Direct Determination of Grain Boundary Atomic Structure in SrTiO
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McGibbon, M. M.; Browning, Nigel D.; Chisholm, M. F.; McGibbon, A. J.; Pennycook, Stephen J.; Ravikumar, V.; Dravid, Vinayak P.

doi:10.1126/science.266.5182.102

Cited by 182 publications

(63 citation statements)

References 24 publications

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“…A (030.2) A dilatation normal to the boundary plane was measured in this asymmetric facet [58]. This is consistent with a dilatation of (0.6k0.2) A [35] in the symmetric portion of the boundary, and is to be expected since any dilatation of the short asymmetric facet is necessarily constrained by the dilatation of the symme~c regions predominant in this boundary. As before the cation coordinates…”

Section: Asymmetric Grain Boundariessupporting

confidence: 65%

“…This increase in angle accompanied by a decrease in accelerating potential was found to significantly decrease the amount of ion-milling damage to the specimen. Figure 6 shows the maximum entropy object function for a 25' ( E 8 S ) symmetric (920) boundary in a SrTiQ bicrystal [35]. Energy loss spectra taken from the bulk and boundary are shown in figure 7.…”

Section: Experimental Characterization Of [Ool] Tiit Grain Boundariesmentioning

confidence: 99%

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Direct experimental determination of the atomic structure at internal interfaces

Browning

Pennycook

1996

J. Phys. D: Appl. Phys.

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A crucial first step in understanding the effect that internal interfaces have on the properties of materials is the ability to determine the atomic structure at the interface. As interfaces can contain atomic disorder, dislocations, segregated impurities and interphases, sensitivity to all of these features is essential for complete experimental characterization. By combining Z-contrast imaging and electron energy loss spectroscopy (EELS) in a dedicated scanning transmission electron microscope (STEM), the ability to probe the structure, bonding and composition at interfaces with the necessary atomic resolution has been obtained. Experimental conditions can be controlled to provide, simultaneously, both incoherent imaging and spectroscopy. This enables interface structures observed in the image to be interpreted intuitively and the bonding in a specified atomic column to be probed directly by EELS. The bonding and structure information can then be correlated using bond-valence sum analysis to produce structural models. This technique is demonstrated for 25", 36" and 67" symmetric and 45" and 25" asymmetric [Ool] tilt grain boundaries in SrTiO,. The structures of both types of boundary were found to contain partially occupied columns in the boundary plane. From these experimental results, a series of structural units were identified which could be combined, using continuity of grain boundary structure principles, to construct all [Ool] tilt boundaries in SrTiO,. Using these models, the ability of this technique to address the issues of vacancies and dopant segregation at grain boundaries in electroceramics is discussed. %e submitted manuscript has been authored by a contractor of the U.S.

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Section: Asymmetric Grain Boundariessupporting

confidence: 65%

Section: Experimental Characterization Of [Ool] Tiit Grain Boundariesmentioning

confidence: 99%

Direct experimental determination of the atomic structure at internal interfaces

Browning

Pennycook

1996

J. Phys. D: Appl. Phys.

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“…Examples of such studies include the work of Browning et al 70 and McGibbon et al 71 on grain boundaries in YBa 2 Cu 3 O 7-x high T C superconductors and SrTiO 3 , respectively. In this work, qualitative matching of atomic-resolution images to theoretically predicted structures was used to verify the theoretical predictions.…”

Section: Application Of Ac-stem To Functional Oxidesmentioning

confidence: 99%

Aberration-corrected scanning transmission electron microscopy for atomic-resolution studies of functional oxides

MacLaren

Ramasse

2014

International Materials Reviews

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Electron microscopy has undergone a major revolution in the past few years because of the practical implementation of correctors for the parasitic lens aberrations that otherwise limit resolution. This has been particularly significant for scanning transmission electron microscopy (STEM) and now allows electron beams to be produced with a spot size of well below 1 Å , sufficient to resolve inter-atomic spacings in most crystal structures. This means that the advantages of STEM, relatively straightforward interpretation of images and highly localised analysis through electron energy-loss spectroscopy, can now be applied with atomic resolution to all kinds of materials and nanostructures. As this review shows, this is revolutionising our understanding of functional oxide ceramics, thin films, heterostructures and nanoparticles. This includes quantitative analysis of structures with picometre precision, mapping of electric polarisation at the unit cell scale, and mapping of chemistry and bonding on an atom-by-atom basis. This is also now providing the kind of high quality data that are very complementary to density functional theory (DFT) modelling, and combined DFT/microscopy studies are now providing deep insights into the structure and electronic structure of oxide nanostructures. Finally, some suggestions are made as to the prospects for further advances in our atomistic understanding of such materials as a consequence of recent technical advances in spectroscopy and imaging.

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“…The geometric structure of SrTiOJ grain boundaries has been obtained from Z-contrast STEM images [7][8][9]. The dark field image obtained from a high angle annular detector is incoherent, so the image is described as convolution of the atomic scattering cross section with the STEM probe profile, which allows direct location of atomic columns from the image without extra simulations.…”

Section: Methodsmentioning

confidence: 99%

Z-Contrast STEM Imaging and Ab-Initio Calculations of Grain Boundaries in SrTiO₃

et al. 1999

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The understanding of electrical properties of grain boundaries in perovskites is essential for their application to capacitors, varistors and positive-temperature coefficient resistors. The origin of the electrical activity is generally attributed to the existence of charged defects in grain boundaries, usually assumed to be impurities, which setup a double Schottky barrier as they are screened by dopants in the adjacent bulk crystal. Microscopic understanding of the origin of the grain boundary charge, however, has not been achieved. It is not known yet if the charged grain boundary states are an intrinsic property of a stoichiometric grain boundary, arise from nonstoichiometry, or are caused by impurities. Here, the relation between atomic structure and electronic properties is studied by combining experiment with ab-initio calculations. The starting structures for theoretical calculations were obtained from Z-contrast images combined with electron energy loss spectroscopy to resolve the dislocation core structures comprising the boundary. Dislocation core reconstructions are typical of all grain boundaries so far observed in this material. They avoid like-ion repulsion, and provide alternative sites for cation occupation in the groin boundaries. Optimized atomic positions are found by total energy calculations. Calculated differences in vacancy formation energies between the grain boundaries and the bulk suggest that vacancy segregation can account for the postulated grain boundary charge.

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Direct Determination of Grain Boundary Atomic Structure in SrTiO ₃

Cited by 182 publications

References 24 publications

Direct experimental determination of the atomic structure at internal interfaces

Direct experimental determination of the atomic structure at internal interfaces

Aberration-corrected scanning transmission electron microscopy for atomic-resolution studies of functional oxides

Z-Contrast STEM Imaging and Ab-Initio Calculations of Grain Boundaries in SrTiO₃

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Direct Determination of Grain Boundary Atomic Structure in SrTiO 3

Cited by 182 publications

References 24 publications

Direct experimental determination of the atomic structure at internal interfaces

Direct experimental determination of the atomic structure at internal interfaces

Aberration-corrected scanning transmission electron microscopy for atomic-resolution studies of functional oxides

Z-Contrast STEM Imaging and Ab-Initio Calculations of Grain Boundaries in SrTiO3

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Product

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Direct Determination of Grain Boundary Atomic Structure in SrTiO ₃

Z-Contrast STEM Imaging and Ab-Initio Calculations of Grain Boundaries in SrTiO₃