Designer defect stabilization of the super tetragonal phase in >70-nm-thick BiFeO3 films on LaAlO3 substrates

Daniel Sando, Thomas Young, Ralph Bulanadi, Xuan Cheng, Yanyu Zhou, Matthew Weyland, Paul Munroe, Valanoor Nagarajan

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The stability of the “T-like” (T$) phase in BiFeO3 films grown on LaAlO3(001) is investigated. We show that the T$ phase can be stabilized for thicknesses >70nm under ultralow incident flux conditions in pulsed laser ablation growth. This low flux results in a low growth rate; thus, the sample is held at high temperatures (>600°C) for much longer than is typical. Transmission electron microscopy and X-ray diffraction analysis suggest that such growth conditions favor the formation of nanoscale “defect pockets”, which apply a local compressive strain of >1.8%. We propose that the cumulative effect of local stresses induced by such “designer defects” maintains macroscale strain coherence mechanical boundary conditions, which then preserves the T$ phase to thicknesses beyond conventional wisdom. Finally, by intentionally introducing an amorphous phase at the film-substrate interface, it is shown that the mixed-phase proportion can be tuned for a given thickness.

Original languageEnglish
Article number0902B2
Number of pages7
JournalJapanese Journal of Applied Physics
Issue number9
Publication statusPublished - 1 Sept 2018

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