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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.