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 Karl Franzens University Graz

Graz University of Technology 

Metal Oxide Surfaces Viewed at the Atomic Scale
Univ.Prof. Dipl.-Ing. Dr. Ulrike DIEBOLD
Institut für Angewandte Physik, Technische Universität Wien
17:00 - 18:00 Tuesday 29 November 2011 KFU

During the past decades scanning tunneling microscopy (STM) has evolved as a powerful tool to obtain immediate and direct insights into processes and phenomena at surfaces. In lockstep with the refinement of experimental techniques density functional theory (DFT) has been pushed to a level where large enough systems can be modeled with sufficient accuracy to become very useful in surface physics. The marriage of theory and experiment has been very
fertile: with STM one is able to image complex structures and follow the fate of single atoms or molecules, and modeling with DFT is invaluable for interpreting atomically-resolved STM images.

The talk will be mainly concerned with the surfaces of oxides [1] for two simple reasons: first, most metals are oxidized in the ambient atmosphere, so these are the types of surfaces that we mostly encounter in nature. Second, oxides are materials with an extremely wide range of physical properties, hence are used in many technical fields. In virtually all applications surfaces and interfaces play a decisive role, so a more complete fundamental understanding of the low-dimensional properties of metal oxides can impact a variety of research areas.

I will give a few example of recent results of STM studies of metal oxide materials, often combined with insights from DFT. I will discuss the diffusion mechanism of a small organic molecule across a TiO2(110) surface [2], the adsorption and dissociation of O2 [3], why adsorbed water molecules can apparently repel each other when adsorbed to a surface [4], and how oxygen vacancies, produced by electron bombardment [5] move from the surface to the subsurface region [6].

1. U. Diebold, S.-C. Li, and M. Schmid "Oxide Surface Science", Ann. Rev. Phys. Chem., 61 (2010) 131 2. S.-C. Li, et al. "Hydrogen controls the dynamics of catechol adsorbed on a TiO2(110) surface" Science 328 (2010) 882 3. Ph. Scheiber et al. "Observation and Destruction of an Elusive Adsorbate with STM: O2/TiO2(110)" Phys. Rev. Lett., 105 (2010) 216101 4. O. Dulub, et al. "Formation of defects on TiO2 under electron bombardment: site-specific oxygen desorption" Science 317 (2007) 1052 5. Y. He, et al. "Local ordering and electronic signatures of submonolayer water on anatase TiO2(101)"Nat. Mater. 8 (2009) 585 6. Y. He, et al. "Evidence for the Predominance of Subsurface Defects on TiO2 Anatase (101)" Phys. Rev. Lett., 102 (10) (2009) 106105.