature the formation of a wetting layer (1 monolayer (ML)), an instability of the 2 ML film and a regular layer-by-layer growth for more than 2 ML are observed; the 2 ML film was shown to be stabilized by alloying Pb with 20% Tl [3]. In this work we present a theoretical study of the dynamics of the wetting layer as well as for 2 ML Pb0.8Tl0.2, 3 ML and 4 ML Pb on Cu(111) in the 4×4 commensurate phase, for which detailed inelastic Helium atom scattering (HAS) spectra have been measured. The present calculations is based on the embedded atom (EA) method. Besides leading to a detailed interpretation of the HAS experimental data, the present results integrate a previous density-functional perturbation theory (DFPT) study for 3 to 7 ML Pb on a rigid substrate [1,2] with an analysis of the role plaid by the substrate dynamics at the smallest thicknesses, which is quite relevant despite the large mass and stiffness differences between Pb and Cu. Also the different thermal expansion of the film with respect to the substrate is shown to cause appreciable anomalies in the temperature and thickness dependence of the phonon dispersion curves.
Research partially was supported by grant (No. 8.1.05.2015) from "The Tomsk State University Academic D. I. Mendeleev Fund Program" and by grant RFBR (No. 15-02-02717-a).
[1] I. Yu. Sklyadneva, G. Benedek, E. V. Chulkov, P. M. Echenique, R. Heid, K.-P. Bohnen and J. P. Toennies, Phys. Rev. Lett. 107, 095502 (2011)
[2] G. Benedek, M. Bernasconi, K.-P. Bohnen, D. Campi, E. V. Chulkov, P. M. Echenique, R. Heid, I. Yu. Sklyadneva and J. P. Toennies, Phys. Chem. Chem. Phys. 16, 7159 (2014)
[3] J. Braun, J. P. Toennies, Surf. Sci. 368, 226 (1996)