Berlin 2005 – wissenschaftliches Programm
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DF: Dielektrische Festkörper
DF 4: Poster
DF 4.14: Poster
Samstag, 5. März 2005, 08:30–16:30, Poster TU C
Phase formation sequence during thin film solid-state reactions in the BaO-TiO2 system — •Andriy Lotnyk, Andreas Graff, Stephan Senz, and Dietrich Hesse — Max-Planck-Institut für Mikrostrukturphysik, D-06120 Halle, Germany
A BaCO3 target is e-beam evaporated in a high vacuum system with an oxygen background pressure of 1×10−2 Pa. The single crystal TiO2 rutile substrate is heated between 300∘C and 900∘C. Reaction products are investigated by XRD and analytical TEM (EELS). A deposition at 500∘C followed by solid-solid reaction at 600∘C for 30 min produced the metastable intermediate Ba2TiO4 phase without any evidence of BaTiO3 formation. It may be explained by Ti diffusion into the BaO thin film. The epitaxial relationship of the Ba2TiO4 (B2T) to the (110) rutile surface (T) is (110)B2T∥(110)T and [001]B2T∥[001]T. The Ba2TiO4 phase is completely decomposed after two weeks of storage in air by reaction with H2O and CO2. A gas-solid and solid-solid reaction at 700∘C and 800∘C leads to the formation of BaTiO3 and Ba2TiO4. The orientation relationship of the Ba2TiO4 changes compared to the 600∘C solid-solid reaction.
A gas-solid reaction at 900∘C resulted in large pores between the substrate and the thin film. The film was converted almost completely to a Ti-rich phase covered by the remaining BaTiO3. The Ti-rich phase was identified by pole figure analyses as Ba4Ti12O27.