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Figure 3. (A) Atomic resolution images of SrTiO viewed along the [001] direction with ABF (11-22 mrad), BF (0-22 mrad), and ADF
3
(90-170 mrad) STEM images. Adapted with permission [33] . Copyright © 2012 Elsevier. (B) DPC detector configuration with
accompanying A-C and B-D STEM images of the ferroelectric Pb(Zr Ti )O thin films. Contrast resulting from the ferroelectric
0.2 0.8 3
domain structures in Pb(Zr Ti )O are visible. Reprinted with permission [34] Copyright © 2021 MDPI. (C) Atomic resolution iDPC
0.2 0.8 3
images of gallium nitride (GaN) oriented along the [11 0] and [10 1] orientations. Reprinted with permission [35] . Copyright © 2018
Nature Publishing Group.
[20]
carefully tilted on a zone axis for optimal imaging . Despite the challenges involved in imaging light
elements, the ability to do so simultaneously with other imaging modes, such as ADF imaging, offers a
powerful method for characterizing atomic structures and chemistry at the atomic scale. For instance,
simultaneous ADF and iDPC imaging were employed to investigate the atomic structure of the relaxor
ferroelectric PMN-PT with varying Ti content. This allowed for a direct correlation of local chemistry with
polarization, octahedral distortion, and octahedral tilting . These observations are crucial for
[40]
understanding the origin of relaxor ferroelectricity and providing insights into how local structures can be
engineered to optimize material properties.

Direct electron detectors and four-dimensional STEM
In the last decade, four-dimensional STEM (4D-STEM) has attracted significant research interest, given its
plentiful prospects for material analysis. Conventional STEM detector technology converts the electrons
collected at each pixel into a single value representing the contrast. While this number can be expanded
upon by using segmented detectors, 4D-STEM refers to the recording of 2D images of the electron probe at
each pixel in a 2D image, as illustrated in Figure 1C [19,41,42] . Although there are numerous detector
configurations that can be utilized for the collection of 4D-STEM, one of the most widely available detectors
is the electron microscope pixel array detector (EMPAD), which is manufactured by Thermofisher
Scientific. The EMPAD is composed of a collection of photodiodes arranged on an integrated circuit that