Quantitative STEM normalisation: The importance of the electron flux

Area of Science:

• Materials Science
• Physics
• Chemistry

Background:

• Annular dark-field scanning transmission electron microscopy (ADF-STEM) is crucial for quantitative studies, enabling direct comparison of experimental and simulated images.
• Accurate normalization of experimental data to 'fractional beam-current' is essential for quantitative ADF-STEM.
• Detector response inhomogeneities complicate normalization, making quantification instrument-specific and computationally intensive.

Purpose of the Study:

• To propose an alternative method for normalizing experimental ADF-STEM data for comparison with simulations assuming a homogeneous detector response.
• To simplify the quantification procedure in ADF-STEM, reducing reliance on instrument-specific simulations.

Main Methods:

• Determined electron flux distribution reaching the detector using a camera-length series or atomic column cross-section averaged convergent beam electron diffraction (XSACBED) patterns.
• Utilized the electron flux distribution to determine the relative weighting of the detector response.
• Introduced the electron flux weighted (EFW) method for data normalization.

Main Results:

• The EFW method yields results comparable to the currently used normalization method.
• The proposed method significantly simplifies the required simulation libraries.
• The EFW method provides a metric to assess detector response quality against an ideal response.

Conclusions:

• The electron flux weighted (EFW) method offers a simplified and effective approach to normalizing experimental ADF-STEM data for quantitative analysis.
• This method facilitates inter-instrument and inter-research group comparisons by reducing the need for complex, instrument-specific simulations.
• The EFW method enhances the accessibility and efficiency of quantitative ADF-STEM studies.