D. Hesse, N. D. Zakharov, A. Pignolet, A. R. James, S. Senz: TEM Cross-Section Investigations of Epitaxial Ba2Bi4Ti5O18 Thin Films on LaNiO3 Bottom Electrodes on CeO2/YSZ-Buffered Si(100)

Crystal Research and Technology

Cryst. Res. Technol. 35 (2000) 641 - Abstract -

D. Hesse, N. D. Zakharov, A. Pignolet, A. R. James, S. Senz

Max-Planck-Institut für Mikrostrukturphysik, Halle, Germany

TEM Cross-Section Investigations of Epitaxial Ba₂Bi₄Ti₅O₁₈ Thin Films on LaNiO₃ Bottom Electrodes on CeO₂/YSZ-Buffered Si(100)

Epitaxial, ferroelectric Ba₂Bi₄Ti₅O₁₈ films grown on LaNiO₃/CeO₂/ZrO₂:Y₂O₃ epi-taxial layers on Si(100) are investigated by plan-view and cross-section transmission electron microscopy. The films consist of well-developed grains of rectangular shape, in the following called tiles. The boundaries between the tiles are strained and contain many defects. A new, specific type of lattice defect is found in the tile boundaries. This defect is de-scribed as a staircase formed by repeated lattice shifts of Delta ~ c_t/12 ~ 4.2 Å in the [001] direction, which result in seemingly bent ribbons of stacked Bi₂O₂ planes. The individual Bi₂O₂ planes remain, however, strongly parallel to the (001) plane. Each step of the staircase being formed by short sections of two or more Bi₂O₂ layers in direct con-tact, the defects carry a bismuth excess. Accordingly, the tile bounda-ries are bismuth-rich. A model to explain this bismuth excess of the tile boundaries is proposed.

Keywords: lattice defects, Aurivillius-type structures, ferroelectric films, epitaxy, Ba2Bi4Ti5O18, transmission electron microscopy

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