Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 14: Adsorption on semiconductors, oxides and insulators II

O 14.1: Vortrag

Montag, 26. März 2012, 16:00–16:15, MA 041

Gold adsorption on pristine and defective ceria films — •Yi Pan, Niklas Nilius, and Hans-Joachim Freund — Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany

Scanning tunnelling microscopy and spectroscopy have been employed to study the adsorption of individual Au adatoms on well defined CeO2(111) films grown on Ru(0001). In correspondence with recent DFT calculations, the Au adatoms can be stabilized in two charge states on the oxide surface, giving rise to the appearance of features with different size and bias-dependent contrast in the STM. The relative abundance of the two species sensitively depends on the reduction state of the surface, i.e. on the density of oxygen vacancies. This interrelation suggests that an exchange of electrons between the adatoms and the Ce 4f states is responsible for the bi-modal charge distribution. Moreover, the Au charge state can be switched reversibly via electron injection from the STM tip, providing insight into the nature of the participating Au electronic states.