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O: Fachverband Oberflächenphysik
O 26: Nanostructures at surfaces: Dots, particles, clusters II (SPM)
O 26.1: Vortrag
Dienstag, 24. März 2009, 15:00–15:15, SCH A215
Quantum well states in two-dimensional gold clusters — Xiao Lin1, •Niklas Nilius1, Hans-Joachim Freund1, Michael Walter2, Pentti Frondelius2, Karolina Honkala2, and Hannu Häkkinen2 — 1Fritz-Haber Institut der MPG, D14195 Berlin, Germany — 2Department of Physics, University of Jyväskylä, FI-40014 Finland
The electronic structure of ultra-small Au clusters on thin MgO/Ag(001) films is analyzed by scanning tunneling spectroscopy and density functional theory. The clusters exhibit two-dimensional quantum well states, whose shapes resemble the eigenstates of a 2D electron gas confined in a parabolic potential. From the HOMO and LUMO symmetries, the electron filling and charge state of particular clusters are determined. In accordance to a DFT charge-analysis, the aggregates accumulate a number of excess electrons due to charge transfer from the support. Monitoring the HOMO-LUMO gap as a function of cluster size, the transition from non-metallic to metallic Au behavior is deduced for clusters containing 70-100 atoms.