Atomic resolution HOLZ-STEM imaging of atom position modulation in oxide heterostructures

Area of Science:

• Materials Science
• Solid-State Physics
• Electron Microscopy

Background:

• Higher order Laue zone (HOLZ) rings in electron diffraction are sensitive to atomic column arrangements.
• Individual atom columns within a crystal structure exhibit unique HOLZ ring characteristics.

Purpose of the Study:

• To investigate the atomic structure of a perovskite trilayer using atomic resolution.
• To demonstrate the capability of HOLZ-STEM for analyzing 3D periodicity in crystalline materials.

Main Methods:

• Acquisition of an atomic resolution 4-dimensional scanning transmission electron microscopy (4D-STEM) dataset.
• Utilizing multislice simulations for detailed analysis of experimental diffraction patterns.
• Comparing experimental HOLZ ring data with simulated patterns to interpret structural features.

Main Results:

• Observed distinct HOLZ ring patterns for La-O, O, and Fe columns in the perovskite trilayer.
• A strong HOLZ ring indicated significant La position modulation along the <110> direction.
• Weaker HOLZ rings were observed for O and Fe columns, correlating with their atomic positions.

Conclusions:

• Atomic resolution HOLZ-STEM is a viable technique for probing the 3D periodicity of crystalline materials.
• HOLZ ring analysis provides insights into atomic position modulation within crystal structures.
• The study successfully identified period doubling in the central LaFeO3 layer of the perovskite trilayer.