Quantitative composition determination by ADF-STEM at a low-angular regime: a combination of EFSTEM and 4DSTEM

Area of Science:

• Materials Science
• Nanotechnology
• Electron Microscopy

Background:

• High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) is crucial for nanomaterial composition but struggles with light elements.
• Light elements scatter inefficiently at high angles, limiting HAADF-STEM's utility for certain material systems.
• Static atomic displacements (SADs) in alloys with light elements further complicate low-angle scattering analysis.

Purpose of the Study:

• To develop and validate a method for accurate composition determination of nanomaterials containing light elements at low scattering angles.
• To address discrepancies between experimental data and simulations in low-angle electron microscopy.
• To enable nanoscale analysis of functional materials with light elements, particularly those exhibiting SADs.

Main Methods:

• Utilized low-angle scattering in transmission electron microscopy for light element analysis.
• Resolved discrepancies in quantitative matching by accounting for factors like inelastic scattering and phonon movement in simulations.
• Employed a combination of an in-column energy filter and a fast pixelated detector.

Main Results:

• Achieved an outstanding agreement between simulations and experimental results at low scattering angles.
• Successfully applied the method to quantify GaN_xAs_1-x quantum wells.
• Demonstrated good agreement between transmission electron microscopy (TEM) results and high-resolution X-ray diffraction data.

Conclusions:

• The developed method enables accurate nanoscale composition determination of materials containing light elements, even with SADs.
• This technique enhances the capability of electron microscopy for analyzing complex functional nanomaterials.
• The findings pave the way for more precise characterization of semiconductor alloys and related materials.