Orientation mapping of graphene using 4D STEM-in-SEM.

Area of Science:

• Materials Science
• Electron Microscopy
• Nanotechnology

Background:

• Scanning electron microscopy (SEM) is a powerful tool for surface imaging.
• Transmission electron microscopy (TEM) provides high-resolution structural information through diffraction patterns.
• Integrating diffraction capabilities into SEM can enhance nanoscale material characterization.

Purpose of the Study:

• To implement and validate a 4D STEM-in-SEM technique for advanced materials analysis.
• To assess the sensitivity, spatial resolution, and angular precision of the developed technique.
• To demonstrate the applicability of 4D STEM-in-SEM for characterizing graphene structures.

Main Methods:

• Implementation of a 4D STEM technique within a scanning electron microscope.
• Utilizing an on-axis lens-coupled phosphor/CCD detector for diffraction pattern acquisition.
• Employing off-the-shelf data acquisition hardware for synchronized beam and camera control.
• Graphene as a model system for instrumentation testing and analysis technique development.

Main Results:

• Interpretable diffraction patterns obtained from monolayer graphene with short integration times (0.5 ms) and low electron doses.
• High data acquisition rates (approx. 100/s) enabling analysis across multiple length scales (mm to nm).
• Demonstrated spatial resolution of ≤5.6 nm and angular precision of ≤0.19° for unsupported monolayer graphene.
• Successful analysis of complex multilayer graphene films using the 4D datasets.

Conclusions:

• The 4D STEM-in-SEM technique is sensitive and effective for nanoscale material characterization.
• The technique offers high spatial resolution and angular precision, suitable for detailed structural analysis.
• 4D STEM-in-SEM provides rich information for complex heterogeneous materials like multilayer graphene.