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Chemical mapping at atomic resolution using energy-dispersive x-ray spectroscopy

Published online by Cambridge University Press:  13 January 2012

Leslie J. Allen
Affiliation:
School of Physics, University of Melbourne; lja@unimelb.edu.au
Adrian J. D’Alfonso
Affiliation:
School of Physics, University of Melbourne; adrian@dalfonso.com.au
Bert Freitag
Affiliation:
FEI Company, The Netherlands; Bert.Freitag@fei.com
Dmitri O. Klenov
Affiliation:
FEI Company, The Netherlands; Dmitri.O.Klenov@fei.com
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Abstract

We review the recently introduced technique of atomic-resolution chemical mapping in scanning transmission electron microscopy (STEM) based on energy-dispersive x-ray spectroscopy. Working at the atomic level is facilitated by ultrasensitive energy-dispersive x-ray detectors in combination with Cs-correction of the STEM probe. Details of the experimental implementation are discussed, and a theoretical framework within which the measured results can be understood is described. Three case studies are presented: the analysis of specimens of GaAs and SrTiO3, as well as examination of an interface between SrTiO3 and PbTiO3. Detailed theoretical simulations of the imaging process show that the projected positions of elements in atomic columns can be directly deduced from the chemical maps. For the core shells used, the effective ionization interaction is local and generally localized in the vicinity of the atoms being ionized. The local nature of the effective ionization potential means that this is an incoherent mode of imaging, akin to Z-contrast imaging but with additional chemical information.

Type
Research Article
Copyright
Copyright © Materials Research Society 2012

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