Atomic Structure of Highly Strained<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>BiFeO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>Thin Films

Rossell, Marta D.; Erni, Rolf; Prange, Micah P.; Idrobo, Juan Carlos; Luo, Wenjin; Zeches, R. J.; Pantelides, Sokrates T.; Ramesh, R.

doi:10.1103/physrevlett.108.047601

Cited by 99 publications

(97 citation statements)

References 34 publications

(47 reference statements)

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“…At large compressive strains, the octahedral rotations along the c ‐axis are completely frozen and an a − b − c 0 tilt pattern is obtained for the optimized structure. Contrary to previous calculations that only imposed an inplane strain,6, 8 when we impose the experimentally observed structural parameters ( b / a ratio and shear angle β ), we retain a lower P 1 symmetry than the previously reported predictions of Cc or Pm phases 8, 17, 18. This space group determination was performed using the FINDSYM19 software.…”

Section: Resultsmentioning

confidence: 98%

Understanding Strain‐Induced Phase Transformations in BiFeO₃ Thin Films

et al. 2015

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Experiments demonstrate that under large epitaxial strain a coexisting striped phase emerges in BiFeO3 thin films, which comprises a tetragonal‐like (T′) and an intermediate S′ polymorph. It exhibits a relatively large piezoelectric response when switching between the coexisting phase and a uniform T′ phase. This strain‐induced phase transformation is investigated through a synergistic combination of first‐principles theory and experiments. The results show that the S′ phase is energetically very close to the T′ phase, but is structurally similar to the bulk rhombohedral (R) phase. By fully characterizing the intermediate S′ polymorph, it is demonstrated that the flat energy landscape resulting in the absence of an energy barrier between the T′ and S′ phases fosters the above‐mentioned reversible phase transformation. This ability to readily transform between the S′ and T′ polymorphs, which have very different octahedral rotation patterns and c/a ratios, is crucial to the enhanced piezoelectricity in strained BiFeO3 films. Additionally, a blueshift in the band gap when moving from R to S′ to T′ is observed. These results emphasize the importance of strain engineering for tuning electromechanical responses or, creating unique energy harvesting photonic structures, in oxide thin film architectures.

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Section: Resultsmentioning

confidence: 98%

Understanding Strain‐Induced Phase Transformations in BiFeO₃ Thin Films

et al. 2015

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“…Within the Fe L 2,3 edge shown in Figure 3(j), no shoulder on the low energy side of the L 3 white line is observed, which occurs due to octahedral crystal field splitting, particularly for Fe 3+ , 12 including in rhombohedral BiFeO 3 , 13 although not for more symmetric structures such as the supertetragonal T-phase. 13 Moreover, there is no detectable change in this ELNES between the perovskite and the step, which would suggest that the Fe is in the same 3+ oxidation state in the step as in the surrounding matrix.…”

Section: -mentioning

confidence: 99%

“…13 Moreover, there is no detectable change in this ELNES between the perovskite and the step, which would suggest that the Fe is in the same 3+ oxidation state in the step as in the surrounding matrix. Moreover, it suggests that the ions in the step are very similarly octahedrally coordinated at the steps as in the perovskite matrix.…”

Section: -mentioning

confidence: 99%

“…Such a high charge density would be expected to result in strong polarisation around the steps, which is indeed observed with noticeable movement of O columns away from the steps, Bi columns towards the steps, and large pseudotetragonal distortion of the cells to something analogous to the supertetragonal T-phase. 4,13,16 Of course, one final feature of interest is why these stepped boundaries are formed. Clearly, the Ti-rich planar sections will have been formed by self-assembly during sintering in Ti-rich regions of the sample.…”

Section: -mentioning

confidence: 99%

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The atomic structure and chemistry of Fe-rich steps on antiphase boundaries in Ti-doped Bi0.9Nd0.15FeO3

et al. 2014

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Stepped antiphase boundaries are frequently observed in Ti-doped Bi0.85Nd0.15FeO3, related to the novel planar antiphase boundaries reported recently. The atomic structure and chemistry of these steps are determined by a combination of high angle annular dark field and bright field scanning transmission electron microscopy imaging, together with electron energy loss spectroscopy. The core of these steps is found to consist of 4 edge-sharing FeO6 octahedra. The structure is confirmed by image simulations using a frozen phonon multislice approach. The steps are also found to be negatively charged and, like the planar boundaries studied previously, result in polarisation of the surrounding perovskite matrix.

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“…4,5 This reported superior polarization may originate from the off-centering shift of cation in the highly distorted phase. 6 On the other hand, bulk BFO also exhibits a G-type antiferromagnetic order under Neél temperature 640K, where Fe magnetic moments are aligned ferromagnetically in the pseudo-cubic (111) planes and anti-ferromagnetically between adjacent planes. 7 Superimposed on the anti-ferromagnetic order, there is a long-range spiral cycloid modulation with a period of ∼ 62 nm for bulk BFO.…”

Section: Introductionmentioning

confidence: 99%

Epitaxial growth of BiFeO3 films on TiN under layers by sputtering deposition

Wang

et al. 2017

AIP Advances

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BiFeO3/TiN/MgO (001) films have been prepared by magneton sputtering, where TiN serves as a conductive under layer. X-ray diffraction profiles and cross-sectional transmission electron microscopy images reveal that not only (001)-epitaxial BiFeO3 films are obtained, but also both tetragonal and rhombohedral phases co-exist in BiFeO3 films. Their crystallographic relationship is shown as following: tetragonal-BiFeO3 (001) [100]//TiN (001) [100]//MgO (001) [100] and rhombohedral-BiFeO3 (001) [100]//TiN (001) [100]//MgO (001) [100]. Besides, an oxidized TiN layer (∼ 20 nm) has also been detected between BiFeO3 and TiN layers and its formation may originate from oxygen inter-diffusion from BiFeO3 layer. Despite of the existence of the oxidized TiN layer, it does not affect the epitaxial growth of BiFeO3 films. On the other hand, the coercivity electric field obtained in ferroelectric loop of BiFeO3 is greatly enhanced to 49 MV/cm due to the existence of oxidized TiN layer.

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Atomic Structure of Highly StrainedBiFeO3Thin Films

Cited by 99 publications

References 34 publications

Understanding Strain‐Induced Phase Transformations in BiFeO₃ Thin Films

Understanding Strain‐Induced Phase Transformations in BiFeO₃ Thin Films

The atomic structure and chemistry of Fe-rich steps on antiphase boundaries in Ti-doped Bi0.9Nd0.15FeO3

Epitaxial growth of BiFeO3 films on TiN under layers by sputtering deposition

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Atomic Structure of Highly StrainedBiFeO3Thin Films

Cited by 99 publications

References 34 publications

Understanding Strain‐Induced Phase Transformations in BiFeO3 Thin Films

Understanding Strain‐Induced Phase Transformations in BiFeO3 Thin Films

The atomic structure and chemistry of Fe-rich steps on antiphase boundaries in Ti-doped Bi0.9Nd0.15FeO3

Epitaxial growth of BiFeO3 films on TiN under layers by sputtering deposition

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Understanding Strain‐Induced Phase Transformations in BiFeO₃ Thin Films

Understanding Strain‐Induced Phase Transformations in BiFeO₃ Thin Films