Subset geometric phase analysis method for deformation evaluation of HRTEM images

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Geometrical Phase Analysis (GPA) is a key technique for analyzing deformation in high-resolution transmission electron microscopy (HRTEM) images.
• Traditional global-GPA (G-GPA) relies on Fast Fourier Transform (FFT) and relates displacement to phase difference.
• Limitations in G-GPA include susceptibility to phase filling effects and accuracy constraints.

Purpose of the Study:

• To introduce and validate a novel subset-Geometrical Phase Analysis (S-GPA) method for enhanced deformation analysis in HRTEM.
• To theoretically analyze the maximum strain measurement scale of GPA methods.
• To compare the performance of S-GPA against traditional G-GPA under various deformation conditions.

Main Methods:

• Implementation of S-GPA using windowed Fourier transform applied block-by-block on images.
• Theoretical analysis of the phase spectrum extraction process to determine the maximum strain measurement scale.
• Numerical simulations to evaluate S-GPA and G-GPA performance for homogeneous and inhomogeneous deformations.
• Application of S-GPA to analyze strain distribution in an InGaAs/InAlAs superlattice heterostructure.

Main Results:

• S-GPA demonstrates superior performance over G-GPA in both homogeneous and inhomogeneous deformation scenarios.
• Calculation reliability of S-GPA is 10% higher than G-GPA.
• S-GPA achieves approximately three times higher measurement accuracy than G-GPA for small strains (<2000με) and 50% higher for large strains (>150000με).
• S-GPA effectively eliminates the phase filling effect, a limitation of G-GPA.

Conclusions:

• The developed S-GPA method offers significant improvements in accuracy and reliability for deformation analysis in HRTEM.
• S-GPA extends the measurable strain range and overcomes limitations of traditional G-GPA.
• S-GPA is a powerful tool for detailed strain field analysis, as demonstrated by its application to semiconductor heterostructures.