The origin of the superstructure observed in epitaxial Y2O3 layers on Si (001) was determined by electron energy loss spectroscopy. The oxygen K edge was measured both in the superstructure and a defect-free region of the Y2O3 layers and they were compared to electron energy loss spectra obtained from bulk stoichiometric and reduced Y2O3. It was shown that as a result of the epitaxial growth, O vacancies order into a superstructure creating non-stoichiometric regions in an otherwise stoichiometric Y2O3 layer. Furthermore, it was shown that O deficiency introduces a change of the density of states of the lower conduction band of Y2O3.

Oxygen Vacancy Ordering in Epitaxial Layers of Yttrium Oxide on Si (001). A.Travlos, N.Boukos, G.Apostolopoulos, A.Dimoulas: Applied Physics Letters, 2003, 82[23], 4053-5