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Characterization

Combining diffraction theory with electronic-structure theory of solids to decode electron-energy-loss spectra


Top: Two dimensional simulation of the separation of two peaks in the O K-shell spectrum as a function of probe position. Bottom: A line scan, diagonally across the unit cell (inset) as indicated by the black arrow. The corresponding experimental values are shown by the red circles.

A theory combining both a material’s electronic structure and electron beam propagation has been developed at Vanderbilt University in conjunction with experimental data obtained at Oak Ridge National Laboratory. Aberration-corrected scanning transmission electron microscopy probes atomic and electronic properties of complex materials structures with unprecedented spatial resolution via electron-energy-loss spectroscopy. The near-edge structure in core-loss spectra reflects the available local electronic states.

In order to understand the variation in experimental spectra, calculations must include two main ingredients: diffraction theory describing the evolution of the electron beam in the material and solid-state electronic structure theory that describes the excitation process.

The figure shows the simulated spatial variation of the distance between two main features of the O K-shell spectrum in LaMnO3.  The line scan across the diagonal of the unit cell shows contrast in close agreement with the experimental measurements indicated by the red circles.  The new capability offers an enormous potential to decode data and extract detailed information on local electronic properties in complex materials systems such as interfaces, defects, and ordered vacancies.

M. P. Prange, M. P. Oxley, M. Varela, S. J. Pennycook, and S. T. Pantelides, “Simulation of spatially resolved electron energy loss near-edge structure for scanning transmission electron microscopy,” Phys. Rev. Lett. 109, 246101 (2012).  DOI: 10.1103/PhysRevLett.109.246101

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