Electron Channeling Contrast Imaging of Ferroelastic Domains.

Ferroelastic phase transitions lead to the formation of ferroelastic twins, resulting in spatial inhomogeneities in the crystal structures and functional properties of ferroelastic materials. Despite the importance of such nanoscale twins in oxide heterostructures, their direct, non-invasive observation has relied on cumbersome and low-throughput techniques such as transmission electron microscopy and synchrotron X-ray diffraction, or been restricted to materials with coexistence of ferroelectric and ferroelastic states, by detecting the coupled ferroelectric order. In this study, the application of electron channeling contrast imaging (ECCI) in a scanning electron microscope for imaging ferroelastic domains in various oxide heterostructures is demonstrated. These include systems where ferroelasticity is coupled with critical functional properties such as ferroelectricity, magnetism and charge transport. The versatility of this imaging method is highlighted across different heterostructure geometries, from bare thin films to multilayers, achieving an impressive resolution of 6 nm. ECCI presents a powerful approach for exploring the rich spectrum of ferroelasticity-coupled phenomena in oxide heterostructures.