Quantitative electric field mapping in thin specimens using a segmented detector: Revisiting the transfer function for differential phase contrast

- We explore the capability of electromagnetic fields quantification by differential phase contrast (DPC) using a multi-segment detector via simulation.
- Combination of the first moment detection concept with the control of contrast transfer function can effectively suppress errors.
- The quantification errors for single atoms of all elements can be less than 1%.

Differential phase contrast in scanning transmission electron microscopy can visualize local electromagnetic fields inside specimens. The contrast derived from first moments, the so-called center of mass, of the diffraction patterns for each probe position can be quantitatively related to the local electromagnetic field under the phase object approximation. While only approximate first moments can be obtained with a segmented detector, in weak phase objects the fields can be accurately quantified on the basis of a phase contrast transfer function. Through systematic image simulations we further show that the quantification based on the approximated first moment is a good approximation also for strong phase objects.