Correlative Atom probe tomography
PRL 113, 035501 (2014) PHYSICAL REVIEW LETTERS
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Acta Materialia 80 (2014) 94–106
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What is correlative electron microscopy and atom probe tomography ?
The correlative use of electron microscopy and atom probe tomography describe an experimental probing methodology which aims at revealing both, all relevant structural features and the chemical
composition at exactly the same material position in three dimensions at full atomic scale at ppm chemcial precision. This method is also sometimes referred to as correlative atom probe
Typically the method works by preparing needle shaped tips with a tip apex radius of around 50 nm that are suited for atom probe tomography, yet, before doing so these tips are first exposed to electron microscopical observations.
Then the two data sets from electron microscopy and atom probe tomography or jointly analysed.
Currently this combination of methods applied to exactly the same material portion represents the highest resolving joint crystallographic and chemical analysis method that can be applied to materials in 3D.
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Why is correlative electron microscopy and atom probe tomography important ?
Using correlative electron microscopy and atom probe tomography enables us to reveal complex structural phenomena in materials and their interplay with chemical features. Most structural effects in complex modern materials, be at the formation of certain phases or the vast hierarchy of different types of lattice defects such as point defects, dislocations, grain boundaries or hetero-phase interfaces are characterized by specific chemical features. Therefore a more holistic understanding of nanostructured materials requires to reveal both, the local chemical composition together with the local structure of phases and defects to highest possible resolution in three dimensions.
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Acta Materialia 84 (2015) 110–123
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Acta Materialia 59 (2011) 3965–3977
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What is the advantage of correlative electron microscopy and atom probe tomography compared to crystallographic atom probe tomography ?
Crystallographic atom probe refers to a method where some of the lattice planes can be resolved without the use of electron microscopy only through the adequate analysis of field desorption poles
of crystallographic nature from atom probe tomography directly.
However, different from electron microscopy in many atom probe tomographic experiments only some of the lattice planes can be resolved so that typically a full local crystallographic analysis is not always possible.
Therefore a combined application of electron microscopy and atom probe tomography to the same sample region gives a more complete structural analysis then using crystallographic atom probe tomography alone.
Can we coupled also high resolution electron microscopy with atom probe tomography ?
Atom probe tomography can also be directly coupled with high resolution electron microscopy to resolve discrete atomic columns. The reason for this is that the needle shaped tips that are produced by using focused ion beam method for instance are so thin so that scanning transmission electron microscopy can resolve the atomic columns in such atom probe specimens prior to evaporation. Therefore atom probe tomography can be at the same region of interest directly combined with atomically resolving scanning transmission electron microscopy for resolving structural features in concert with chemical features at atomic scale.