2D strain mapping using scanning transmission electron microscopy Moiré interferometry and geometrical phase...

Area of Science:

• Materials Science
• Nanotechnology
• Electron Microscopy

Background:

• Accurate strain characterization is crucial for understanding material properties.
• Conventional methods in scanning transmission electron microscopy (STEM) have limitations in field of view for strain mapping.

Purpose of the Study:

• To demonstrate a novel strain characterization technique using STEM Moiré interferometry and geometrical phase analysis (GPA).
• To extend the capabilities of high-resolution STEM GPA for quantitative 2D strain mapping over larger areas.

Main Methods:

• Utilized Moiré interferometry within a STEM setup to capture deformation fields in STEM Moiré holograms.
• Applied sampling theory and STEM electron micrograph references to simulate Moiré patterns and extract crystal lattice information.
• Employed geometrical phase analysis (GPA) to extract 2D relative strain and rotation fields from the processed data.

Main Results:

• Successfully demonstrated a technique combining STEM Moiré interferometry and GPA for strain characterization.
• Achieved de-magnification of local information to a large length scale, comparable to dark-field electron holography.
• Extended conventional STEM GPA by enabling quantitative 2D strain mapping with a field of view up to a few microns.

Conclusions:

• The developed STEM Moiré GPA method offers enhanced capabilities for materials characterization.
• This technique provides a valuable tool for analyzing strain distributions in materials with a larger field of view.
• The method bridges the gap between high-resolution local analysis and broader area characterization in electron microscopy.