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    Heteroepitaxial growth of T-Nb2O5 on SrTiO3
    (Basel : MDPI, 2018) Boschker, Jos E.; Markurt, Toni; Albrecht, Martin; Schwarzkopf, Jutta
    There is a growing interest in exploiting the functional properties of niobium oxides in general and of the T-Nb2O5 polymorph in particular. Fundamental investigations of the properties of niobium oxides are, however, hindered by the availability of materials with sufficient structural perfection. It is expected that high-quality T-Nb2O5 can be made using heteroepitaxial growth. Here, we investigated the epitaxial growth of T-Nb2O5 on a prototype perovskite oxide, SrTiO3. Even though there exists a reasonable lattice mismatch in one crystallographic direction, these materials have a significant difference in crystal structure: SrTiO3 is cubic, whereas T-Nb2O5 is orthorhombic. It is found that this difference in symmetry results in the formation of domains that have the T-Nb2O5 c-axis aligned with the SrTiO3 <001>s in-plane directions. Hence, the number of domain orientations is four and two for the growth on (100)s- and (110)s-oriented substrates, respectively. Interestingly, the out-of-plane growth direction remains the same for both substrate orientations, suggesting a weak interfacial coupling between the two materials. Despite challenges associated with the heteroepitaxial growth of T-Nb2O5, the T-Nb2O5 films presented in this paper are a significant improvement in terms of structural quality compared to their polycrystalline counterparts.
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    XPS investigations of MOCVD tin oxide thin layers on Si nanowires array
    (Amsterdam : Elsevier, 2018) Turishchev, S.Yu.; Chuvenkova, Olga; Parinova, V.E.; Koyuda, D.A.; Chumakov, Ratibor G.; Presselt, Martin; Schleusener, Alexander; Sivakov, Vladimir
    Tin oxide thin layers were grown by metal-organic chemical vapor deposition technique on the top-down nanostructured silicon nanowires array obtained by metal-assisted wet-chemical technique from single crystalline silicon wafers. The composition of the formed layers were studied by high-resolution X-ray photoelectron spectroscopy of tin (Sn 3d) and oxygen (O 1 s) atoms core levels. The ion beam etching was applied to study the layers depth composition profiles. The composition studies of grown tin oxide layers is shown that the surface of layers contains tin dioxide, but the deeper part contains intermediate tin dioxide and metallic tin phases.