Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 17: Oxides and insulators III

O 17.6: Vortrag

Dienstag, 24. März 2009, 11:45–12:00, SCH A01

Tailoring the adsorption properties of SiO2 thin films — •Jan-Frederik Jerratsch, Niklas Nilius, and Hans-Joachim Freund — Fritz-Haber-Institut der MPG, D14195 Berlin, Germany

An ultra-thin silica film grown on Mo(112) can be chemically modified by inserting Li atoms into the nano-pores of the oxide material. The Li becomes cationic upon incorporation and considerably reduces the silica/Mo work function by creating a positive surface dipole. The smaller work function facilitates charge transfer processes from the Mo support into adsorbates on the surface. The hence negatively charged ad-species have a much larger binding energy due to Coulomb interactions with the support. This principle is demonstrated for gold deposited onto Li/silica/Mo(112) using a low temperature STM. Whereas single Au atoms and small clusters are anchored on the Li-modified surface, they are unable to bind to the pristine oxide film.