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Quantitative Chemical Mapping of InGaN Quantum Wells from Calibrated High-Angle Annular Dark Field Micrographs

Published online by Cambridge University Press:  30 June 2015

Daniel Carvalho ,
Francisco M. Morales ,
Teresa Ben ,
Rafael García ,
Andrés Redondo-Cubero ,
Eduardo Alves ,
Katharina Lorenz ,
Paul R. Edwards ,
Kevin P. O’Donnell  and
Christian Wetzel
Daniel Carvalho*
Affiliation:
Departamento de Ciencia de los Materiales e I. M. y Q. I., Facultad de Ciencias, Universidad de Cádiz, Cádiz, Spain IMEYMAT: Institute of Research on Electron Microscopy and Materials of the University of Cádiz, Spain
Francisco M. Morales
Affiliation:
Departamento de Ciencia de los Materiales e I. M. y Q. I., Facultad de Ciencias, Universidad de Cádiz, Cádiz, Spain IMEYMAT: Institute of Research on Electron Microscopy and Materials of the University of Cádiz, Spain
Teresa Ben
Affiliation:
Departamento de Ciencia de los Materiales e I. M. y Q. I., Facultad de Ciencias, Universidad de Cádiz, Cádiz, Spain IMEYMAT: Institute of Research on Electron Microscopy and Materials of the University of Cádiz, Spain
Rafael García
Affiliation:
Departamento de Ciencia de los Materiales e I. M. y Q. I., Facultad de Ciencias, Universidad de Cádiz, Cádiz, Spain IMEYMAT: Institute of Research on Electron Microscopy and Materials of the University of Cádiz, Spain
Andrés Redondo-Cubero
Affiliation:
IPFN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, km 139.7, 2695-066 Bobadela LRS, Portugal Departamento de Física Aplicada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
Eduardo Alves
Affiliation:
IPFN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, km 139.7, 2695-066 Bobadela LRS, Portugal
Katharina Lorenz
Affiliation:
IPFN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, km 139.7, 2695-066 Bobadela LRS, Portugal
Paul R. Edwards
Affiliation:
SUPA Department of Physics, University of Strathclyde, Glasgow, G4 0NG, Scotland, UK
Kevin P. O’Donnell
Affiliation:
SUPA Department of Physics, University of Strathclyde, Glasgow, G4 0NG, Scotland, UK
Christian Wetzel
Affiliation:
Department of Physics and Future Chips Constellation, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
*
*Corresponding author. [email protected]
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Abstract

We present a simple and robust method to acquire quantitative maps of compositional fluctuations in nanostructures from low magnification high-angle annular dark field (HAADF) micrographs calibrated by energy-dispersive X-ray (EDX) spectroscopy in scanning transmission electron microscopy (STEM) mode. We show that a nonuniform background in HAADF-STEM micrographs can be eliminated, to a first approximation, by use of a suitable analytic function. The uncertainty in probe position when collecting an EDX spectrum renders the calibration of HAADF-STEM micrographs indirect, and a statistical approach has been developed to determine the position with confidence. Our analysis procedure, presented in a flowchart to facilitate the successful implementation of the method by users, was applied to discontinuous InGaN/GaN quantum wells in order to obtain quantitative determinations of compositional fluctuations on the nanoscale.

Keywords

InGaNHAADF-STEMEDXRBSchemical quantification
Type
Materials Applications and Techniques
Information
Microscopy and Microanalysis , Volume 21 , Issue 4 , August 2015 , pp. 994 - 1005
Copyright
© Microscopy Society of America 2015 

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