Imaging domains in BaTiO3 single crystal nanostructures: comparing information from transmission electron microscopy and piezo-force microscopy

This article compares and contrasts information<br/>obtained, using transmission electron microscopy (TEM)<br/>and piezo-force microscopy (PFM), on domain configurations<br/>adopted in single crystal lamellae of BaTiO3, that had<br/>been cut directly from bulk using a focused ion beam<br/>microscope with top and bottom surfaces parallel to<br/>{100}pseudocubic. Both forms of imaging reveal domain<br/>walls parallel to {110}pseudocubic, consistent with sets of 90<br/>domains with dipoles oriented parallel to the two<br/>\001[pseudocubic directions in the plane of the lamellae.<br/>However, the domain width was observed to be dramatically<br/>larger using PFM than it was using TEM. This suggests<br/>significant differences in the surface energy densities<br/>that drive the domain formation in the first place, that could<br/>relate to differences in the boundary conditions in the two<br/>modes of imaging (TEM samples are imaged under high<br/>vacuum, whereas PFM imaging was performed in air).<br/>Attempts were made to map local dipole orientations<br/>directly, using a form of ‘vector’ PFM. However, information<br/>inferred was largely inconsistent with the known<br/>crystallography of the samples, raising concern about the<br/>levels of care needed for accurate interpretation of PFM<br/>images.