Direct Visualization of Local Electromagnetic Field Structures by Scanning Transmission Electron Microscopy

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology
• Electron Microscopy

Background:

• Material and device properties are governed by internal electromagnetic fields, particularly at interfaces and surfaces.
• Understanding these fields is crucial for explaining exotic material behaviors and optimizing device performance.
• Direct characterization of local electromagnetic fields at atomic dimensions has been a significant challenge.

Purpose of the Study:

• To present an overview of the development and application of differential phase contrast (DPC) microscopy for aberration-corrected scanning transmission electron microscopy (STEM).
• To demonstrate the capability of DPC STEM for directly imaging electromagnetic field structures in materials and devices at high resolution.
• To explore the potential of DPC STEM for atomic-resolution imaging and understanding intra- and interatomic electronic structures.

Main Methods:

• Development of segmented-type STEM detectors enabling simultaneous acquisition of multiple images sensitive to electron scattering angles.
• Application of aberration-corrected STEM with sub-angstrom electron probes.
• Utilizing differential phase contrast (DPC) microscopy principles for electromagnetic field mapping.

Main Results:

• DPC STEM successfully visualized local electric field variations across p-n junctions in semiconductors, unobservable with conventional STEM modes.
• Imaging of magnetic domains and skyrmions in magnetic materials was achieved with high clarity.
• Atomic-resolution imaging revealed atomic electric fields, providing insights into atomic species, chemical bonding, and charge redistribution.

Conclusions:

• Differential phase contrast (DPC) microscopy combined with aberration-corrected scanning transmission electron microscopy (STEM) is a powerful tool for directly imaging electromagnetic fields in materials.
• The technique offers unprecedented insights into material properties at the nanoscale and atomic scale.
• Future applications may include novel methods for visualizing atoms and nanostructures based on their electromagnetic field signatures.