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Technique Recovers Atomic Resolution in Spectrum Images

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Raw Fe L-shell spectrum image data, which indicate magnetic properties of the material, were acquired using scanning transmission electron microscopy (left). Recovered atomic signals are shown after removing the effects of electron scattering (right).
Researchers have demonstrated a technique for obtaining atomic-resolution information from spectrum images of thick specimens of MnFePSi compounds, which are promising for ecofriendly refrigeration. This technique allows the quantitative examination of specimens for which atomic-resolution spectroscopic analysis was previously impossible.

In thin specimens in contrast, aberration-corrected scanning transmission electron microscopy (STEM) has made the acquisition of atomic-resolution images based on electron energy loss spectroscopy (EELS) possible. In thicker specimens, however, as the probe electrons propagate through the crystal they become increasingly delocalized, leading to a loss of atomic resolution in the collected spectroscopy data. But many materials are not amenable to the preparation techniques required to produce suitably thin specimens.  In addition, thin specimens may exhibit properties not observed in the bulk materials used in functional devices.  This technique, which combines scattering theory with detailed quantification of microscope parameters, provides not only unambiguous identification of local compositions, but also enhanced details of electronic properties from individual locations in both thin and thick specimens, leading to a greater understanding of materials’ properties.

 

Melissa J. Neish, Mark P. Oxley, Junjie Guo, Brian C. Sales, Leslie J. Allen, and Matthew F. Chisholm, “Local Observation of the Site Occupancy of Mn in a MnFePSi Compound,” Phys. Rev. Lett. 114, 106101 (2015).  doi: 10.1103/PhysRevLett.114.106101

 

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