Von Pr2O3 zu PrO2 - Interdisziplinäre Studie zum Einfluss von Volumen- und Oberflächendefekten auf Materialeigenschaften geordneter Praseodymoxid-Schichten

• Applicants: Professor Dr. Marcus Bäumer; Professor Dr. Michael Reichling; Professor Dr. Thomas Schröder; Professor Dr. Joachim Wollschläger
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2009 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 142317448

• Final Report Year: 2016

Final Report Abstract

Rare earth praseodymium and cerium oxides have attracted intense research interest in the last decades, due to their intriguing chemical and physical characteristics. An understanding of the correlation between structure and properties, in particular the surface chemistry, has been the major goal of this project to develop praseodymia and ceria systems for future applications in microelectronics, catalysis, optics and other fields. Such an understanding has, so far, been hampered by the complexity of rare earth oxide materials and experimental methods for their characterisation. We studied high-quality, single crystalline, praseodymium and cerium oxide films as well as ternary alloys grown on Si (111) substrates. Using these well-defined systems and based on a systematic multi-technique surface science approach, the corresponding physical and chemical properties, such as the surface structure, the surface morphology, the bulk-surface interaction and the oxygen storage/release capability have been explored in great detail. We demonstrated that specifically the crystalline structure and the oxygen stoichiometry of the oxide thin films can be well controlled by the film preparation method. This work lead to a comprehensive understanding of properties of rare earth oxides and highlights applications of these versatile materials. Furthermore, methanol adsorption studies have been performed on binary and ternary rare earth oxide thin films, demonstrating the feasibility of employing such systems for model catalytic studies. Specifically for ceria systems, we found considerable stability against normal environmental conditions so that they can be considered as a “materials bridge” between surface science models and real catalysts.

Publications

• Morphology and nanostructure of CeO2(111) surfaces of single crystals and Si(111) supported ceria films, Physical Chemistry Chemical Physics 14, 15361 (2012)
  H. H. Pieper, C. Derks, M. H. Zoellner, R. Olbrich, L. Tröger, T. Schroeder, M. Neumann, M. Reichling
  
• Stacking behavior of twin-free type-B oriented CeO2(111) films on hexagonal Pr2O3(0001)/Si(111) systems, Physical Review B 85, 035302 (2012)
  M. H. Zoellner, J. Dabrowski, P. Zaumseil, A. Giussani, M. A. Schubert, G. Lupina, H. Wilkens, J. Wollschläger, M. Reichling, M. Bäumer, T. Schroeder
  
• Stoichiometry-Structure Correlation of Epitaxial Ce1-xPrxO2-d (x=0-1) Thin Films on Si(111), J. Cryst. Growth 355, 159 (2012)
  M. H. Zoellner, P. Zaumseil, H. Wilkens, S. Gevers, J. Wollschläger, M. Bäumer, Y.-H. Xie, G. Niu, T. Schroeder
  
• Lattice-matched Epitaxial Ternary PrxY2-xO3 Films on SrO-Passivated Si (001): Interface Engineering and Crystallography Tailoring, Appl. Phys. Lett. 102, 011906 (2013)
  G. Niu, P. Zaumseil, M. A. Schubert, M. H. Zoellner, J. Dabrowski, T. Schroeder
  
• Stabilization of the ceria iota-phase (Ce7O12) surface on Si(111), Applied Physics Letters 102, 111602 (2013)
  H. Wilkens, O. Schuckmann, R. Oelke, S. Gevers, A. Schaefer, M. Bäumer, M. H. Zoellner, T. Schroeder, J. Wollschläger
  
• Structural transitions of epitaxial ceria films on Si(111), Physical Chemistry Chemical Physics 15, 18589 (2013)
  H. Wilkens, O. Schuckmann, R. Oelke, S. Gevers, M. Reichling, A. Schaefer, M. Bäumer, M. H. Zoellner, G. Niu, T. Schroeder, J. Wollschläger
  
• A well-structured metastable ceria surface, Applied Physics Letters 104, 081910 (2014)
  R. Olbrich, H. H. Pieper, R. Oelke, H. Wilkens, J. Wollschläger, M. H. Zoellner, T. Schroeder, M. Reichling
  
• Structural Changes of Ultrathin Cub-PrO2 (111)/Si (111) Films Due to Thermally Induced Oxygen Desorption, J. Phys. Chem. C 118, 3056 (2014)
  H. Wilkens, S. Gevers, S. Röhe, A. Schaefer, M. Bäumer, M. H. Zoellner, T. Schroeder, J. Wollschläger
  
• Controlling the physics and chemistry of binary and ternary praseodymium and cerium oxide systems, Physical Chemistry Chemical Physics 17, 24513 (2015)
  G. Niu, M. H. Zoellner, T. Schroeder, A. Schaefer, J. H. Jhang, V. Zielasek, M. Bäumer, H. Wilkens, J. Wollschläger, R. Olbrich, C. Lammers, M. Reichling
  
• Postdeposition annealing of epitaxial Ce1-xPrxO2 films grown on Si(111), Physical Chemistry Chemical Physics 17, 9991 (2015)
  H. Wilkens, W. Spieß, M.H. Zoellner, G. Niu, T. Schroeder, and J. Wollschläger