Morphological and chemical characterization of thin heteroepitaxial praseodymium sesquioxide films on Si(111)

Among the rare earths praseodymium oxides possess the highest oxygen mobility and a high oxygen storage capability. Due to this fact they are promising candidates for catalytic applications exploiting the variable valency of Pr. A simplified two dimensional model system of the oxide catalyst can be prepared on silicon substrates in an UHV environment to study the atomic details of oxygen transport and transfer when exposed to adsorbed molecules. Here we report on the growth and morphology of heteroepitaxial Pr2O3 films at a low deposition rate on Si(111) which were investigated using spot profile analysis of low-energy electron diffraction. In the initial stages of growth the specular diffraction spot exhibits a pronounced threefold symmetry most likely reflecting the formation of highly ordered islands of triangular shape as shown by STM. A roughening of the substrate surface is observed during growth of the initial Praseodymium oxide layer. Beyond these morphological studies, preliminary results of a first chemical characterization of the films with and without adsorbates (CO and oxygen) by XAS and XPS will be presented