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O: Fachverband Oberflächenphysik

O 81: Oxides and Insulator Surfaces I

O 81.8: Vortrag

Donnerstag, 10. März 2016, 12:30–12:45, H4

In-situ electron microscopy studies of praseodymia on Ru(0001) — •Jon-Olaf Krisponeit¹, Jan Höcker¹, Andreas Schäfer², Julian Cambeis¹, Alexei Zakharov², Yuran Niu², Jens Falta¹, and Jan Ingo Flege¹ — ¹University of Bremen, Bremen, Germany — ²Lund University, Lund, Sweden

Due to the multiple valence states of rare earth elements, their oxides (REOs) play an important role in catalysis applications. A prominent example is ceria, which is well known for its oxygen storage capacity. Grown as microparticles on Ru(0001), ceria shows an excellent crystalline quality and thermal stability, making it well suited for catalytic model studies. We extend these efforts to the less studied praseodymia, which exhibits an intriguingly complex phase diagram with many stable mixed-valence compounds between Pr₂O₃ and the fully-oxidized PrO₂. Furthermore, praseodymia shows the highest oxygen mobility among the REOs, rendering PrO_x/Ru(0001) an attractive inverse catalyst model system.

We have prepared ultra-thin films of PrO_x/Ru(0001) by reactive molecular beam epitaxy. Here, we present in-situ investigations on local morphology and structure by low energy electron microscopy and micro-illumination diffraction (LEEM/µ-LEED), revealing the nucleation of triangular islands and the formation of rotational domains. Furthermore, we studied the local chemical composition by x-ray absorption spectroscopy in imaging mode (XAS-PEEM) and discuss post-oxidation and reduction processes as identified by x-ray photoelectron spectroscopy (XPS).