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 Karl Franzens University Graz

Graz University of Technology 

Designing epitaxial rare-earth oxide films and nanostructures for heterogeneous model catalysis
Dr. Jan Ingo Flege
Institute of Solid State Physics, University of Bremen,Germany
17:00 - 18:00 Tuesday 29 November 2016 KFU

Ultrathin rare-earth oxide films and nanostructures are of considerable interest due to their exceptional physical and chemical properties, which make them attractive for a wide range of technological applications including, e.g., microelectronics, energy harvesting and storage, sensing, and heterogeneous catalysis. Their special materials characteristics directly originate from their detailed structural properties in combination with the peculiar electronic configurations of the rare earth metal cations, namely their partially filled 4f electron shells. Taking into account the frequently observed heterogeneous sample morphology, a detailed understanding of the fundamental processes and mechanisms that determine the oxide functionality hence requires an in-depth multiscale analysis from the micrometer down to the atomic length scale.

In this presentation, I will focus on the growth and characterization of rare-earth metal oxide films deposited on transition metals and subsequent monitoring of their structural and chemical modifications in reactive environments using low-energy electron microscopy and related methods. This in situ diffractive imaging technique has proven successful in unraveling, on the same footing, the atomic-scale structure, the mesoscale morphology, and the reactivity of the combined metal/oxide system [1], e.g., of the frequently employed ceria(111)/Ru(0001) inverse model catalyst [2], demonstrating ordered and heterogeneous structural transformations upon chemical reduction [3]. Recently, we have also been able to selectively synthesize ceria(100) nanostructures and microparticles on close-packed transition metal surfaces, with different mechanisms responsible for their growth [4,5]. These findings will be compared with in situ growth studies of the related systems praseodymia on Ru(0001) [6] and terbia on Cu(111) [7], demonstrating the intricate interplay of various thermodynamic and kinetic factors that give rise to this structural richness. Taken together, these results pave the road for a new understanding of oxide growth on metal supports and open up the exciting possibility of designing model catalyst architectures of desired surface morphology and composition for comparative reactivity and selectivity studies under identical conditions.


[1] J. I. Flege and E. E. Krasovskii, Phys. Status Solidi RRL 8, 463 (2014).
[2] D. C. Grinter et al., Appl. Catal. B: Environmental 197, 286 (2016).
[3] J. Höcker et al., Adv. Mater. Interfaces 2, 1500314 (2015).
[4] J. Höcker et al., J. Phys. Chem. C 120, 4895 (2016).
[5] J. I. Flege et al., Nanoscale 8, 10849 (2016).
[6] J. Höcker et al., Phys. Chem. Chem. Phys., accepted.
[7] J. Höcker et al., J. Phys. Chem. C 119, 14175 (2015).