Nondestructive Mapping of Long-Range Dislocation Strain Fields in an Epitaxial Complex Metal Oxide
Hugh Simons1, Anders Clemen Jakobsen1, Sonja Rosenlund Ahl1
1Department of Physics , Technical University of Denmark , Kgs. Lyngby 2800 , Denmark.
Nano Letters
|February 7, 2019
Summary
Misfit dislocations in ferroic oxides create strain fields impacting device performance. Dark-field X-ray microscopy precisely quantifies these weak, long-range strains and associated charge heterogeneities in bismuth ferrite films.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Heteroepitaxial interfaces generate misfit dislocations, causing strain fields beyond epitaxial strain.
- Strong lattice coupling in ferroic oxides, like bismuth ferrite, leads to unpredictable functionality due to these strain fields.
- Understanding strain distribution is crucial for optimizing device performance in advanced materials.
Purpose of the Study:
- To map and quantify lattice distortions around misfit dislocations in epitaxial bismuth ferrite films.
- To investigate the impact of dislocation components (screw and edge) on strain and charge heterogeneities.
- To establish physical limitations on device scaling and material design in epitaxial systems.
Main Methods:
- Utilized dark-field X-ray microscopy for high-resolution imaging of lattice distortions.
- Employed strain quantification techniques to measure weak, long-ranging strain fields without altering the film's mechanical state.
- Isolated screw and edge dislocation components to analyze their individual contributions.
Main Results:
- Precisely quantified weak, long-ranging strain fields and symmetry lowering around misfit dislocations.
- Demonstrated that screw and edge dislocations induce charge heterogeneities through flexoelectric coupling.
- Observed measurable charge and strain heterogeneities extending over mesoscopic scales, even with small lattice mismatches and stress relief mechanisms.
Conclusions:
- Misfit dislocations significantly impact ferroic oxide properties, even under conditions of small lattice mismatch and stress relief.
- Flexoelectric coupling plays a key role in generating charge heterogeneities from strain fields.
- Findings impose stricter physical limitations on device size, dislocation density, and lattice mismatch in epitaxial systems.
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