Systematic Errors of Electric Field Measurements in Ferroelectrics by Unit Cell Averaged Momentum Transfers in STEM

Abstract When using the unit cell average of first moment data from four-dimensional scanning transmission electron microscopy (4D-STEM) to characterize ferroelectric materials, a variety sources systematic errors needs be taken into account. In particular, these are magnitude acceleration voltage, STEM probe semi-convergence angle, sample thickness, and tilt out zone axis. Simulations show that error calculated electric fields averaged momentum transfer originates violation point symmetry within cells. Thus, values can easily exceed those potential polarization-induced in ferroelectrics. Importantly, this produces deflection gradients between different domains seemingly representing measured fields. However, it could shown for PbZr0.2Ti0.8O3, many adjacent exhibit relative crystallographic mistilt in-plane rotation. The experimental results method gives qualitative domain contrast. Comparison field with showed contrast is mainly caused by dynamical scattering effects plays only minor role, if present at all.