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Strain Localization in Thin Films of Bi(Fe,Mn)O3 Due to the Formation of Stepped Mn(4+)-Rich Antiphase Boundaries.

MacLaren I, Sala B, Andersson SM, Pennycook TJ, Xiong J, Jia QX, Choi EM, MacManus-Driscoll JL - Nanoscale Res Lett (2015)

Bottom Line: These have the effect of confining the material below the pyramids in a highly strained state with an out-of-plane lattice parameter close to 4.1 Å.Outside the area enclosed by the antiphase boundaries, the out-of-plane lattice parameter is much closer to bulk values for BFMO.Since the antiphase boundaries seem to form from the interaction of Mn with the Ti in the substrate, one route to perform this would be to grow a thin buffer layer of pure BiFeO3 on the SrTiO3 substrate to minimise any Mn-Ti interactions.

View Article: PubMed Central - PubMed

Affiliation: SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK. ian.maclaren@glasgow.ac.uk.

ABSTRACT
The atomic structure and chemistry of thin films of Bi(Fe,Mn)O3 (BFMO) films with a target composition of Bi2FeMnO6 on SrTiO3 are studied using scanning transmission electron microscopy imaging and electron energy loss spectroscopy. It is shown that Mn(4+)-rich antiphase boundaries are locally nucleated right at the film substrate and then form stepped structures that are approximately pyramidal in three dimensions. These have the effect of confining the material below the pyramids in a highly strained state with an out-of-plane lattice parameter close to 4.1 Å. Outside the area enclosed by the antiphase boundaries, the out-of-plane lattice parameter is much closer to bulk values for BFMO. This suggests that to improve the crystallographic perfection of the films whilst retaining the strain state through as much of the film as possible, ways need to be found to prevent nucleation of the antiphase boundaries. Since the antiphase boundaries seem to form from the interaction of Mn with the Ti in the substrate, one route to perform this would be to grow a thin buffer layer of pure BiFeO3 on the SrTiO3 substrate to minimise any Mn-Ti interactions.

No MeSH data available.


Related in: MedlinePlus

Atomic resolution chemical maps of a stepped region of an antiphase boundary. a Survey image. b Composite image of Fe (red), HAADF signal (purple) and Mn signal (green). c Composite image showing the Mn3+ (lilac) and Mn4+ (pink) MLLS fits. d Standard spectra used for this MLLS fit
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Fig4: Atomic resolution chemical maps of a stepped region of an antiphase boundary. a Survey image. b Composite image of Fe (red), HAADF signal (purple) and Mn signal (green). c Composite image showing the Mn3+ (lilac) and Mn4+ (pink) MLLS fits. d Standard spectra used for this MLLS fit

Mentions: Figure 4 shows atomic resolution chemical maps of a stepped area of the APB showing that, whilst Fe is present both in B-sites in the surrounding perovskite and in the boundary, Mn is strongly segregated to the B-sites in the boundary. It was clear from studying the EEL spectra from this spectrum image, as shown in Fig. 3d, that the Mn white lines were shifting and changing shape between the perovskite and the boundary, suggesting that the oxidation state is changing. The trends are much like those seen previously by Garvie and Craven [25], whereby the edge onset moves to higher energy with increasing oxidation state, with a concurrent decrease in the L3:L2 ratio, as later used by Wang et al. and others [26–28] for measuring Mn oxidation states. Mapping using the L3:L2 ratio was used by Choi et al. [13] to show a change of Mn oxidation state in these films from Mn3+ in the perovskite to Mn4+ on the interface to the SrTiO3. In the current work, MLLS fitting was used to treat a background-subtracted Mn edge spectrum image of this area (640–665 eV energy loss) as a linear sum of two extreme components, one from the matrix and another from the step in the boundary. The former must be Mn3+ in accord with Choi et al. [13], and the latter was believed to be close to Mn4+. The results are shown in Fig. 3c which clearly show that all the Mn in the boundary steps oxidises to Mn4+.Fig. 4


Strain Localization in Thin Films of Bi(Fe,Mn)O3 Due to the Formation of Stepped Mn(4+)-Rich Antiphase Boundaries.

