Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 2: Hauptvortrag Nilius

O 2.1: Hauptvortrag

Montag, 8. März 2004, 10:15–11:00, H36

Tailoring electronic properties of atomic chains assembled in the STM — •Niklas Nilius1, Thomas M. Wallis2, and Wilson Ho21Fritz-Haber-Institut der MPG, Berlin — 2University of California, Irvine, USA

The physical and chemical properties of ultra-small metal aggregates sensitively depend on number and precise position of atoms in the structure. Various applications in heterogeneous catalysis, optics and electronics take advantage of this size-dependent behavior. However, preparation and analysis of well-defined metal aggregates on surfaces are demanding and interrelations between structural and electronic properties are not well understood on the atomic level. In the present work, atom manipulation techniques with an STM tip have been employed to construct precise metal structures on a NiAl(110) surface. Single Au and Pd atoms were assembled to atomic chains, whereby discrete adatom-resonances develop into a series of quantum well states showing a parabolic dispersion. Modifications of structural chain parameters, such as inter-atomic distance, elemental composition and local impurities, decisively influence the electronic properties of the atomic chains. Adsorption of a single CO molecule on a Au chain interrupts the coupling between neighboring chain atoms, breaking the chain into two independent electron systems. A similar effect is observed upon introducing a single Pd atom into Au chains. On the other side, the regular alternation of Pd and Au atoms in alloy chains leads to properties in between those of pure Au and Pd chains. The experiments demonstrate the possibility to manufacture and characterize quantum systems with a well-defined electronic structure.

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