Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 62: Metal Substrates: Adsorption of Inorganic Molecules
O 62.1: Talk
Thursday, February 28, 2008, 09:30–09:45, MA 042
Tuning Surface Energy Landscapes in Metallic Quantum Films using Alkali Adsorbates — •Alexander Khajetoorians1, Shengyong Qin1, Wenguang Zhu2, Holger Eisele1, Zhenyu Zhang2, and Chih-Kang Shih1 — 1Department of Physics, University of Texas at Austin, Austin, Texas, USA — 2Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
Quantum confinement shows a strong interplay with growth and kinetics in thin metal systems where the Fermi wavelength has a special relationship to the surface normal lattice constant. In the case of Pb/Si(111) systems, this relationship reveals an interesting thickness-dependent bilayer oscillation in the density of states up to a phase. In the limit where surface energy oscillations are strong, this interplay can result in the formation of magic quantum stable islands and film thicknesses. In this paper, we report on a novel effect: tuning of the energy landscape of a flat-top quantum Pb mesa using Cs adsorbates. Using STM/STS, we show that depositing Cs adsorbates on a thin Pb mesa promotes quantum stable Pb nanoislands on preferentially unstable thicknesses. Thickness-dependent nanoisland densities show a strong bilayer oscillation correlating with quantum stability. By modifying the Cs coverage on the mesa surface, we can tune the lateral size distribution of the nanoislands and the overall amplitude of the island density oscillation. Nanoisland formation seems intricately linked to a step decoration of Cs adatoms along the step edge of the nanoisland. The role of surface reactivity on these properties will also be discussed. Support: NSF-IGERT DGE-0549417; NSF-FRG 26-1126-8750