The observation of the charge distribution on domain walls via inline holography

Ferroelectric charged domain walls are promising elements of future nanoelectronic devices because their bound charges can modulate electrostatic potential and carrier transport. In-line electron holography provides a low-dose and noninvasive approach for visualizing such charge-related electrostatic fields through phase retrieval. In-line holography is distinguished by its flexible exposure conditions, robust phase reconstruction and wide-field potential-mapping capability among charge characterization approaches. However, the direct observation of charged domain walls remains a major challenge using weak-phase imaging methods, because the phase shift is not only determined by electrostatic fields but can also be influenced by finite field-of-view effects, boundary effects, and nonlinear diffraction contrast. Here, based on in-line electron holography, we address these limitations to map charge distributions at domain walls in epitaxial PbTiO 3 thin films. To reduce phase contributions unrelated to the intrinsic bound charges, we establish a strategy that integrates Fourier boundary padding, objective-aperture-based reciprocal-space selection and off-zone-axis incidence to minimize interference from diffraction effects. This strategy reduces non-charge-related phase shifts from nonlinear diffraction while retaining the bound-charge-induced electrostatic phase signal. The approach enables direct determination of the charge distribution of 90° domain walls in PbTiO 3 , which can be corroborated by polar map. This work provides a reliable and generalizable approach for observing local charge distributions in oxide thin films and interfaces, and may further enable the capability of observing the dynamics behavior of domain walls.