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Stability Study of Highly Dispersed Au Clusters Produced on Defected TiO2 (110); Evidence from SEM and Olefin TPD

Published online by Cambridge University Press:  01 February 2011

Y. Yang  and
E. McFarland
Y. Yang
Affiliation:
Dept. Chemical Engineering, University of California, Santa Barbara, CA 93117, U.S.A.
E. McFarland
Affiliation:
Dept. Chemical Engineering, University of California, Santa Barbara, CA 93117, U.S.A.
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Abstract

The stability of Au nanoclusters created at defect sites on TiO2(110) surfaces is under investigation. Using Ar ion sputtering, 0 - 10% of the surface area of ideal surfaces are modified with defects at a controlled defect density. Defected surfaces are also produced using controlled vacuum heating to 1300 K for 25 minutes. Identical exposures (< 1Å) of Au were evaporated on each surface and results of propylene temperature programmed desorption (TPD) heating cycles to < 700 K are compared with ideal control surfaces. Results support the model that Au deposited on a sputtered surface is immobilized at defect sites and the clusters so formed are stable with respect to sintering. As previously observed, with increased sputtering time there is a decrease in the cluster size and increased defect density. The desorption peak of propylene from the Au-TiO2 surface is used as an in situ probe of cluster size stability. By cyclically performing TPD to 700 K for longer times and additional cycles (or higher temperature), the sintering stability can be assessed. On the sputtered TiO2 (110) surface, evaporated gold clusters sinter with only ∼25% maintaining their initial size. On the unsputtered 1300 K annealed TiO2, Au is stable with respect to sintering for many cycles of 800 K heating. This phenomenon is attributed to both the surface stability and Au affinity for the thermal defects created on the surface. This work extends our previous investigations of Au cluster formation on defected TiO2 to their stability with respect to sintering.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 854: Symposium U – Stability of Thin Films and Nanostructures , 2004 , U5.2
Copyright
Copyright © Materials Research Society 2005

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