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Measurement Error in Atomic-Scale Scanning Transmission Electron Microscopy—Energy-Dispersive X-Ray Spectroscopy (STEM-EDS) Mapping of a Model Oxide Interface

Published online by Cambridge University Press:  05 April 2017

Steven R. Spurgeon Open the ORCID record for Steven R. Spurgeon [Opens in a new window] ,
Yingge Du  and
Scott A. Chambers
Steven R. Spurgeon
Affiliation:
Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
Yingge Du
Affiliation:
Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
Scott A. Chambers*
Affiliation:
Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
*
*Corresponding author. sa.chambers@pnnl.gov
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Abstract

With the development of affordable aberration correctors, analytical scanning transmission electron microscopy (STEM) studies of complex interfaces can now be conducted at high spatial resolution at laboratories worldwide. Energy-dispersive X-ray spectroscopy (EDS) in particular has grown in popularity, as it enables elemental mapping over a wide range of ionization energies. However, the interpretation of atomically resolved data is greatly complicated by beam–sample interactions that are often overlooked by novice users. Here we describe the practical factors—namely, sample thickness and the choice of ionization edge—that affect the quantification of a model perovskite oxide interface. Our measurements of the same sample, in regions of different thickness, indicate that interface profiles can vary by as much as 2–5 unit cells, depending on the spectral feature. This finding is supported by multislice simulations, which reveal that on-axis maps of even perfectly abrupt interfaces exhibit significant delocalization. Quantification of thicker samples is further complicated by channeling to heavier sites across the interface, as well as an increased signal background. We show that extreme care must be taken to prepare samples to minimize channeling effects and argue that it may not be possible to extract atomically resolved information from many chemical maps.

Keywords

STEMEDSmultisliceoxidesinterfaces
Type
Materials Science Applications
Information
Microscopy and Microanalysis , Volume 23 , Issue 3 , June 2017 , pp. 513 - 517
Copyright
© Microscopy Society of America 2017 

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