High precision measurements of atom column positions using model-based exit wave reconstruction

Area of Science:

• Materials Science
• Electron Microscopy
• Computational Imaging

Background:

• Accurate determination of atomic positions is crucial for understanding material properties.
• Traditional methods often face limitations in precision and computational efficiency.
• Maximizing information from electron microscopy focal series is an ongoing challenge.

Purpose of the Study:

• To investigate methods for accurate and precise measurement of atom column positions.
• To compare maximum likelihood estimation (MLE) with other reconstruction techniques.
• To introduce a novel real-space model-based exit wave reconstruction method.

Main Methods:

• Utilizing a focal series of images in transmission electron microscopy (TEM).
• Applying maximum likelihood estimation (MLE) to the full series of focal images.
• Developing and applying a real-space model-based exit wave reconstruction technique grounded in channelling theory.

Main Results:

• Simulations demonstrate that a reconstructed complex exit wave retains information on atom column positions comparable to the full focal series.
• Maximum likelihood estimation theoretically achieves the lower bound on position variances.
• Information retrieval from the reconstructed wave's phase is effective for thin samples (weak phase objects).

Conclusions:

• A computationally intensive MLE approach can attain theoretical precision limits for atom column positioning.
• A novel real-space reconstruction method effectively captures positional information.
• The phase of the reconstructed exit wave is key for precise measurements in thin samples.