Towards quantitative, atomic-resolution reconstruction of the electrostatic potential via differential phase contrast using electrons

Differential phase contrast images in scanning transmission electron microscopy can be directly and quantitatively related to the gradient or the projected specimen potential provided that (a) the specimen can be treated as a phase object and (b) loll 20 diffraction patterns as a function of probe position can be obtained. Both are challenging to achieve in atomic resolution imaging. The former is fundamentally limited by probe spreading and dynamical electron scattering, and we explore its validity domain in the context of atomic resolution differential phase contrast imaging. The latter, for which proof-of-principle experimental data sets exist, is not yet routine. We explore the extent to which more established segmented detector geometries can instead be used to reconstruct a quantitatively good approximation to the projected specimen potential. (C) 2015 Elsevier B.V. All rights reserved