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    Oxygen-deficient oxide growth by subliming the oxide source material: The cause of silicide formation in rare earth oxides on silicon
    (Washington, DC : ACS, 2013) Bierwagen, O.; Proessdorf, A.; Niehle, M.; Grosse, F.; Trampert, A.; Klingsporn, M.
    The fundamental issue of oxygen stoichiometry in oxide thin film growth by subliming the source oxide is investigated by varying the additionally supplied oxygen during molecular beam epitaxy of RE2O3 (RE = Gd, La, Lu) thin films on Si(111). Supplying additional oxygen throughout the entire growth was found to prevent the formation of rare earth silicides observed in films grown without an oxygen source. Postgrowth vacuum annealing of oxygen stoichiometric films did not lead to silicide formation thereby confirming that the silicides do not form as a result of an interface instability at growth temperature in vacuum but rather due to an oxygen deficiency in the source vapor. The average oxygen deficiency of the rare-earth containing species in the source vapor was quantified by the 18O tracer technique and correlated with that of the source material, which gradually decomposed during sublimation. Therefore, any oxide growth by sublimation of the oxide source material requires additional oxygen to realize oxygen stoichiometric films.
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    A novel engineered oxide buffer approach for fully lattice-matched SOI heterostructures
    (College Park, MD : Institute of Physics Publishing, 2010) Giussani, A.; Zaumseil, P.; Seifarth, O.; Storck, P.; Schroeder, T.
    Epitaxial (epi) oxides on silicon can be used to integrate novel device concepts on the canonical Si platform, including functional oxides, e.g. multiferroics, as well as alternative semiconductor approaches. For all these applications, the quality of the oxide heterostructure is a key figure of merit. In this paper, it is shown that, by co-evaporating Y2O3 and Pr2O3 powder materials, perfectly lattice-matched PrYO3(111) epilayers with bixbyite structure can be grown on Si(111) substrates. A high-resolution x-ray diffraction analysis demonstrates that the mixed oxide epi-films are single crystalline and type B oriented. Si epitaxial overgrowth of the PrYO3(111)/Si(111) support system results in flat, continuous and fully lattice-matched epi-Si(111)/PrYO3(111)/Si(111) silicon-on-insulator heterostructures. Raman spectroscopy proves the strain-free nature of the epi-Si films. A Williamson-Hall analysis of the mixed oxide layer highlights the existence of structural defects in the buffer, which can be explained by the thermal expansion coefficients of Si and PrYO3. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.