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Updated: May 21, 2025
08:04
Preparation and Observation of Thick Biological Samples by Scanning Transmission Electron Tomography
Published on: March 12, 2017
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Mass-Thickness Measurements in the Transmission Electron Microscope: A Single-Standard Approach to Quantitative EDS
Thomas J Zega1, Jane Y Howe2, Devin L Schrader3
1Lunar and Planetary Laboratory, Materials Science and Engineering, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721, USA.
Summary
Optimizing X-ray analysis in scanning transmission electron microscopy (STEM) is crucial for materials science. Adjusting sample holder orientation minimizes X-ray shadowing, achieving high accuracy for quantitative compositional analysis.
Area of Science:
- Materials Science
- Analytical Chemistry
- Electron Microscopy
Background:
- Quantitative compositional analysis using energy-dispersive X-ray spectroscopy (EDS) in scanning transmission electron microscopy (STEM) is vital for materials characterization.
- Focused ion beam (FIB) preparation is commonly used for creating electron-transparent samples, but can introduce artifacts affecting analysis.
Purpose of the Study:
- To evaluate a single-standard approach for quantitative EDS analysis on FIB-prepared SrTiO3, CaTiO3, and Fe sulfide samples.
- To investigate and mitigate the impact of X-ray shadowing on quantitative EDS accuracy.
- To optimize analytical geometry for improved precision and accuracy in STEM-EDS.
Main Methods:
- Quantitative EDS analysis was performed on FIB sections of SrTiO3, CaTiO3, and Fe sulfides using a STEM.
- X-ray shadowing effects were mapped and analyzed.
- Sample holder orientation in the transmission electron microscope was adjusted to optimize the line-of-sight to the EDS detector.
- Results were compared with quantitative wavelength-dispersive spectrometry (WDS) from an electron microprobe.
Main Results:
- Shadowing of X-rays was confirmed as a significant factor affecting quantitative EDS analysis.
- Adjusting the orientation of FIB half grids in the STEM sample holder effectively minimized X-ray occlusion.
- A precision of 2% was achieved when comparing STEM-EDS data with electron microprobe WDS.
- Accuracies within 5% of stoichiometric composition were obtained with optimized analytical geometry.
Conclusions:
- Optimized analytical geometry, specifically sample holder orientation, is critical for accurate quantitative EDS analysis in STEM.
- The single-standard approach, when combined with optimized geometry, provides reliable compositional data for materials science applications.
- This method offers a pathway to achieve high-precision, accurate elemental quantification in FIB-prepared samples.
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