Growth and structural dynamics of nanoscale epitaxial oxides for catalysis: an in situ perspective

by Jan-Ingo Flege (Inst. of Solid State Physics, Univ. Bremen)

Wednesday, June 14, 2017 from to (Europe/Berlin)
at DESY Hamburg ( Bldg. 01b/Sem.R. 4a )
Description Oxides are ubiquitous in our modern world and play a prominent role in a variety of every-day phenomena, e.g., as rather unwanted products of corrosion or as a crucial component in heterogeneous catalysis and microelectronics. Generally, oxide functionality is determined by the oxide’s atomic structure and morphology, which are deeply intertwined with its synthesis and which result in specific chemical and electronic properties. Especially the technologically relevant transition metal and rare-earth oxides exhibit a variety of crystal structures and oxidation states, rendering the analysis of the structure-function relationship rather complex and experimentally very challenging to address. Furthermore, their materials properties are heavily influenced by the structure and composition of the oxide surface mediating the interaction of the oxide/metal system with its surrounding.
In my presentation, I will demonstrate what kind of novel insights into growth processes of ultrathin oxide films and nanostructures as well as surface chemical redox reactions can be gained by applying low-energy electron microscopy (LEEM) and related techniques. Besides offering a lateral resolution down to ten nanometers or below at video rates, even time-resolved probing of changes in local atomic and electronic structure is possible [1]. This experimental approach is particularly attractive in nanoheterogeneous systems exposed to reactive environments since not only the various surface components may be investigated individually, but also potential cooperative effects mediated by their coexistence and close proximity. Selected examples will include the oxidation of the Ru(0001) single crystal surface [2-3] as well as the epitaxial growth and chemistry of transition metal supported rare-earth oxide nanostructures [4-8].

[1] J. I. Flege and E. E. Krasovskii, Phys. Status Solidi RRL 8, 463 (2014). [2] J. I. Flege, B. Herd, J. Goritzka, H. Over, E. E. Krasovskii, and J. Falta, ACS Nano 9, 8468 (2015). [3] J. I. Flege, J. Lachnitt, D. Mazur, P. Sutter, and J. Falta, Phys. Chem. Chem. Phys. 18, 213 (2016). [4] D. C. Grinter, S. D. Senanayake, and J. I. Flege, Appl. Catal. B: Environmental 197, 286 (2016). [5] J. Höcker, T. O. Menteş, A. Sala, A. Locatelli, Th. Schmidt, J. Falta, S. D. Senanayake, and J. I. Flege, Adv. Mater. Interfaces 2, 1500314 (2015). [6] J. I. Flege, J. Höcker, B. Kaemena, T. O. Menteş, A. Sala, A. Locatelli, S. Gangopadhyay, J. T. Sadowski, S. D. Senanayake, and J. Falta, Nanoscale 8, 10849 (2016). [7] J. Höcker, J.-O. Krisponeit, Th. Schmidt, J. Falta, and J. I. Flege, Nanoscale, in press (2017). DOI: 10.1039/c6nr09760j [8] J. I. Flege, J.-O. Krisponeit, J. Höcker, M. Hoppe, Y. Niu, A. Zakharov, A. Schaefer, J. Falta, and E. E. Krasovskii, Ultramicroscopy, in press (2017). DOI: 10.1016/j.ultramic.2017.05.007