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Comparison of detectability limits for elemental mapping by EF-TEM and STEM-XEDS
Masashi Watanabe1, David B Williams, Yoshitsugu Tomokiyo
1Department of Materials Science and Engineering, Lehigh University, Bethlehem, PA 18015, USA.
Micron (Oxford, England : 1993)
|August 5, 2003
Summary
Energy filter transmission electron microscopy (EF-TEM) offers higher analytical sensitivity for elemental mapping in thin specimens compared to scanning transmission electron microscopy with X-ray energy dispersive spectrometry (STEM-XEDS). However, STEM-XEDS provides better detectability limits for thicker Cu-Mn alloy samples.
Area of Science:
- Materials Science
- Analytical Chemistry
- Electron Microscopy
Background:
- Elemental mapping is crucial for analyzing material composition at the nanoscale.
- Transmission electron microscopy (TEM) techniques like EF-TEM and STEM-XEDS are widely used for elemental analysis.
- Understanding the analytical sensitivity and detectability limits of these techniques is essential for accurate material characterization.
Purpose of the Study:
- To compare the analytical sensitivity and detectability limits of EF-TEM and STEM-XEDS for elemental mapping.
- To investigate the influence of specimen thickness on the signal-to-noise ratio (SNR) and minimum mass fraction (MMF) in both techniques.
- To determine which technique offers superior performance under different specimen thickness conditions.
Main Methods:
- Elemental mapping was performed using EF-TEM and STEM-XEDS on homogeneous Cu-Mn thin specimens.
- Analytical sensitivity was evaluated by measuring spectral signal-to-noise ratio (SNR) at various confidence limits (1, 2, and 3 sigma).
- A method was developed to estimate the minimum mass fraction (MMF) from signal and background intensities to assess detectability limits.
Main Results:
- EF-TEM mapping demonstrated higher analytical sensitivity for specimen thicknesses below approximately 50 nm, especially at higher confidence limits.
- STEM-XEDS mapping showed improved spectral SNR with increasing specimen thickness.
- For thicker specimens (>50 nm), STEM-XEDS provided better detectability limits for elemental mapping in Cu-Mn dilute alloys.
Conclusions:
- EF-TEM is more sensitive for elemental mapping of thin specimens, while STEM-XEDS is more effective for thicker samples.
- Specimen thickness is a critical factor influencing the choice of technique for optimal elemental mapping sensitivity.
- The developed MMF estimation method allows for a quantitative comparison of analytical sensitivity between different elemental mapping techniques.