Investigating the convergence properties of iterative ptychography for atomic-resolution low-dose imaging

Area of Science:

• Materials Science
• Physics
• Chemistry

Background:

• Iterative electron ptychography is a powerful technique for high-resolution imaging.
• Low electron doses are desirable to minimize sample damage but can challenge reconstruction accuracy.

Purpose of the Study:

• To investigate the convergence properties of iterative electron ptychography methods under low electron doses.
• To determine the impact of user-defined update strengths on reconstruction accuracy and convergence.

Main Methods:

• Analysis of iterative electron ptychography algorithms with varying update strengths.
• Application to a 4D dataset of a hybrid organic-inorganic formamidinium lead bromide (FAPbBr3) sample.
• Evaluation of reconstruction error and convergence behavior.

Main Results:

• Carefully chosen, smaller update strengths are essential for accurate reconstructions of projected electrostatic potential.
• Convergence is achievable with relatively small object and probe update strengths under low electron doses.
• Reducing update strengths below a critical threshold increases initial error and can trap algorithms in local minima.

Conclusions:

• Optimized reconstruction parameters, particularly smaller update strengths, are critical for successful iterative electron ptychography at low electron doses.
• The findings emphasize the need for parameter tuning to ensure both effective convergence and result correctness.
• This work provides guidance for improving electron ptychography reconstructions in sensitive materials.