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Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy
Published on: February 5, 2017
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Measuring nanometre-scale electric fields in scanning transmission electron microscopy using segmented detectors.
H G Brown1, N Shibata2, H Sasaki3
1School of Physics and Astronomy, Monash University, Victoria 3800, Australia.
Ultramicroscopy
|July 11, 2017
Summary
Quantitative electric field mapping in scanning transmission electron microscopy (STEM) is improved for thick specimens. New methods correct for detector limitations and scattering, enabling accurate nanoscale electric potential reconstruction.
Area of Science:
- Materials Science
- Electron Microscopy
- Condensed Matter Physics
Background:
- Nanoscale electric field mapping in scanning transmission electron microscopy (STEM) is advancing.
- Quantitative analysis of these measurements, especially in thick specimens, faces challenges due to unclear assumptions.
- Existing methods struggle with detector segment size, inelastic scattering, and boundary conditions.
Purpose of the Study:
- To evaluate and improve quantitative electric potential reconstruction methods using segmented detectors in STEM.
- To address limitations of current approaches, particularly for thick samples.
- To develop reliable calibration and correction strategies for accurate field measurements.
Main Methods:
- Investigated three quantitative reconstruction approaches: segmented detector approximation to differential phase contrast (DPC) and two ptychographical methods.
- Analyzed limitations including detector segment size, inelastic scattering, and non-periodic boundary conditions.
- Developed a calibration experiment for DPC and scattering corrections for both DPC and ptychography.
Main Results:
- A simple calibration experiment successfully corrected DPC reconstructions for finite detector segments and plasmon scattering in thick specimens.
- Plasmon scattering corrections were also applied to segmented detector ptychography approaches.
- Reconstructions avoiding periodic boundary conditions demonstrated more realistic projected electric potentials.
Conclusions:
- Quantitative electric field mapping in STEM is achievable even for thick specimens with appropriate corrections.
- The developed calibration and correction methods enhance the reliability of nanoscale electric potential measurements.
- Avoiding periodic boundary conditions is crucial for accurate and realistic reconstructions in electron microscopy.
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