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Title: Model-independent measurement of the charge density distribution along an Fe atom probe needle using off-axis electron holography without mean inner potential effects

The one-dimensional charge density distribution along an electrically biased Fe atom probe needle is measured using a model-independent approach based on off-axis electron holography in the transmission electron microscope. Both the mean inner potential and the magnetic contribution to the phase shift are subtracted by taking differences between electron-optical phase images recorded with different voltages applied to the needle. The measured one-dimensional charge density distribution along the needle is compared with a similar result obtained using model-based fitting of the phase shift surrounding the needle. On the assumption of cylindrical symmetry, it is then used to infer the three-dimensional electric field and electrostatic potential around the needle with ∼10 nm spatial resolution, without needing to consider either the influence of the perturbed reference wave or the extension of the projected potential outside the field of view of the electron hologram. The present study illustrates how a model-independent approach can be used to measure local variations in charge density in a material using electron holography in the presence of additional contributions to the phase, such as those arising from changes in mean inner potential and specimen thickness.
Authors:
;  [1] ;  [2] ;  [3]
  1. Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C) and Peter Grünberg Institute (PGI), Forschungszentrum Jülich, D-52425 Jülich (Germany)
  2. Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)
  3. Fakultät für Physik and Center of Nanointegration (CeNIDE), Universität Duisburg-Essen, D-47048 Duisburg (Germany)
Publication Date:
OSTI Identifier:
22399392
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 13; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ATOMS; CHARGE DENSITY; COMPARATIVE EVALUATIONS; CYLINDRICAL CONFIGURATION; ELECTRIC FIELDS; ELECTRIC POTENTIAL; ELECTRONS; HOLOGRAPHY; IMAGES; IRON; ONE-DIMENSIONAL CALCULATIONS; PHASE SHIFT; POTENTIALS; PROBES; SPATIAL RESOLUTION; SYMMETRY; THREE-DIMENSIONAL CALCULATIONS; TRANSMISSION ELECTRON MICROSCOPY; VARIATIONS