Three-dimensional imaging in double aberration-corrected scanning confocal electron microscopy, part I: elastic...

Area of Science:

• Materials Science
• Electron Microscopy
• Nanotechnology

Background:

• Spherical aberration correctors in transmission electron microscopy enable advanced imaging techniques.
• Confocal microscopy principles can be adapted to electron microscopy for enhanced resolution and contrast.

Purpose of the Study:

• To investigate the image contrast properties of elastically scattered electrons in aberration-corrected scanning confocal electron microscopy (AC-SEM).
• To evaluate the potential of AC-SEM for atomic-resolution imaging and the detection of subsurface features.

Main Methods:

• Utilizing a transmission electron microscope equipped with pre- and post-specimen spherical aberration correctors.
• Performing multislice simulations to model electron scattering and image formation in crystalline samples.
• Analyzing image contrast generated by elastically scattered electrons under confocal conditions.

Main Results:

• Absence of linear phase contrast in the confocal condition results in minimal contrast for single atoms.
• Accurate determination of sample vertical location and thickness is achievable for thicker crystalline samples.
• Buried impurity layers exhibit weak and difficult-to-interpret contrast.

Conclusions:

• AC-SEM with elastically scattered electrons is effective for structural analysis of thicker samples but less so for single atoms or buried impurities.
• Further research is needed to optimize contrast mechanisms for subsurface defect imaging.
• The accompanying paper explores the use of inelastically scattered electrons in this configuration.