MacLaren I, Sala B, Andersson SM, Pennycook TJ, Xiong J, Jia QX, Choi EM, MacManus-Driscoll JL - Nanoscale Res Lett (2015)

Atomic resolution chemical maps of a stepped region of an antiphase boundary. a Survey image. b Composite image of Fe (red), HAADF signal (purple) and Mn signal (green). c Composite image showing the Mn3+ (lilac) and Mn4+ (pink) MLLS fits. d Standard spectra used for this MLLS fit
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig4: Atomic resolution chemical maps of a stepped region of an antiphase boundary. a Survey image. b Composite image of Fe (red), HAADF signal (purple) and Mn signal (green). c Composite image showing the Mn3+ (lilac) and Mn4+ (pink) MLLS fits. d Standard spectra used for this MLLS fit
Mentions: Figure 4 shows atomic resolution chemical maps of a stepped area of the APB showing that, whilst Fe is present both in B-sites in the surrounding perovskite and in the boundary, Mn is strongly segregated to the B-sites in the boundary. It was clear from studying the EEL spectra from this spectrum image, as shown in Fig. 3d, that the Mn white lines were shifting and changing shape between the perovskite and the boundary, suggesting that the oxidation state is changing. The trends are much like those seen previously by Garvie and Craven [25], whereby the edge onset moves to higher energy with increasing oxidation state, with a concurrent decrease in the L3:L2 ratio, as later used by Wang et al. and others [26–28] for measuring Mn oxidation states. Mapping using the L3:L2 ratio was used by Choi et al. [13] to show a change of Mn oxidation state in these films from Mn3+ in the perovskite to Mn4+ on the interface to the SrTiO3. In the current work, MLLS fitting was used to treat a background-subtracted Mn edge spectrum image of this area (640–665 eV energy loss) as a linear sum of two extreme components, one from the matrix and another from the step in the boundary. The former must be Mn3+ in accord with Choi et al. [13], and the latter was believed to be close to Mn4+. The results are shown in Fig. 3c which clearly show that all the Mn in the boundary steps oxidises to Mn4+.Fig. 4

Bottom Line: These have the effect of confining the material below the pyramids in a highly strained state with an out-of-plane lattice parameter close to 4.1 Å.Outside the area enclosed by the antiphase boundaries, the out-of-plane lattice parameter is much closer to bulk values for BFMO.Since the antiphase boundaries seem to form from the interaction of Mn with the Ti in the substrate, one route to perform this would be to grow a thin buffer layer of pure BiFeO3 on the SrTiO3 substrate to minimise any Mn-Ti interactions.

View Article: PubMed Central - PubMed

Affiliation: SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK. ian.maclaren@glasgow.ac.uk.

ABSTRACT
The atomic structure and chemistry of thin films of Bi(Fe,Mn)O3 (BFMO) films with a target composition of Bi2FeMnO6 on SrTiO3 are studied using scanning transmission electron microscopy imaging and electron energy loss spectroscopy. It is shown that Mn(4+)-rich antiphase boundaries are locally nucleated right at the film substrate and then form stepped structures that are approximately pyramidal in three dimensions. These have the effect of confining the material below the pyramids in a highly strained state with an out-of-plane lattice parameter close to 4.1 Å. Outside the area enclosed by the antiphase boundaries, the out-of-plane lattice parameter is much closer to bulk values for BFMO. This suggests that to improve the crystallographic perfection of the films whilst retaining the strain state through as much of the film as possible, ways need to be found to prevent nucleation of the antiphase boundaries. Since the antiphase boundaries seem to form from the interaction of Mn with the Ti in the substrate, one route to perform this would be to grow a thin buffer layer of pure BiFeO3 on the SrTiO3 substrate to minimise any Mn-Ti interactions.

No MeSH data available.


Related in: MedlinePlus