Sampling optimization of Moiré geometrical phase analysis for strain characterization in scanning transmission...

Area of Science:

• Materials Science
• Electron Microscopy
• Solid State Physics

Background:

• Scanning Transmission Electron Microscope Geometric Phase Analysis (STEM GPA) is a powerful technique for strain mapping.
• STEM Moiré GPA (SMG) offers large field-of-view deformation mapping by utilizing aliasing artifacts.
• Current SMG methods lack precise parameter selection, potentially leading to inaccurate results.

Purpose of the Study:

• To develop and validate a procedure for optimizing sampling parameters (pixel spacing and scanning rotation) for SMG.
• To ensure the reliability of SMG for accurate strain characterization in single crystal materials.
• To compare SMG results with established High-Resolution STEM GPA.

Main Methods:

• Development of an optimization procedure for STEM Moiré hologram acquisition.
• Application of the optimization procedure to an InP/InAs$_{1-x}$P$_{x}$/InP heterostructure.
• Comparison of SMG-derived deformation profiles with High-Resolution STEM GPA data.

Main Results:

• The proposed procedure enables optimal selection of pixel spacing and scanning rotation for SMG.
• Optimized SMG provides reliable deformation mapping comparable to conventional STEM GPA.
• The study demonstrates the effectiveness of SMG for large-scale strain analysis.

Conclusions:

• The optimized SMG technique is a reliable and efficient method for large field-of-view strain characterization.
• The developed optimization protocol addresses limitations of previous empirical recommendations for SMG.
• A generalized coherent sampling concept is proposed for advanced electron microscopy applications.