Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 28: Symposium: Size-Selected Clusters at Surfaces II
(Invited Speakers: Steven Buratto, Stefan Vajda, Matthias Arenz)

O 28.1: Hauptvortrag (ohne Erstattung)

Dienstag, 26. Februar 2008, 11:15–11:45, MA 005

Size-selected Au and Ag nanoclusters on rutile TiO2 (110) (1x1) surfaces probed by UHV-STM — Xiao Tong, Lauren Benz, Steeve Chretien, Paul Kemper, Michael Bowers, Horia Metiu, and •Steven Buratto — University of California, Santa Barbara, CA USA

Catalysis of the oxidation of CO and small olefins by Au and Ag nanoclusters on oxide supports is known to be strongly dependent on the size of the cluster and its interaction with the oxide surface. In our group we have probed this size dependence by depositing size-selected clusters of Agn+ and Aun+ (n = 1-7) from the gas phase onto single crystal rutile TiO2 (110) (1x1) surfaces at room temperature under soft-landing (< 2 eV/atom) conditions. We analyze the clusters on the surface using ultra-high vacuum scanning tunneling microscopy (UHV-STM) and compare the resulting structures with theory. In the case of Aun+ , Ag+ and Ag2+ clusters deposited under soft-landing conditions we observe large, sintered clusters indicating high mobility for these species on the surface. For Aun+ (n > 1) and Agn+ (n > 2) clusters deposited under soft-landing conditions, however, we observe a high density of intact clusters bound to the surface indicating that these species have very limited mobility on the surface. We have also shown that the sintering of Au+ soft-landed on TiO2 (110) occurs only for a surface covered with hydroxyl groups. On a pristine surface with an oxygen vacancy density near 10%, Au atoms remain intact on the surface.