skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Towards quantitative off-axis electron holographic mapping of the electric field around the tip of a sharp biased metallic needle

Abstract

We apply off-axis electron holography and Lorentz microscopy in the transmission electron microscope to map the electric field generated by a sharp biased metallic tip. A combination of experimental data and modelling provides quantitative information about the potential and the field around the tip. Close to the tip apex, we measure a maximum field intensity of 82 MV/m, corresponding to a field k factor of 2.5, in excellent agreement with theory. In order to verify the validity of the measurements, we use the inferred charge density distribution in the tip region to generate simulated phase maps and Fresnel (out-of-focus) images for comparison with experimental measurements. While the overall agreement is excellent, the simulations also highlight the presence of an unexpected astigmatic contribution to the intensity in a highly defocused Fresnel image, which is thought to result from the geometry of the applied field.

Authors:
 [1];  [2];  [1]; ;  [3];  [4];  [5]
  1. Center for Electron Nanoscopy, Technical University of Denmark, Kongens Lyngby (Denmark)
  2. (Germany)
  3. CAMECA Instruments, Inc., Madison, Wisconsin 53711 (United States)
  4. Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungzentrum Jülich, Jülich (Germany)
  5. Department of Physics and Astronomy, University of Bologna, Bologna (Italy)
Publication Date:
OSTI Identifier:
22308977
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 2; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CHARGE DENSITY; DISTRIBUTION; ELECTRIC FIELDS; HOLOGRAPHY; SIMULATION; TRANSMISSION ELECTRON MICROSCOPY

Citation Formats

Beleggia, M., Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Kasama, T., Larson, D. J., Kelly, T. F., Dunin-Borkowski, R. E., and Pozzi, G.. Towards quantitative off-axis electron holographic mapping of the electric field around the tip of a sharp biased metallic needle. United States: N. p., 2014. Web. doi:10.1063/1.4887448.
Beleggia, M., Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Kasama, T., Larson, D. J., Kelly, T. F., Dunin-Borkowski, R. E., & Pozzi, G.. Towards quantitative off-axis electron holographic mapping of the electric field around the tip of a sharp biased metallic needle. United States. doi:10.1063/1.4887448.
Beleggia, M., Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Kasama, T., Larson, D. J., Kelly, T. F., Dunin-Borkowski, R. E., and Pozzi, G.. Mon . "Towards quantitative off-axis electron holographic mapping of the electric field around the tip of a sharp biased metallic needle". United States. doi:10.1063/1.4887448.
@article{osti_22308977,
title = {Towards quantitative off-axis electron holographic mapping of the electric field around the tip of a sharp biased metallic needle},
author = {Beleggia, M. and Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin and Kasama, T. and Larson, D. J. and Kelly, T. F. and Dunin-Borkowski, R. E. and Pozzi, G.},
abstractNote = {We apply off-axis electron holography and Lorentz microscopy in the transmission electron microscope to map the electric field generated by a sharp biased metallic tip. A combination of experimental data and modelling provides quantitative information about the potential and the field around the tip. Close to the tip apex, we measure a maximum field intensity of 82 MV/m, corresponding to a field k factor of 2.5, in excellent agreement with theory. In order to verify the validity of the measurements, we use the inferred charge density distribution in the tip region to generate simulated phase maps and Fresnel (out-of-focus) images for comparison with experimental measurements. While the overall agreement is excellent, the simulations also highlight the presence of an unexpected astigmatic contribution to the intensity in a highly defocused Fresnel image, which is thought to result from the geometry of the applied field.},
doi = {10.1063/1.4887448},
journal = {Journal of Applied Physics},
number = 2,
volume = 116,
place = {United States},
year = {Mon Jul 14 00:00:00 EDT 2014},
month = {Mon Jul 14 00:00:00 EDT 2014}
}
  • Off-axis electron holography employing a field-free Lorentz lens has been used to provide direct imaging of magnetic induction in Nd{sub 2}Fe{sub 14}B with nanometer-scale resolution and high signal-to-noise. Using this technique, reconstructed phase images have been used to measure domain wall widths for 90{degree} and 180{degree} walls in a sintered sample were measured to be no greater than 7 and 9 nm, respectively. Induction maps show an unusual array of 90{degree} domains in a hot-press sample, with singularities at the intersections of the domains. {ital In situ} thermal annealing of the hot-pressed sample resulted in magnetization rotation accompanied by domainmore » wall movement and evidence for pinning at a structural defect. Heating of the sample above 400{degree}C resulted in the accumulation of small particles in thin regions and decrease in magnetic contrast. {copyright} {ital 1998 American Institute of Physics.}« less
  • 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 electricmore » 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.« less
  • Power augmentation and velocity measurements in the wake of a HAWT blade with Mie type tip vane (a tip device on the main blade) are presented. The maximum C{sub p} with a Mie type tip vane is found to be 15% larger than that without the Mie type tip vane. Power augmentation caused by the Mie type tip vane is mainly due to the reduction of tip vortex and the diffusing effect by the Mie type tip vane. The effects of a Mie type tip vane are quantitatively verified by the velocity distributions around the tip of the main blade.more » The velocity distribution was measured by three-dimensional hot wire probes, which measured the axial, radial, and tangential velocity components. The circulation distributions along the main blade with a Mie type tip vane and without a Mie type tip vane were obtained from the measured velocity distributions. A strong reduction of bound vorticity is found for the main blade tip without the Mie type tip vane, whereas the bound vorticity persists on the main blade tip with the Mie type tip vane.« less
  • Precession electron diffraction is an efficient technique to measure strain in nanostructures by precessing the electron beam, while maintaining a few nanometre probe size. Here, we show that an advanced diffraction pattern treatment allows reproducible and precise strain measurements to be obtained using a default 512 × 512 DigiSTAR off-axis camera both in advanced or non-corrected transmission electron microscopes. This treatment consists in both projective geometry correction of diffraction pattern distortions and strain Delaunay triangulation based analysis. Precision in the strain measurement is improved and reached 2.7 × 10{sup −4} with a probe size approaching 4.2 nm in diameter. This method is applied to themore » study of the strain state in InGaAs quantum-well (QW) devices elaborated on Si substrate. Results show that the GaAs/Si mismatch does not induce in-plane strain fluctuations in the InGaAs QW region.« less