Epitaxial oxide thin film layers are of interest for model catalytic studies. We report the growth of Ce1 - xPrxO2 - delta mixed oxide layers of different stoichiometries (x = 0-1) and oxygen deficiency (delta >0) on Si(111) by co-evaporating molecular beam epitaxy. The main objective is to identify the crystal phases and to investigate the correlation between compositions and crystal structures. X-ray photoemission spectroscopy was performed to quantify the stoichiometries. An extensive laboratory and synchrotron based X-ray diffraction analysis was carried out to determine the vertical and lateral lattice orientations and the strain status of the layers. The study revealed that single crystalline Ce1 - xPrxO2 - delta/Si(111) heterostructures can be epitaxially grown on Si(111) for model catalytic studies. In addition to the structure-stoichiometry relationship typical to mixed oxide bulk powders, we identified a hexagonal mixed Ce-Pr oxide thin film phase not yet reported in bulk studies. (C) 2012 Elsevier B.V. All rights reserved.