Characterization of extended defects in 2D materials using aperture-based dark-field STEM in SEM

Area of Science:

• Materials Science
• Electron Microscopy
• Nanotechnology

Background:

• Quantitative diffraction contrast analysis is crucial for studying crystalline material defects using transmission electron microscopy (TEM).
• Similar transmission techniques were previously unavailable for scanning electron microscopy (SEM) platforms.
• Studying defects in 2D materials is challenging due to difficulties in establishing two-beam conditions for standard analysis.

Purpose of the Study:

• To adapt aperture-based dark-field imaging from TEM to SEM for quantitative diffraction contrast studies.
• To enable lower-voltage defect analysis in SEM, particularly for 2D materials.
• To demonstrate the method's capability for reliable Burgers vector analysis of dislocations.

Main Methods:

• Transferring aperture-based dark-field imaging to SEM operating in scanning transmission electron microscopy (STEM) mode.
• Utilizing a custom-made aperture between the sample and STEM detector to select specific diffraction reflections.
• Employing the Low Energy Nanodiffraction (LEND) setup to capture transmission diffraction patterns.

Main Results:

• Successful implementation of aperture-based dark-field STEM for quantitative diffraction contrast analysis at lower SEM voltages.
• Demonstration of the method's efficacy in studying basal plane dislocations in bilayer graphene.
• Validation of reliable Burgers vector analysis using the g·b=0 invisibility criterion, confirmed by comparison with TEM results.

Conclusions:

• The developed aperture-based dark-field STEM method provides a viable alternative to TEM for quantitative defect analysis.
• This technique is particularly advantageous for studying extended defects in 2D materials where traditional methods are insufficient.
• The method allows for reliable Burgers vector determination, crucial for understanding the properties of materials like graphene.