High-resolution elastic strain measurement from electron backscatter diffraction patterns: new levels of sensitivity

Area of Science:

• Materials Science
• Crystallography
• Electron Microscopy

Background:

• Electron Backscatter Diffraction (EBSD) is a crucial technique for analyzing crystal orientation and microstructure.
• Accurate measurement of strain and rotation is essential for understanding material deformation and performance.
• Traditional EBSD methods have limitations in precisely quantifying localized strain variations.

Purpose of the Study:

• To demonstrate a cross-correlation based method for accurately measuring shifts in EBSD patterns.
• To quantify strain and rotation tensor variations from wide-angled EBSD patterns.
• To analyze strain distribution at the interface of semiconductor heterostructures.

Main Methods:

• Utilized cross-correlation algorithms to measure feature shifts in EBSD patterns with sub-pixel accuracy (+/- 0.05 pixels).
• Applied the method to wide-angled EBSD patterns to determine the full strain and rotation tensor.
• Investigated strain variations across a Si1-xGex epilayer on a Si substrate interface.

Main Results:

• Achieved high precision in measuring pattern shifts, corresponding to minimal angular changes (8.5 x 10(-5) rad).
• Demonstrated a standard deviation of 1.3 x 10(-4) for rotation measurements on single crystals.
• Observed significant tensile strains and lattice curvature in the epilayer extending into the substrate, with localized shear strains at the interface.

Conclusions:

• Cross-correlation EBSD is a highly sensitive method for quantifying lattice strain and rotation.
• The technique allows for detailed analysis of deformation mechanisms in materials, including semiconductor interfaces.
• EBSD offers a unique combination of high strain sensitivity, spatial resolution, and ease of use for materials characterization.