Spectro-microscopic characterization of thin Fe-oxide films: interconversion and effects of metal (Fe-Pt) deposition

Iron oxide, widely used as a catalyst and as a support for catalytically active systems, has been intensively studied with various techniques. However, still, the link between surface termination, surface electronic and structural properties to chemical properties is controversial. Moreover, such properties can be modified and controlled by preparation [1] and/or metal deposition [2].

Taking advantage of real time observation of real and diffraction space (LEEM and LEED) and chemical information in XPEEM, we have investigated (a) the phase transformation Fe₃O₄ →Fe₂O₃ under different oxidation conditions[3]; (b) the surface modifications of Fe₃O₄ and Fe₂O₃ thin films by Fe deposition, and (c) their interaction with Pt nanoparticles (SMSI) [2, 4] . The experiment were carried out at the SMART instrument [5], operating at BESSY-2, the soft x-ray light source of the Helmholtz Center in Berlin.

1. Defects and inhomogeneities in Fe₃O₄ (111) thin film growth on Pt (111).
   Sala, A., et al., Physical Review B, 2012. 86(15): p. 155430.
2. Promotional effect of metal encapsulation on reactivity of iron oxide supported Pt catalysts.
   Lewandowski, M., et al., Applied Catalysis A: General, 2011. 391(1): p. 407-410.
3. Interconversion of α-Fe₂O₃ and Fe₃O₄ thin films: mechanisms, morphology, and evidence for unexpected substrate participation.
   Genuzio, F., et al., The Journal of Physical Chemistry C, 2014.
4. Scanning Tunneling Microscopy study of iron oxide based model catalysts, in prozesswissenshaften.
   Lewandowsky, M., 2011, Technische Universität: Berlin.
5. An aberration-corrected XPEEM/LEEM with energy filter.
   Wichtendahl, R., et al., SMART: Surface Review and Letters, 1998. 5(06): p. 1249-1256.

Chemical Physics department, Fritz Haber Institut der Max Plank